THE ENERGY-smart house
From the Editors of Fine Homebuilding
builder - tested code approved
THE ENERGYSMART HOUSE from the editors of
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Text © 2011 by the Taunton Press, Inc. Photographs © 2011 by the Taunton Press, Inc., except where noted Illustrations © 2011 by the Taunton Press, Inc., except where noted All rights reserved.
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The Taunton Press Inc., 63 South Main St., PO Box 5506, Newtown, CT 06470-5506 e-mail: [emailprotected] Editor: Alex Giannini Copy editor: Seth Reichgott Technical editor: Joseph R. Provey Indexer: Lynda Stannard Cover design: Alison Wilkes Interior design: Cathy Cassidy Layout: Cathy Cassidy Fine Homebuilding® is a trademarks of The Taunton Press Inc., registered in the U.S. Patent and Trademark Office. Library of Congress Cataloging-in-Publication Data The energy-smart house / from the editors of Fine homebuilding. p. cm. Includes index. E-Book ISBN 978-1-62710-082-3 1. Dwellings--Energy conservation. 2. Energy auditing. I. Fine homebuilding. TJ163.5.D86E545 2011 644--dc23 2011023844 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 The following manufacturers/names appearing in The Energy-Smart House are trademarks: 3M®, 1000BULBS.COM®, Advantium®, Aeroseal®, Alternative Energy Store®, Andersen® Windows, Atrium®, AttiCat®, Barricade®, BASF®, Berry Plastics™ Corporation, Bieber®, BioBased Insulation®, Bosch®, Building Performance Institute®, Carrier®, CertainTeed®, CMC Energy Services®, Cooper® Lighting, Corbond®, Cree Lighting®, DAP®, Demilec®, Dow®, DrainWrap™, DSIRE™, Duck® Products, DuPont™, Earthtronics®, EcoAction®, Elica®, Energy Star®, eW™, FastenMaster®, Feelux®, Fiberweb®, Fibrex®, Fisher & Paykel®, Florida Solar Energy Center®, Foametix®, Focus Lighting®, Freon®, Frost King®, Galvalume®, GE® Monogram®, GE® Profile™, Gore-Tex®, Great Stuff™, GreenGuard®, GreenHomes® America, Halo®, Hardcast®, HeadLok®, Heat Mirror™, Home Slicker®, HomeWrap®, Honeywell®, Hunter®, Icynene®, Ikea®, Ilumisys®, Ingo Maurer®, Integrity® Windows and Doors, Intel®, International Residential Code®, Internorm®, Jeld-Wen®, Journée Lighting®, Juno®, Kalco®, Kichler®, Kill A Watt™, KitchenAid®, LG SteamDishwasher™, LightFair®, Lightolier®, Lightolier® Calculite™, LiteTronics®, LiteTronics MicroBrite™, Loewen®, Lucifer® Lighting, MaxLite™, Maytag®’s Ice20®, M-D® Building Products, Milgard®, Mortairvent®, National Association of Training Excellence®, Neat® Glass, Nexamp™, Nexxus™, OlyLog®, Optiwin®, OSRAM® Sylvania®, Owens Corning®, Pactive®, Passive House®, Pella®, Pemko Manufacturing®, Phantom™, Philips®, Pilkington® Activ™, PinkWrap®, Progress Lighting®, Progress Lighting Everlume™ Series, Puron®, Raindrop®, RCD Corporation®, Renewal By Andersen®, RESNET®, ReVision Energy®, Roxul®, R-Wrap®, Serious Windows®, Solahart®, Speed Square®, StuccoWrap®, SunClean®, Superstor®, TerraLogos®, The Basic Source®, The Home Depot®, The Home Energy Saver™, Thermafiber®, Therma-Stor®, Thermotech®, Tiger Foam®, Touch ‘n Seal®, Toyota® Prius®, Tresco International®, TurboChef®, Typar®, Tyvek®, Urethane Soy Systems®, Versi-Foam®, VU1®,Weathermate™ Plus, Weather Shield®, Weather Trek®, Whirlpool®, White-Rodgers®, Wind-lock®, York® Affinity™
About Your Safety: Homebuilding is inherently dangerous. From accidents with power tools to falls from ladders, scaffolds, and roofs, builders risk serious injury and even death. We try to promote safe work habits through our articles. But what is safe for one person under certain circumstances may not be safe for you under different circumstances. So don’t try anything you learn about here (or elsewhere) unless you’re certain that it is safe for you. Please be careful. Except for new page numbers that reflect the organization of this collection, these articles appear just as they did when they were originally published. You may find that some information about manufacturers or products is no longer up to date. Similarly, building methods change and building codes vary by region and are constantly evolving, so please check with your local building department.
Special thanks to the authors, editors, art directors, copy editors, and other staff members of Fine Homebuilding who contributed to the development of the chapters in this book.
Contents
Introduction
3
part 1 : ENERGY EFFICIENCY Every House Needs an Energy Audit
4
Home Remedies for Energy Nosebleeds
12
Can a Vintage Home Be Energy Efficient?
20
Efficient Houses Need Fresh Air
30
A Practical Look at Deep-Energy Retrofits
39
Part 2: INSULATION Upgrade Your Attic Insulation
46
Beef Up Your Old Insulation without Tearing into Walls
56
All You Need to Know about Spray Foam
65
Making Sense of Housewraps
70
Using Rigid Foam for an Efficient and Dry House
79
Basement Insulation Retrofits
82
Weatherstripping
85
Part 3: WINDOWS A Buyer’s Guide to Windows
91
Do Europeans Really Make the Best Windows?
104
Installing Replacement Windows
110
Part 4: HEATING AND COOLING Is Your Heating System an Energy Beast?
118
Finding the Sweet Spot: Siting a Home for Energy Efficiency
128
Cool Design for a Comfortable Home
136
Central Air-Conditioning: Bigger Isn’t Better
145
Part 5: LIGHTING and appliances Low-Energy Lighting, High-Energy Design
151
The Bright Future of Lighting
159
The Energy-Smart Kitchen
165
Solar Hot Water
174
Energy-Saving Thermostats
182
Credits
185
Index
186
in t r od u c t ion
I
f there is one topic that has dominated the homebuilding field in recent years, it’s energy efficiency. But for all the headlines and airtime dedicated to the topic of
trimming home-energy use, many of the discussions they generate don’t go any further than the admission that, yes, we need to work harder to save energy where we live. What we really need to talk about is how. At Fine Homebuilding magazine, we focus not only on what good, responsible builders should do to construct or remodel homes that don’t waste energy, but also on how they do it. This book explains how you can, too. In The Energy-Smart House, you’ll be able to follow these builders step-by-step through critical energy enhancements that include air-sealing, insulation upgrades, and window replacement, as well as choosing the best low-energy fixtures and appliances. Today, the opportunities for reducing the energy requirements of the homes we live in—no matter how old they may be—are tremendous. The evolution in building products alone, from housewraps to LED lighting to high-performance windows, has equipped builders with a wide array of options to make homes more durable and healthier as well as less costly to live in and maintain. Ever-advancing technologies enable new mechanical systems to deliver heating, cooling, and hot water more effectively and at a lower cost. All the while, a greater understanding of building science enables knowledgeable builders to craft efficient, long-lasting dwellings regardless of the climate in which they build. The fact is, true energy efficiency can only be achieved through a multifaceted approach that takes the whole house, its site, structure, and systems, into account.
A home is not made “energy efficient” by popping in a few new windows or loading up the attic with cellulose. Good builders know the path to energy efficiency is a multistep process, and that each improvement influences the steps that follow. And that the conscientious application of smart building techniques like the ones found here is the most reliable roadmap they can follow in their pursuit of an energy-smart home.
Debra Judge Silber, Managing editor, Fine Homebuilding magazine
3
energy efficiency
1
Every House Needs an Energy Audit By Jefferson Kolle
I
n the bill from her gas company, Leslie
audits. And while an old leaky house might
MacKensie of Minneapolis learned that
be the obvious choice for an energy-waste
she could have a free energy audit performed
diagnosis, new houses can benefit, too. The
on her house, so she made an appointment.
results can be an excellent marketing tool
After assessing the 1915 bungalow, the audi-
for builders and can help homebuyers
tors showed her air leaks and other problems
qualify for an energy-efficient mortgage,
that resulted in a monthly bill of $110. The
which uses energy-cost savings to lower
auditors left her with weatherstripping and
debt-to-income ratios.
foam-insulation pads to install, along with a list of other needed improvements.
The most important thing to note about energy audits, however, is that they don’t
Chipping away at the list has had dramat-
save money or energy. Implementing the
ic results. Even after she expanded her home
recommended improvements is how the
with a small addition, her current gas bill
savings happen.
averages only $80 a month. “Almost as important,” she says, “is that now our home is really comfortable to live in all year round.” Home-energy auditing—the process of diagnosing and recommending improvements to reduce a house’s energy consumption—is not a new idea, but the reasons to get an audit are more pressing as concerns about costs, comfort, personal health, and the environment loom large. Along with free or reduced-cost audits offered by utility companies, an increasing number of private companies perform
There Are Two Types of Audits Energy audits vary in complexity from an unscientific but learned assessment to one that uses an assortment of diagnostic equipment to measure the performance of a house and its systems. The unscientific assessment typically consists of a thorough two- to three-hour walk-through, during which the auditor makes a visual inspection; takes photographs; and records information about the
Locating leaks. One of the most valuable scientific tools an auditor can use is a blower door, which is mounted temporarily on an exterior-door frame. The blower door’s calibrated fan pulls air through the building, measuring the amount of air leaks. While the fan is operating, an auditor uses a smoke stick to locate the leaks. Smoke pulls away from the leaky spot and toward the blower door. Ever y House Needs an Energy Audit
5
Most experts agree that air
size of the building and specifics about the
easily equate to leaving the bottom sash of a
assumed efficiencies of the insulation, the
double-hung window open all year long.
appliances, and the HVAC (heating, ventila-
To pinpoint where air infiltration is hap-
tion, and air-conditioning) system. (For in-
pening, the auditor holds a smoke stick or
infiltration is the
stance, he might know how fiberglass batts
smoke pen in front of doors, windows, or
No. 1 cause of
should be performing but can’t tell if they
other suspect areas (see the inset photo on
were installed properly.)
p. 5). The pen emits a chemical smoke that
energy loss in any house.
The scientific approach, which takes four to six hours to complete, uses diagnostic
fan to identify air infiltration. The auditor
equipment to record and quantify a home’s
makes a note of the location and later sug-
energy shortcomings. The auditor completes
gests how to seal the leak.
a walk-through of the house, but he doesn’t stop there. The first step is often a blower-door test.
6
Energy Ef ficiency
A blower-door test can find air leaks in heating and cooling ductwork that runs through unconditioned spaces, such as an
After closing windows, exterior doors, and
attic or a crawlspace. But it can’t find leaks
often flues, the auditor turns on a calibrated
in ducts that run through the conditioned
fan mounted in an airtight frame temporar-
space, such as walls and floors. A tool
ily set in an exterior door (see the photo on
made specifically for that job is a calibrated
p. 5). The fan reduces air pressure inside the
airflow-measurement device called a duct
building, pulling air in through all the holes
blaster. After turning off the blower door
in the building envelope. Depending on the
and taping over the floor, wall, and ceiling
blower door’s supporting software, the audi-
registers, the auditor connects the blaster to
tor quantifies the number of air changes the
a central return in the system and measures
house goes through in an hour (expressed as
its airtightness. Leaky ductwork can lead to
ACH) as well as the combined size of all the
substantial energy loss, which can be espe-
air leaks. In an old house, those leaks can Making the improvements. Sealing leaky windows and air ducts, and adding insulation are the most common improvements auditors suggest. Attics can be the largest culprits for air and energy loss.
wafts away from the leak and toward the
cially costly when that loss is happening in
Infrared imaging paints an informative picture. Auditors can use a thermographer, or infrared camera, to locate differences in the temperatures of a house’s parts. The image in the handheld infrared camera shows cold spots in blue around the warmer crown molding, indicating insulation voids. In the inset photo, taken outside in the winter, heat loss from inside the house appears in red and yellow. Cooler areas of the exterior wall appear blue. An auditor will use images like this to indicate un- or under-insulated areas, air leaks, and even moisture problems.
an unconditioned space. Perhaps the best qualitative scientific tool an inspector pulls out during a diagnostic audit is an infrared thermograph, a camerastyle device that shows the relative temperatures of objects portrayed as a kaleidoscopic image (see the photos at right). The colors reveal heat loss or gain, which indicates if a wall or attic floor is insulated, for example, and how well that insulation is performing. It also can identify moisture problems and leaky pipes behind the walls. The auditor might also use a combustion analyzer and flue-gas monitor to measure the efficiency of boilers and furnaces (see the left photo on p. 8). Finally, he plugs in an electricity-usage monitor near appliances like the refrigerator to determine their efficiency. Proponents of these diagnostic audits say that scientific measuring allows individual house components to be assessed as part of a whole system in which change to one part affects another. For instance, extensive airsealing could make the building too tight and result in a furnace’s flue gases being sucked down a chimney and into the living space—something that might not be detected without testing. This system’s approach might also show that increasing insulation levels would allow a home to be heated by a smaller boiler. Test equipment can measure these kinds of occurrences, whereas a strictly visual inspection results only in an educated guess. The other main reason to use testing equipment is that retesting can determine the success of the recommended improvements. Steve Luxton, regional manager for CMC Energy Services® (www.cmcenergy.com), disagrees with the need for scientific test-
says Luxton. “[They] don’t need a fan to tell
ing. Luxton’s company has trained more
you where the leaks are.”
than 1,000 energy auditors, 90% of whom
His point is well taken; most experts agree
are working as home inspectors, the folks
that air infiltration is the No. 1 cause of en-
that mortgage companies require you to hire
ergy loss in any house. Most buildings have
before they’ll lend you money. “These guys
common air-infiltration areas that are easy
already know what to look for in a house,”
to spot if you know where to look.
Ever y House Needs an Energy Audit
7
A duct blaster is not quackery. Similar to a blower door, a duct blaster is a calibrated fan. It is used on buildings with forced-air heat or central air-conditioning. Leaking ducts can decrease the overall efficiency of your heating and cooling system by as much as 20%.
course of a year. A home that scores 100 is built to the energy specs of the 2006 International Residential Code® (IRC). Once the house is completed, it is tested by a RESNET auditor using scientific testing equipment to ensure the as-built house conforms to the as-planned HERS rating. The reasons to get a verified new-house Tools for a furnace tune-up. Your heating and airconditioning systems could be the third-largest energywasting devices in your home. An auditor can use a combustion analyzer and flue-gas monitor to measure the efficiencies of your systems.
HERS rating are fourfold. Not only can a HERS-index rating help homeowners to
New Homes Need Audits, Too
qualify for an energy-efficient mortgage, but
There are a number of reasons to have a new
third party. The HERS rating is also an excel-
home audited as well, not the least of which is to ensure that the building envelope and mechanical systems are performing as they
lent marketing tool, and it helps builders to qualify in the Energy Star® program.
natresnet.org), a not-for-profit membership corporation, has developed an index
As home-energy audits become a more
called the home-energy rating system, or
important part of building and owning a
HERS, that both predicts and confirms a
home, more and more auditors are enter-
new home’s energy performance. The HERS
ing the field. Free audits are available from
index can be used to evaluate a home’s plans
local utility companies, but this avenue has
and specifications before it is built, then as-
its pros and cons (see the sidebar on the
sign it a number from 0 to 100. A house that
facing page). Independent auditors tend to
scores a 0 is said to be “net zero,” meaning it
offer various packages that can be tailored to
produces as much energy as it uses over the
your home’s needs and your goals. Look for
Energy Services Network (RESNET®; www.
Energy Ef ficiency
cies have been verified by an independent
How to Hire a Qualified Auditor
were designed to perform. The Residential
8
it also assures them that building efficien-
an auditor who has been certified by CMC
involved, which there often is. Affiliates are
Energy Services, Building Performance Insti-
allowed to set their own prices for training,
tute®
so they vary across the country. A searchable
(BPI; www.bpi.org), or RESNET.
Although they don’t provide diagnostic
database of all BPI-certified professionals is
testing of a home, CMC Energy Services
maintained on the Building Performance
auditors are screened and complete energy-
Institute’s website.
inspector training. CMC-trained auditors
RESNET has a similar teacher-mentor
pay $300 and spend two classroom days
system. RESNET trains providers, who then
learning about energy fundamentals; they
train raters, who are the folks that do the
also receive instruction in how to use the
audits. Certification requires a week of class-
company’s proprietary reporting software.
room time, and the cost varies from $1,200
Online refresher courses keep inspectors up
to $1,500, depending on the provider. A list
to date. CMC maintains a searchable data-
of providers and raters is available on the
base so that you can find an inspector in
RESNET website.
your area. BPI in Malta, N.Y., trains auditors to use
The Department of Energy’s Energy Star program is not involved directly in the certi-
diagnostic-testing equipment. To get BPI
fication of auditors, but Energy Star endorses
accreditation, an auditor goes through “a
both RESNET and BPI auditors in two sepa-
rigorous, credible, and defensible written-
rate programs. In the first program, Energy
and field-examination process administered
Star Qualified New Homes, houses must score
to individuals by BPI or its affiliates,”
at least an 85 on RESNET’s HERS-index
according to BPI’s website. BPI affiliates,
rating. The second program, Home Perfor-
such as the Metropolitan Energy Center
mance with Energy Star, currently has locally
in Kansas City, Mo., are trained to give
sponsored programs in 28 states that help
exams to prospective auditors. Then BPI
homeowners to improve a home’s energy ef-
awards certification to those auditors who
ficiency cost-effectively. The contractors that
pass the tests.
participate in the program are BPI-certified
According to Dustin Jensen, associate executive director at Metropolitan Energy
and are listed at www.energystar.gov. Regardless of certifications, ask any audi-
Center, a 40-hour auditor-training class costs
tor you might hire for a list of customers
$1,000, and the examination costs about
that you can contact to find out if they were
$500, if there is no government subsidy
satisfied with the auditor’s work.
Don’t Give Free Audits the Cold Shoulder
P
resident Jimmy Carter’s 1977 Energy Policy Act required utility companies to provide energy audits to their customers. These programs have helped hundreds of thousands of homeowners to tune up their houses. One advantage of many utilitycompany audits is that they might also give you some free products, such as compact-fluorescent lightbulbs, or perform remedial work, such as air-sealing and weatherstripping. Although it might seem contrary, utility companies want homes to save energy. It helps them to manage
peak power loads, the times of day or season when energy use is at its greatest. Plus, it’s not bad for a company’s public relations. And an electric company can actually save money if it doesn’t have to construct new power plants. Don’t be surprised if a so-called free audit comes with strings attached, though. An electrical utility in Connecticut, for example, has a greatsounding program. But for the program to be free, the house must be heated with gas or electricity; otherwise, the service costs $300.
Ever y House Needs an Energy Audit
9
Consultant or Contractor?
ica, a Syracuse, N.Y., firm that tests homes
There are two schools of thought about
and then does improvement work, disagrees.
whom to hire to perform a home-energy
“Would you take your car to one guy to tell
audit. One says that a disinterested third party
you what’s wrong with it and then to an-
is the most trustworthy opinion, while the
other to do the repairs?” he asks. Some com-
other argues for the convenience of hiring
panies, including GreenHomes, even have a
someone who can pinpoint the improve-
financing program for energy-performance
ments needed and then perform the work.
upgrades.
Brian Smith of Energy Saving Comfort
Mike Rogers, senior vice president of business development for GreenHomes® Amer-
thing other than testing services. When he
Costs and Reports Vary
sits down with customers to review what his
Whether a basic inspection or an in-depth
blower door and infrared camera have detect-
scientific test, an auditor’s findings will
ed, they know that “I’m not then going to
likely be output from software that not only
try to sell them new windows or a furnace.”
takes into account the physical data about
CMC’s Luxton concurs: “We feel strongly
the structure but also data about utility bills,
that an audit should be performed by an
the local climate, and, possibly, comparative
unbiased person.”
information from other houses.
Systems (www.escs1.com) prides himself on the fact that his company isn’t selling any-
John Jennings is an energy auditor with
A CMC-trained auditor will generate a
Steven Winter Associates, an architecture/
report about the existing house’s needed im-
engineering research and consulting firm in
provements, including a cost-benefit analy-
Norwalk, Conn. He favors the idea of inde-
sis and payback time in years. CMC doesn’t
pendent auditors who can provide a list of
control what its inspectors charge, but
vetted contractors that can make the recom-
Luxton says audits cost from $200 to $400,
mended improvements.
depending on the size of the house. RESNET auditors are licensed to use com-
Online audits can help you save, too. Spend some time with online home energy-savings applications, and you could realize substantial savings on your energy bills (see the sidebar on the facing page).
pany software that produces a HERS-index report. An audit with a HERS report (report fees can run around $150) costs from $1,000 to $1,500. While BPI doesn’t supply its own software, there are independent programs available that auditors can choose. An audit from BPI-accredited TerraLogos® in Baltimore costs $495, and though it is thorough in its assessment of and recommendations for the house’s existing systems, it does not predict energy savings if the suggested upgrades are carried out. On the other end of the scale is a soupto-nuts audit done by a company such as Steven Winter Associates. Along with a basic inspection of a house up to 4,000 sq. ft., which includes no scientific testing, the a-la-carte audit menu could include a blower-door test, a duct-leakage test,
10
Energy Ef ficiency
DIY Online Audits
B
efore you schedule an audit, you might want to check out the many online do-it-yourself energy-audit programs. Although they don’t require any scientific testing equipment and some suggest lots of behavior modifications—turn down your thermostat, take shorter showers—their computer applications will give you guidance and information about energy improvements. According to Energy Star’s John Passe, “A homeowner who follows
these programs to a T might save 20% to 30% on his energy bills.” Along with your local utilities, here are some sites to try. Home Performance with Energy Star, the branch of the organization that deals with existing homes, has three auditing tools you can complete online at www.energystar.gov. After entering data about your utility bills, the Home Energy Yardstick gives you a 1 to 10 rating on your consumption as compared to others in
your area. The Energy Star Home Advisor gives you savings recommendations based on your ZIP code and utility use. Energy Star at Home offers room-by-room and lifestyle energysaving tips. The Home Energy Saver™ (http://hes.lbl .gov), developed by Lawrence Berkeley National Laboratory, is sponsored by several government agencies and is visited by about 750,000 people a year. To start, all you do is enter your ZIP code;
appliance-combustion testing, infrared-
public comment, the new standard is
imaging, energy-modeling, and a HERS rat-
intended to clear up confusion among
ing. All this adds up to an audit that costs
homeowners, but the reciprocity between
upward of $2,000.
the two organizations will also help audi-
hours later, you will have gathered tons of valuable information. The Alliance to Save Energy, a nonprofit funded by private grants and government agencies, sponsors Home Energy Checkup (www.ase.org). According to the site, you can select from more than a dozen energyefficiency measures, see how much money and pollution you can save, find out where to get energy-efficient products, and pick up tips on how to act on your choices.
tors, many of whom have previously felt the
What’s Next for Energy Audits
need to get accreditation from both non-
The business of energy-auditing is getting
will recognize the efficacy of all types of
huge. “It’s at a tipping point,” says Courtney Moriarta, senior engineer at Steven Winter Associates. “Not only do homeowners think it’s a cool thing to do, but it’s also being driven more and more by energy-efficient mortgages and potential tax credits.” Both Massachusetts and California are working
profit groups. Steve Baden, executive director of RESNET, says that the standard energy audits and auditors from “the DIY type to the guy with the clipboard and flashlight to the guy who also uses a blower door and an infrared camera.” Jefferson Kolle is a former editor at Fine Homebuilding.
on legislation that will require house sellers to divulge energy-audit information to prospective buyers. Also on the horizon is a joint energyauditing standard between RESNET and BPI (which could be adopted by Energy Star, too). Currently in draft form and open to Ever y House Needs an Energy Audit
11
energy efficiency
1
Home Remedies for Energy Nosebleeds By Bruce Harley
M
didn’t have to be pretty. Now, not taking the
Gaps in the Construction Sequence Cause Many Problems
time to smooth out a mortar joint that no
People think windows and doors are the big-
one will see may not rank as a great offense.
gest leaks in a house because windows and
But the fact is, many things that go wrong
doors are the most visible holes. But even
in home building go wrong where sloppy
old windows and doors are relatively small
work is done because “it’s not going to show,
holes. In reality, the majority of energy leaks
so it doesn’t matter.” I know this because as
happen in places you can’t see, where one
an energy consultant, I plug the same nose-
subcontractor’s work ends and another’s
bleeds in new and old homes alike. We’re
begins: behind the drywall, up in the attic,
good at cutting construction costs but bad at
or down in the crawlspace. Even when each
building houses that serve their owners well,
trade does its job well, problems can occur
minimize operating costs, and also reduce
because nobody sees the big picture. The
pollution.
way the work fits together is as significant as
y friend Terry Brennan told me that on his first job as a mason’s tender
he learned two things: “Whatever I did was wrong,” and “If the work wasn’t going to show, don’t strike the joints” because it
the work itself. The gaps between subs’ responsibilities usually translate into gaps in a house’s thermal boundary. These gaps are addressed in current building codes, but building inspec-
tors can’t always offer protection. Sometimes
joist cavity or, better yet, insulate under the
they don’t understand; sometimes they just
roof deck (see p. 16).
don’t enforce energy codes. The architect,
Rim joists also have multiple holes cut
the general contractor, or the homeowner
in them for dryer vents and outdoor water
must take the responsibility for understand-
faucets. Rim joists are best sealed when the
ing and closing these gaps.
house is built. The top and bottom edges
Amazingly, the two trades most concerned
should be sealed with construction adhesive
with energy efficiency—HVAC (heating, ven-
during framing and insulated with spray
tilation, air-conditioning) and insulation—
foam afterward.
rarely follow the minimum industry standards for their work. The reasons differ, but they share one common element: Their work is hidden behind drywall. The only feedback they get is when these systems fail, when our homes are uncomfortable (an issue that’s often misdiagnosed) and high energy bills mount. Pressure to keep upfront costs low and underestimating the magnitude of these problems are also common to both trades. This standard of care isn’t reasonable. Just because it has always
Architectural Massing Can Often Mean Massive Leaking Architects use features such as cantilevers and wraparound porches to break up the massing of a mundane facade. I have nothing against great-looking houses, but these architecturally interesting details can create giant energy nosebleeds.
been done this way doesn’t make it right.
Some Holes Are So Big That Nobody Notices Them It’s not only insulation and HVAC contractors who are inadvertently sabotaging our houses. Framers often construct large holes that extend from the basement to the attic in the form of chimney, plumbing, and duct chases. These chases are hidden behind drywall or are covered by fiberglass-batt insulation. But insulation alone won’t prevent conditioned interior air from escaping. Big holes should be sealed with plywood, rigid foam, or drywall and caulk or spray foam. Kneewalls and rim joists are two more often-missed examples. Think of them as long holes in a house. Kneewalls are the short walls found in finished attics and in bonus rooms above the garage. Insulation is usually put in the kneewall and under the floorboards, but this insulation doesn’t keep a room warm unless you block each Home Remedies for Energy Nosebleeds
13
Insulation and air-barrier details are often missed in cantilevered areas. The underside of a cantilever should be covered with solid
Uncover the Hidden Holes in Your House
sheathing (caulked in place) before finish materials are installed. Roof and wall sheathing is frequently left off below intersecting porch and garage roofs. The spaces below these roofs often connect to vented attics; they are just big air vents to the outdoors. Fancy details like tray ceilings and curved walls also can create big holes that open to attics. Great-looking houses should also perform well. Architects should draw a line between inside and out on the blueprints, and make sure the house is built that way.
With Insulation, a Little Laziness Goes a Long Way People naturally think that if you cover 98% of a surface with insulation, you’ll get 98% of the performance. This thinking is horribly wrong. Gaps and missing insulation create a hugely disproportionate performance pen-
TWO BIG HOLES CAN COST YOU MONEY. Directly above a bathroom, this attic view reveals a dropped soffit and a large plumbing chase for the vent stack. The soffit connects the attic with the walls; the plumbing chase is a direct hole running through the house. These two leaks are like leaving a window open. The Fix: Cover the open framing with rigid foam or plywood, and seal small openings with spray foam. Finally, cover them with insulation. Loose-fill insulation such as cellulose is cheap and easy to install.
alty. If you install R-38 batts in an attic but leave 0.5% of the surface area uncovered, you end up with R-32 (16% reduction in R-value). Leave 2% uncovered, and you drop to R-22 (42% reduction). So with 98% coverage, you get 58% of the performance. If you run across information saying it’s not cost-effective to add insulation, it probably assumes the initial R-value is what you say it is. In all likelihood, the R-value is less than half what you think, and the upgrade is worth much more—provided it’s done right.
14
Energy Ef ficiency
This dropped soffit connects the walls to the ceiling, making a path for air leakage.
When framing lumber shrinks, the gap between top plates and drywall can add up to a 5-sq.-ft. hole.
Balloon-framed rake (gable-end) walls create a series of large holes into the attic; they should be sealed.
Remember to seal all joints.
The clearance around this chimney is big enough to serve as a chase for heating ducts.
Heat from recessed lights drives air into the attic faster than the air would move on its own.
Wiring holes in top plates allow air to leak into the attic.
SOME HOLES ARE HIDDEN BEHIND DUCT TAPE. Poorly sealed ducts lose up to 40% of the air they transport. If they’re in the attic, this can cause ice dams in winter. In the summer, it wastes money. The Fix: Instead of relying on duct tape, seal joints with RCD Corporation®’s latex duct mastic ($20/gal. at www.efi.org). To apply, wear two pairs of gloves (cotton over vinyl). Bridge gaps larger than 1⁄4 in. with fiberglass tape, followed by mastic.
SOME HOLES ARE CODE-REQUIRED. Extending from basement to attic, code-required chimney-clearance space (see the photo at left) can be a major escape route for conditioned air. If the clearance is supersized to accommodate ductwork, then the losses multiply. The Fix: The code also requires noncombustible fire-stops; close off the opening with sheet metal or cementboard and fire-rated sealant (available at most hardware stores and home centers).
Cut sheet metal or cementboard to bridge the gap between the framing and the chimney. Seal the gaps with a fire-rated sealant.
Home Remedies for Energy Nosebleeds
15
Where cold air is supposed to go...
Kneewall ...Where cold air really goes
Solid blocking can stop cold air.
Kneewalls and vented roofs mean cold bonus rooms. insulation can’t stop chilly air. consider the size of this leak: each joist bay (the space between joists) is roughly a square foot times the number of joist bays, twice. for a 40-ft.long cape, this amounts to a 57-sq.-ft. hole in the thermal boundary that nobody notices. The Fix: Two options work. use solid blocking (foam board or plywood) in each joist bay (seal the edges with canned foam), or insulate the roof with spray foam.
Putting an HVAC system in the attic is like putting it outside. in the winter, uninsulated attics are almost as cold as the outdoors; in the summer, they’re much hotter. if r-30 insulation is required in the attic floor, does r-6 make sense for the air handler and ducts? no. The Fix: Move the HVac out of the attic, or insulate the attic at the roof. Spray foam is a good choice. calculating the correct size (see above) and optimizing duct layout make it easier to find room within the home’s conditioned space.
16
This air conditioner is in the hottest part of the house.
HVAC Ducts Can Putting the Air Leak One-Third of the Handler Outside Air They Transport the House Is Not From 20% to 40% of the air that comes out a Good Idea of furnaces and air conditioners never gets to the rooms it’s supposed to heat or cool. When you consider that most of the ducts are in attics, garages, and vented crawlspaces, the effect of that loss is huge: We’re heating and cooling the outdoors. Sometimes whole rooms are disconnected, as when the ductwork isn’t connected to the register and the duct spews conditioned air into the attic or crawlspace. Return ducts often leak more than supply ducts; although they cause less energy loss, these leaks lead to moisture problems and pressure imbalances that pose health and durability risks by contributing to mold, ice dams, and even carbonmonoxide poisoning. Required by code, duct-sealing is rarely completed and even more rarely tested. Houses more than 10 years old didn’t have this code requirement. Every connection in every duct run should be sealed with mastic (not tape), and the system should be pressure-tested, just like your plumbing. Holes in the air handler can be sealed with aluminum-foil tape because mastic would render the cabinet unserviceable. After you seal the ducts and the cabinet, insulate them carefully.
Many air handlers and ducts are in attics. This location is a lot more costly than people realize. Putting an air handler and ductwork in the attic, garage, or crawlspace is like putting it outside the house. In winter, attics are almost as cold as the outdoors; in the summer, attics are much hotter than the outside temperature. If you must place the air handler and ductwork in the attic, you can do a few things to minimize energy losses: Seal everything with mastic; insulate the air handler carefully; and keep the ducts low and covered with blown insulation. Even better, use spray foam on the whole roof and gable ends so that the attic space is within the house’s thermal envelope. The best idea, though, is to run the mechanical system inside the house. You can use smaller mechanical equipment with smaller ducts in shorter runs; it’s easier to design space for them within the house. The payoff is a much more efficient HVAC system that increases comfort while decreasing operating costs. For more information, go to www.toolbase.org/Design-ConstructionGuides/HVAC/forced-air-system.
Retrofits can be more difficult. If you can access the ducts, you can use mastic under the insulation (put the insulation back when you’re done). If the ducts are inaccessible, they can be sealed from the inside with a product like Aeroseal® (see www.aeroseal .com for local contractors), or you can move the insulation and the air barrier to bring the ducts inside the thermal boundary.
Home Remedies for Energy Nosebleeds
17
How Durable Is Spray Foam?
This uncovered cantilever is somewhat unusual, but finished overhangs are often covered only with vinyl soffit.
Cantilevers can be like open windows. The same principle applies to cantilevers as to kneewalls: cold air has a direct path to the living space through the insulation and floor framing. The Fix: cover the underside with solid sheathing, caulked in place.
Q: Spray foam is touted as a “superior” insulation material. I’ve been building for nearly 20 years, however, and I’ve occasionally found spray foam that has settled in the wall cavity and/or disintegrated enough to lose all its effectiveness. How do we know today’s spray foams won’t do the same thing in 30 years? —Mike Connors, Beacon, N.Y. A: The failed foam you’re describing is likely urea-formaldehyde foam insulation (UFFI). It was installed in many homes in the 1970s, but eventually was banned in Canada and the United States due to concerns about chemical off-gassing. UFFI also tended to become brittle, shrink, and crumble over time, affecting durability and performance. The current generation of spray-polyurethane foams is based on a different chemistry, so the cured foam is much more stable. This quality suggests that spray-polyurethane foams will last much longer than UFFI and will retain their flexibility and mechanical integrity. I wouldn’t worry about the durability of the foams that are currently available. In fact, I believe that in some applications today’s spray foams add to the durability of the overall structure by reducing air leakage and vapor diffusion. —Bruce Harley
Oversize AC Units Can Hide Many Big Problems Oversize air-conditioning systems are the norm, not the exception. It’s easier to pick
18
Energy Ef ficiency
of the problems I’ve discussed here. Poor insulation, duct leaks, and more can be covered up by blasting twice as much cold air through the ductwork as would be necessary if things were done correctly. If you double the size of the AC unit, you
a huge system based on erroneous rules of
can lose 50% of the performance and still
thumb than to spend time designing a more
provide enough comfort so that the home-
suitable but smaller system. Oversize systems
owner won’t call you back. But a behemoth
have the added problem of masking many
AC unit short-cycles (turns on and off too
Oversize HVAC Is Overkill
W
hen it comes to air-conditioning units, oversize air handlers waste energy, burn out faster, and leave the house cold and clammy. Unfortunately, many HVAC contractors still rely on rules of thumb to determine system size. The best way to get the right-size HVAC unit is to model your home’s energy features with one of the many software programs available (such as the one at www.hvaccomputer.com; $49 for homeowner version). To calculate whether an existing AC unit is too big, measure the number of minutes per hour that the AC unit runs on the hottest afternoons in the summer. Then divide 60 by the number of minutes to determine the amount that the unit is oversize. For example, 60 ÷ 30 = 2× oversize; 60 ÷ 20 = 3× oversize.
quickly), which hurts its energy efficiency,
the windows at the design stage to at least
degrades its ability to dehumidify the air,
Energy Star (preferably beyond) is a lot less
and shortens its life. A larger unit is also
expensive than buying substandard win-
noisier and costs more to install (both sys-
dows now and replacing them later. Even
tem and ducts). The solution is simple: Pay
so, windows are not usually the first place
for the load calculations, and size the unit
to start looking for big savings, because the
correctly. In fact, according to the Air Con-
other nosebleeds are running hard.
ditioning Contractors of America (ACCA), it’s often better to undersize an AC system a little bit.
Bruce Harley is technical director of Conservation Services Group (www.csgrp.com) in Westborough, Mass.
Water Heaters and Windows Are the Next Savings Opportunities Water heaters store hot water all day long. They keep it hot on the off chance that you’ll need it. Tankless, or on-demand, water heaters, on the other hand, convert cold water into hot water when you turn on the tap. You’ll notice that windows aren’t on this list. Only after you correct all the things I’ve mentioned will your windows start to look bad. If you’re building a home, upgrading
Home Remedies for Energy Nosebleeds
19
energy efficiency
1
Can a Vintage Home Be Energy Efficient? by betSy pettit
I
n America, there are around 58 million
process because many of them have under-
houses that were built before the last
gone numerous renovations over the years.
energy crisis. Because these pre-1970s houses
You never know exactly what you’ll find.
have little or no insulation, they are all ripe for energy-efficiency improvements. Houses eat up 20% of the energy used in this country and account for 21% of the carbon dioxide that contributes to global warming. This adds up to a huge opportunity. America’s old houses can be made much
In Old Houses, Most Systems Are at the End of Their Useful Life
tighter and can even approach net-zero
A hundred years can take its toll on infra-
energy use. Here, I’ll highlight three houses
structure, and this is often the case with old
that my company, Building Science Corp.,
houses. The water line from the street, electri-
has renovated. Each house had different
cal wiring, plumbing, mechanical systems—
limitations and learning curves. I share one
all are often nearing the end of their life. It
of the houses with my husband and business
would be foolish to renovate a house with-
partner, Joe Lstiburek, and two of them have
out replacing these basic systems. Windows
been used as our office space.
often no longer function as intended, either.
Renovating an old house is an expensive
Their ventilation properties are hindered by
process. It’s also a delicate process because
layers of paint, or they simply became swol-
the end product must retain its charm. Most
len shut years ago. If neglected, siding can
old houses are still around because people
need repair or replacement, too.
love their timeless form, floor plan, trim, de-
While the shape, floor plan, and details
tails, and historical significance. Renovating
of an old house allow it to endure, people
an old house is a surprising and challenging
often think they need an addition to provide
another bathroom, bedroom, office, or better views. Then they spend money building an addition, only to spend all their time in this new space because the rest of the house is uncomfortable. They don’t really get more space in this deal; they get a smaller space that’s comfortable.
A Tricky Victorian
Our First Renovation
Energy Upgrades Are Cheaper Than You Think While the cost of fixing wet basements and adding bathrooms can add up quickly, energy upgrades can be folded in without putting projects out of reach. In fact, they don’t really cost that much more because they’re integral to the decisions and choices made in the renovation process. If you consider your renovation from a whole-house approach, you might find that you can add modern conveniences (an extra bathroom, bedroom, or office space) and comfort without building an addition, and
third time is a charm
basement and attic, you often can reconfig-
Case Studies Illustrate Real-World Challenges
ure the floor plan to accommodate an extra
The three homes featured in this chapter
bathroom, a larger kitchen, or a master suite.
have several things in common. First, they
Replacing the furnace, the boiler, or the
are all more than 90 years old. Two of them
reduce energy costs in the process. The basement and attic are already built; you just need to use them. By adding rooms in the
HVAC system might cost $10,000 before you
were built in 1860 and the third in 1916.
are done. But the upgrade could easily save
Second, they all had their major systems
$1,000 a year in heating and cooling costs.
totally replaced: new wiring, light fixtures,
Even in simple payback terms, this new
plumbing, and mechanical systems, includ-
system would pay for itself after 10 years.
ing the addition of central air-conditioning.
Amortized into a 30-year mortgage, it costs
Third, they all had attic spaces that were
$27 per month; the savings works out to
incorporated into the living space of the
$83 per month for a net gain of $56 per
house by moving the insulation from over
month. Because we know energy costs are
the second-floor ceiling to under the roof.
rising, these numbers will only get better.
Fourth, they all had insulation added under
Can a Vintage Home Be Energy Ef ficient?
21
Seven Steps to Net-Zero Energy Use
I
n renovating old homes into superefficient ones, there is a definite path to success: Start where you can get the most bang, and work your way down the list. After you get past item 5, the house will be efficient enough to downsize the mechanical equipment, which you replaced in step 1. If you’re planning to go at least through step 5, keep that in mind before buying a new boiler or HVAC unit.
dollars right away. Replacing window air conditioners, which we did in all these houses, with a central system also can save energy right away, as long as the ductwork has been placed in the conditioned space. Solar water heating is a good option to add here if you can afford it, but at the very least, upgrade the efficiency of hot-water production by coupling the tank to the boiler.
1. Upgrade the mechanical systems
2. Bring the basement and crawlspace inside the house
An old furnace or boiler is often the worst energy user in an old house. Many houses built prior to 1920 still have old coal-fired boilers that were converted to gas or oil. These units are workhorses, but use a lot of energy. A new furnace or boiler can save energy
Warm, dry basements and crawlspaces can extend living and storage space. Wet basements are the source of high humidity levels and discomfort in the summertime in old houses. They also can be the source of mold growth that gets distributed around the
If air leaks in at the bottom of the house, it leaks out at the top, which makes a house cold and drafty in winter. A poorly insulated roof also can make a house hot in summer. Airsealing is a by-product of good insulating, so it’s really a onestep process. Using spray foam under a roof also can eliminate the need for roof venting, which is tricky in complicated roofs.
4. Replace the windows With the bottom and top of the house sealed and insulated,
of energy use that ranged from 30% to more
applied to the inside of the exterior founda-
than 100%. While the renovations cost
tion wall. Fifth, they all had at least some
more than $100 per sq. ft. for each home, all
windows replaced, and all had new window
were appraised at values exceeding that cost
openings added in critical areas to provide
after the renovations were complete. Some things are different in each case,
ing to the home. Sixth, all the homes had
too. The two oldest homes had major
bathrooms and bedrooms added. Finally, we
structural issues that needed to be repaired
replaced inefficient window A/C units with
before other work could be done. Founda-
central A/C systems in each house.
tions needed to be rebuilt, and additional
Because of the work in the basements and
Energy Ef ficiency
3. Superinsulate and air-seal the roof
a new basement slab, as well as insulation
better views of the yard and better daylight-
22
house. Spray foam is a fast, effective way to bring these areas into the conditioned space while sealing the leaks between foundation and floor framing.
columns and beams were added for support.
attics, all the homes had increased living
One house, the Greek revival, had frequent
area without increasing the footprint of the
basement flooding that had to be stopped,
home. And while the living space increased
and its attached barn was leaning enough
by 30% to 100%, all of them saw a reduction
to fall down. The Victorian was in a historic
the next opportunity is the walls. Old windows are like big holes in the walls. They often leak both air and water into the house while functioning poorly. They might not open and close properly, and can be obscured with storm windows and screens that diminish the amount of light that can enter. Properly installed, Energy Star (or better) windows seal the holes in the walls to keep out water and weather extremes. (For more, see “A Buyer’s Guide to Windows” on pp. 91–103.)
5. Insulate the walls Filling empty wall cavities with cellulose is a cheap, easy, effective way to warm up an old house. Blowing cellulose into existing wall cavities is an art, to be sure, but there are many contractors who have been
doing it for years. In fact, there are now inexpensive ways to check with infrared cameras to make sure that all voids have been filled without disturbing the existing plaster or sheathing on outside walls. Because siding or shingles on old houses might also have worn out, we take the opportunity to install foam sheathing on the outside of the house before re-siding.*
6. Buy Energy Star (or better) fixtures, appliances, and lighting Once you have reduced your space-conditioning and waterheating loads, the lighting, appliance, and plug load will be your next big energy item. A new Energy Star refrigerator will use 20% less energy than a standard model. Replacing old light fixtures with pin-based
compact-fluorescent fixtures ensures that your electric bill will stay lower (up to 30%).
7. Add a renewableenergy source Once your energy consumption has been reduced significantly, it becomes reasonable to produce your own energy with systems such as photovoltaics, wind power, or hydro, if you happen to have a stream nearby. Until you slash the energy usage, though, it’s not worth the investment in renewable power sources. Conservation is still the cheapest game in town. *Go back to step 1 and reduce the size of the mechanicals. An airtight house with insulation on all six sides of the cube and good windows provides predictable performance, so the mechanical contractor won’t have to guess at the quality of the enclosure. Downsized mechanical equipment can defray the cost of steps 2-5.
district, so even though the chimneys were
the old rubble foundation with a perimeter
structurally unsound and the old slate roof
drain and a new slab. Adding insulation
was beyond its useful service life, they had
under the slab and inside the walls keeps
to be repaired (at a great cost) rather than
the space free of condensation and also
replaced.
saves energy.
Durability and Energy Efficiency Are Intertwined
illustrated on the following pages cost a
Making a flooded basement livable is a great
power sources to offset the remaining energy
The durability and functional upgrades
example of how one type of repair is directly related to another. On one of these projects, we needed to stop water from leaking into
lot. By spending a bit more, we were able to reduce energy costs tremendously. After cutting energy consumption, the stage is set for the installation of affordable, renewable needs. And that 21st-century step could transform these vintage homes to net-zero energy houses or even energy producers.
Can a Vintage Home Be Energy Ef ficient?
23
3-in. closed-cell spray foam (R-21) 3-in. fiberglass batts (R-10) 2-in. XPS foam (R-10) Tar paper
Wood sheathing Housewrap Blown-in cellulose (R-16)
1-in. XPS foam (R-5)
Wood siding
Our First Renovation Built in the 1860s, this house was a typical New England Greek-revival farmhouse. It had a basement prone to flooding, sagging
3⁄4-in.
furring strips create a drainage plane behind the siding.
floors, a leaning barn, and old, inefficient mechanical equipment. The structural and water issues were expensive to fix, so we looked for ways to save on energy upgrades. We took different approaches to fixing the
FOr the hOuse, three insuLatiOns under One rOOF To get a high R-value (R-40) without disrupting the roof or increasing the 2×6 rafter size, we combined insulation types. We could have used only closed-cell spray foam to fill the rafters, but at the time, it was too expensive. Instead, we used 3 in. of spray foam to create an air barrier and fiberglass batts to fill the rest of the rafter bay. A layer of rigid foam under the rafters is a thermal break.
house and the barn (see the drawings at left and on the facing page). Because we wanted to keep the barn’s timber-framing visible, all insulation went to the outside of the wall sheathing on the barn. On the house, we aimed to maintain interior finishes wherever
specs Built: 1860s renovation completed: 2,000 conditioned space: 2,600 sq. ft. before; 5,240 sq. ft. after, including the barn Bedrooms: 4 before; 6 after Bathrooms: 2 before; 41⁄ 2 after cost of renovation: $125 per sq. ft.
possible. annual utility cost: • Before: $1.90 per sq. ft.; after: 86¢ per sq. ft. • Gas: $3,000 a year before; $2,400 a year after • electric: $1,950 a year before; $2,100 a year after
Overall, our strategies worked. The house’s Energy Star rating for homes was 91 out of a possible 100 points (www. energystar.gov). We doubled the living area by bringing the barn and attached shed into the conditioned space while increasing power consumption by only 8%. We used
24
Energy Ef ficiency
12-in. screws 1⁄ 2-in.
a caLcuLated risk FOr the Barn Because we wanted the timberframing visible, we put the insulation outside the barn after wrapping it with plastic. Why plastic? Because structural and water-related repairs had drained our budget, and we thought we could save by using plastic (rather than selfadhesive roofing membrane) to control air and vapor while acting as a drainage plane.
plywood
10-in. EPS foam (R-40) 6-mil poly 3⁄4-in.
strips
plywood
Existing timber frame 8-in. EPS foam (R-32) 3⁄4-in.
strips
Existing sheathing
furring
6-mil poly
Wood siding
6×6 sill beam New 2×10 floor joist
the renovated barn as our office space for 10 years while fighting a zoning battle to allow this “commercial” use. In the end, we lost the zoning battle, and now the barn is a huge guest house with full kitchen and bath. We did what we thought we could afford at the time, but in trying to save money, we scrimped in ways we would not do again. The 6-mil polyethylene (see the drawing
8-in. EPS foam (R-32) Dense mesh drainage mat
where the roof leaked at the intersection of the new cupola that we installed. Today, we would use a peel-and-stick roofing membrane rather than plastic and be very dili-
2-in. closed-cell spray foam (R-14)
Roofing membrane Granite-block foundation
above) was a risky control layer for the barn and has been working except for some areas
2-in. metal stud wall with drywall
Embedded perimeter drainpipe leads to sump pump.
2-in. XPS foam
4-in. concrete slab
4-in. crushed stone (no fines)
gent with the flashing and counterflashing around the cupola. The waterproof membrane covering the basement wall was meant as a drainage plane for the granite-block foundation. We’ve learned that this is probably an unnecessary and expensive extra layer; the surface of closed-cell foam forms a hard skin that sheds water.
FiX FOr a FLOOd-prOne Basement The granite-block foundation in this 150-year-old barn quit blocking water many years ago. The solution? Pump it out. Peel-and-stick roofing membrane acts as a drainage plane, directing water to the perimeter drainpipe leading to a sump pump. Closed-cell insulation keeps the basement warm and dry. Can a Vintage Home Be Energy Ef ficient?
25
specs Built: Circa 1860 renovation completed: 2003 conditioned space: 2,150 sq. ft. before; 2,750sq. ft., after, plus 1,000 sq. ft. of dry warm basement space Bedrooms: 2 before; 41⁄ 2 after Bathrooms: 2 before; 41⁄ 2 after cost of renovation: $125 per sq. ft. annual utility cost: • Before: $2.34 per sq. ft.; after: 83¢ per sq. ft. • Gas: $3,600 a year before; $1,474 a year after • electric: $1,440 a year before; $830 a year after a deeper rOOF is cheaper tO insuLate Because the 2×4 rafters were sagging under the weight of the slate, we sistered 12-in.-deep rafters to them. Deep rafter cavities such as these mean that the more-economical opencell foam can be used and still get high R-values. Along with 2 in. of XPS (extruded polystyrene) under the rafters, we got an R-value of 50. Conditioned space behind the kneewall is ideal for air-handling equipment or ductwork. Two-inch-thick XPS foam board (R-10) adds insulation and is a class-II vapor retarder. Tar-paper baffle connects wall and roof insulation.
A Tricky Victorian This two-family Victorian house (circa 1860) was difficult to upgrade because we weren’t allowed to remove siding, replace the win-
Kneewall
dows, or dig into the slate roof.
Drywall is a code-required fire block.
The historic commission did, however, allow us to remove and replace the siding and windows on one wall where the siding was damaged and needed replacement, so 3⁄4-in.
Open-cell spray foam (R-40 in the rafters; R-14 in the walls) Housewrap 26
Energy Ef ficiency
strips
furring
Wood siding
we injected open-cell foam, added housewrap and furring strips, and replaced the siding on that wall. Historic commissions all over the country favor historical authenticity over durability and energy efficiency with regard
how much insulation do you need?
b
2-in. closed-cell spray foam (R-10) 2×3 wood stud wall 1⁄ 2-in.
drywall
2-in. XPS foam (R-10) 1-in. mesh drainage mat
Existing foundation wall
New 3-in. concrete slab
Existing concrete slab
ecause the earth is such a great buffer to heat loss and gain, the insulation needs in a house grow as you get farther from the ground. Naturally, they’re greatest at the roof, which is baked by the sun all day and chilled by the sky at night. We specify significantly higher levels of insulation than are required by the International Energy Conservation Code, and we think it is money well spent. When you’re attempting to approach net-zero energy use in homes, energy that isn’t used is always the cheapest energy.
r-10 under the basement Slab It is easy to add 2 in. or 3 in. of extruded (or expanded) polystyrene under a new slab before pouring the concrete. This could cut into headroom a bit, but the benefits outweigh the cost.
r-20 basement Walls a dry Basement tO BeGin With This house had no standing water in the basement, nor was there evidence of previous flooding. Because the basement had historically been dry, we didn’t install a perimeter drain and sump pump. Rather, we installed a drainage mat on top of the existing slab (to trap errant seepage) and placed 2 in. of rigidfoam insulation on top of that. We then topped the assembly with a new slab to make a warm, dry storage area.
Warming basement walls is often the best protection you can get from mold growth. Additional living space is an added benefit. Energy codes in most cold climates call for at least R-10, but if you can afford the additional insulation at this time, it is well worth it. Both closed-cell spray foam and rigid-foam insulation are good choices.
r-40 in the Walls By warming above-grade walls, you eliminate chilly convection currents inside a room, which can increase your actual living space because furniture no longer needs to be moved away from exterior walls. While the building code asks for at least R-19 in most cold climates, it is worthwhile to use as much insulation as you can afford.
to windows, chimneys, roof finishes, and other elements. Faced with these restric-
r-60 in the roof
tions, we compromised and used all-wood
Adding insulation to the roof (rather than the attic floor) brings extra living and storage space into the home at little cost. It also reduces summer cooling loads. It’s often easy to provide more than the code minimums because of deep rafter cavities. If you’re reroofing the house, consider putting rigid-foam board insulation on top of the sheathing as we did in two of the case studies here. After judging the performance of the first two houses, we increased our recommendation from R-40 to R-60.
simulated divided-lite replacement sashes for two-thirds of the window units. Because the openings were so far out of square, the sashes never fit quite right. We weren’t prepared for the battle over siding replacement. In the future, we’d like to replace the rest of the siding. When we do that, we’ll insulate with cellulose and foam sheathing.
Can a Vintage Home Be Energy Ef ficient?
27
Specs Built: 1915 Renovation completed: 2007 Conditioned space: 2,000 sq. ft. before; 3,600 sq. ft. after Bedrooms: 4 before; 4 after Bathrooms: 11⁄ 2 before; 31⁄ 2 after Cost of renovation: $100 per sq. ft.
28
Energy Ef ficiency
Annual utility cost: • Before: $1.68 per sq. ft.; after: 37¢ per sq. ft. • Gas: $2,400 a year before; $858 a year after • Electric: $960 a year before; $471 a year after
6-in. closed-cell spray foam (R-36)
Blown-in cellulose
Existing roof sheathing Two layers of 2-in. rigid polyiso foam (R-26) 1⁄ 2-in. plywood
insuLate Over and under the rOOF deck To get the most insulation into the shallow 7-in. rafters, we used closed-cell foam. On top of the roof, we added 4 in. of polyisocyanurate foam board, which has the highest R-value per inch of the rigidfoam boards. This yielded an R-60 roof without reframing. We didn’t want to disrupt the interior plaster to spray foam into the wall cavities, so we filled the walls with cellulose and covered them with rigid foam.
Existing sheathing Draining housewrap Two layers of 2-in. rigid polyiso foam (R-26) 3⁄4-in.
Draining housewrap
furring strip
Wood siding Metal flashing tucked under housewrap
Two layers of foilfaced polyisocyanurate insulation, seams staggered and taped (R-26)
repLacement WindOWs in thick WaLLs Tilt-in replacement frames are convenient because you don’t have to disturb the interior trim. But they don’t improve on the existing windows’ water resistance. You can integrate these windows into the drainage plane of your house with waterproof membrane.
New window trim
Expanding foam around perimeter of window
2×6 backing for window jambs New head, sill, and jamb extensions
New replacement window
Peel-and-stick sill flashing directs leaks to draining housewrap.
Blown-in cellulose
Third Time Is a Charm
New wood siding over 3⁄4-in. pressure-treated furring strips
This 1915 foursquare is an American classic found in almost every town in the country. Interior plaster was in great shape, the layout was excellent, and there was no structural damage to speak of. Other than adding
Better windows would be the next place
a few new windows to the back (for better
to reduce energy loads in this house. A
views to a pond) and updating the kitchen,
triple-glazed unit with heat-mirror technol-
we didn’t disrupt the interior too much. By
ogy might further reduce the heating load,
insulating the basement and roof, we almost
allowing us to get closer to zero.
doubled the living space of this house without adding an inch to the footprint. And the utility bills were cut by 60%.
Betsy Pettit, FAIA, is an architect and a principal of Building Science Corp., now located in the Victorian house featured here.
Can a Vintage Home Be Energy Ef ficient?
29
energy efficiency
1
Efficient Houses Need Fresh Air By MAX H. SHERMAN
I
people sick.” These assertions seem well
Houses Require Ventilation
founded: The most serious chronic illness
Before I go farther, let me define ventilation.
of American children is asthma, and the
The word ventilate comes from the Latin ven-
Environmental Protection Agency lists
tuilare, and it means to expose to the wind.
poor indoor-air quality among its top five
Although this might sound like some creep
environmental threats. Are tight houses
in a raincoat, the real story is more complex.
poisoning us?
Ventilation is used many ways when describ-
hear it all the time: “Houses are too tight.” “Houses didn’t used to make
There’s no disputing the cause-and-effect
ing how a house works: There’s crawlspace
relationship between tight houses and
ventilation (often bad), ventilated siding
indoor-air pollution. In theory, the solu-
assemblies (good), and roof ventilation
tion is simple: If you build tight, you must
(sometimes bad, sometimes good). We’re not
ventilate right. In practice, though, ventilat-
talking about that stuff. Here, we’re talking
ing right is complicated and controversial.
about mechanical ventilation, using fans to
In 2003, I chaired an American Society of
blow out old air (exhaust), suck in new air
Heating, Refrigerating and Air-Conditioning
(supply), or both (balanced ventilation).
Engineers (ASHRAE) committee that passed the country’s first residential ventilation standard. It gives builders and designers guidelines for providing good indoor air while keeping utility costs low (see the sidebar on p. 37).
Leaky Houses Are Not the Answer On average, the air in older homes is replaced once every hour (1 ACH, or air change per hour) because older homes have a built-in ventilating method that’s simple and reliable: leaks (or infiltration). The average house in the United States has about 3 sq. ft. of holes in it, but infiltration is a pretty bad way to ventilate because it wastes
a tremendous amount of energy. You could plaster that 3 ft. of holes with $20 bills, and the work would pay for itself in less than a season. Since the oil shock of the 1970s, houses are tighter and better insulated. Even conventionally framed new houses can be
Tight houses are energy efficient, but they need to breathe to be healthful and comfortable
5 times tighter than the general stock. Many builders and designers are tempted to take the Goldilocks approach and to look for a level of leakage that is just right, neither too little nor too much. Unfortunately,
indoor air needs to be cleaned.
there is no hole for all seasons. The best a
Flushing a house with fresh air
leaky house can do is waste energy much of
removes much of the indoor pollution.
the year and be underventilated the rest of the year. Won’t open windows provide the ven-
The most obvious way to control some contaminants is to isolate them. Paint thinner and other
tilation we need? In principle, yes, but in
poisons can be stored in a garden
practice, no. People are pretty bad at sensing
shed. Another way to control
exactly how much, how often, and for how
contaminants is to eliminate them from
long to open a window to provide optimal
the construction process: Use low-VOC
ventilation. Furthermore, noise, dirt, drafts,
paint, low-emitting carpet, and solid wood,
and creeps in raincoats dissuade people from
rather than particleboard, in furniture and
opening windows.
cabinetry. A third way to control the pollution level in a house is to exhaust spaces
Indoor Air Usually Is Dirtier Than Outdoor Air
where contaminants are produced, such as
Because indoor air starts as outdoor air, then
cally diluted with controlled whole-house
grows more polluted from contaminants in a house (see “Indoor Air Pollutants,” p. 32),
kitchens, laundries, utility/storage rooms, and bathrooms. But even after you’ve isolated, eliminated, and exhausted, there are still pollutant sources that are most practiventilation.
Backdrafting Pressurized/Depressurized
higher pressure When the inside of a house has a surized (think pres is than the outside, the house is blown into air n whe s pen hap This of a balloon). rior air into inte push to a tight house. The effect is the inside n Whe ng. ceili and s wall the openings in outside, the than sure of a house has a lower pres of lot a n whe s pen hap This d. urize it is depress with as h (suc se hou t air is exhausted from a tigh The air. eup mak any out with d) hoo e a large rang s wall the in s ning ope effect is to suck air through t mos and est bigg the g bein neys or ceiling (chim draf ting. obvious), potentially causing back
When air flows opposite the direction of its intended path, often through a flue or chimney, backdraf ting occurs. This can happen if a house is depressurized. In backdraf ting, contaminants are pulled into the house instead of being expelled, which can cause sickness or death.
Ef ficient Houses Need Fresh Air
31
Indoor Air Pollutants
A
ir pollution typically makes us think of smokestacks and exhaust pipes, but indoor air is usually dirtier than outdoor air. Listed below are some of the common pollution sources that argue for good whole-house ventilation.
Moisture Moisture is not a contaminant in the usual sense because water vapor itself is not an air-quality issue. But if the humidity is too high (as can happen easily in a tight house in a cold climate), it can lead to condensation, which can cause problematic mold and fungi to grow.
Consumer products Toxic chemicals (such as pesticides, paint supplies, and cleaning supplies) that are stored around the house can cause health problems. These items aren’t limited to the garage and the cleaning-supply cabinet; many consumer products such as cosmetics and “air fresheners” also can cause indoor-air pollution.
Building materials Volatile organic compounds (VOCs) may or may not be considered toxic, but they are the largest class of chemicals found in indoor air. The most common VOC is formaldehyde from glues used in engineered-wood products, such as particleboard. Synthetic carpet and oil-based paint are other sources of indoor VOCs.
Good Ventilation: Different Paths to the Same Place When ventilation removes contaminants, it’s your friend, but in doing so, it usually brings in outdoor air that must be heated, cooled, or dehumidified, which costs money. Just because it costs money, though, doesn’t mean ventilation is your foe. The energy savings of a tight house more than offset the operating cost of a small fan, not to mention the costs of asthma and allergy medications. The trick is to design a ventilation system that provides acceptable indoor air as efficiently as possible. The system’s design depends on where you live, but the ASHRAE ventilation standard can guide you through alternatives. Every ventilation system likely will be a little different. In general, though, there are three approaches to whole-house ventilation—exhaust, supply, and balanced systems—each a little more involved and more expensive than the last.
Exhaust Ventilation Clears Pollutants at Their Source The simplest system, exhaust only, provides
Biological sources
mechanical ventilation with a continuously
Pets, dust mites, mold, and other nano-critters are not contaminants by themselves, but the particles they shed can cause various kinds of allergic reactions and/or asthma. Mites and mold require specific moisture and temperature conditions to grow and usually can be controlled by controlling the humidity. Bioeffluents from pets can be difficult to control.
operating exhaust fan (see the drawing on the facing page). This fan can be as simple as upgrading your bath fan or as complex as installing a multi-room exhaust fan. The exhausted air is replaced by air infiltrating through leaks (in humid climates, this can cause moisture problems). But rather than
Smoke
doing so at the whim of the weather, it is
Smoke from candles, tobacco, and frying fish contains particles (soot and ash), VOCs, and other gaseous contaminants in addition to semi-VOCs, many of which can cause health problems.
being done at a steady level with the fan. With the quiet, energy-efficient fans available today, this option is cheap and easy. Because its makeup-air requirements are small, a low-volume exhaust fan won’t depressurize your house enough to cause backdrafting. This system also has the advantage that it can be used in homes without ductwork.
32
Energy Ef ficiency
An Exhaust-Only System Removes the Bad Air The simplest way to make sure contaminants don’t build up in a house is to suck them out with one or more continuously running exhaust fans. This approach is the least expensive, is the least invasive, and has the advantage of working in houses without existing ductwork. For whole-house ventilation, existing kitchen and bath fans must be left running, a noisy prospect unless you have super-quiet models. A better solution is to use a multiport fan (see the drawing on p. 36) in the attic to exhaust many rooms simultaneously.
Exhaust fan
Passive-intake vents provide replacement air.
Laundry room
Air leaks provide unreliable replacement air. Air polluter
Pull cord opens and closes vent.
PASSIVE INTAKE In this exhaust-only system, makeup air comes in through open doors and windows, or through leaks if you have a leaky house. If you have a tight house, passive vents serve the same purpose. The Therma-Stor® fresh air inlet pictured here comes from www.efi.org and costs about $37. Similar vents are available from American Aldes Ventilation (www.americanaldes.com).
Ef ficient Houses Need Fresh Air
33
Three Design Choices for Hot, Humid Climates
i
A downside is that this system blows out heated (or cooled) air and, therefore, wastes energy. Another downside is that you don’t
n a hot, humid climate, drawing fresh air into a house can be a problem. You can inadvertently introduce 8 gal. of water a day from ventilation air. When combined with internally generated moisture sources, this is way too much. There are three design options to consider or combine.
know where the ventilation air being sucked
1. Tolerate
Supply Ventilation Dilutes Pollutants Throughout the House
You can accept periods of high moisture levels if you use moisture-tolerant materials. Hard, cleanable surfaces are better choices than fuzzy ones. Use hardwood floors instead of carpet, or tile, plaster, or brick rather than paperfaced drywall.
in is coming from (or where it has been). Air from a garage or other polluted space shouldn’t be inadvertently brought into a house. Passive-intake vents are a simple way to offset this problem (see the photo on p. 33).
A supply system has the advantage of allowing you to select where the air comes
2. desiccate
from and how it is distributed throughout
Get the extra moisture out of the air by condensing it and draining it. Air conditioners can remove moisture, but they usually are sized and designed for controlling temperature. In some climates, they won’t dehumidify enough under normal use. A better option is a standalone dehumidifier or enhanced dehumidification gear.
your home. For example, fresh air can come from a duct run connected to the return plenum of an HVAC system (see the drawing on the facing page). This way, outdoor air is pulled into the house through the air handler whenever it operates. Such an air intake must have controls (such as a timer or cycler) to turn on the air handler to make sure there is enough ventilation air. This sys-
3. procrastinate Some humid climates have dry seasons. It might be possible to use reservoir-type buffer materials that store moisture during hot, humid periods, then release it during dry ones. Examples of such materials are brick interior walls, cellulose insulation, and solid-wood exposed beams.
tem also should have a damper to prevent overventilating when the heating or cooling system is operating most of the time (very hot or very cold weather). Without these controls, this supply system is just a hole in the return duct, worse than a leaky house. Supply systems must temper ventilated air to moderate temperatures in all but the mildest climates. When there is no heating or cooling call, the system above does this by running the air handler and mixing unconditioned outside air with large volumes of conditioned indoor air. While this process tempers the outside air, it uses a lot of electricity because the air-handler fan is overkill for the amount of ventilation air being sucked in.
34
Energy Ef ficiency
A Supply System Removes Bad Air and Brings in Fresh Houses with a forced-air heating system or with central air-conditioning have a built-in air-distribution network. A supply system uses it to distribute fresh outside air through the existing ductwork. But you still need exhaust fans in wet rooms. The best approach is a quiet, continuously running multiport vent fan in the attic that draws from several rooms (see p. 36).
Exhaust fan
Laundry room
A separate range-hood vent fan is the simplest, best way to deal with contaminants from cooking.
Air polluter
A damper shuts down air intake during temperature and humidity extremes.
Fresh air is brought in through a separate duct running from the outside to the return-air plenum of the HVAC unit.
ACTIVE INTAKE With a duct from outside the house to the furnace’s return-air plenum, fresh makeup air is drawn into the house by the furnace fan. A temperature- and humidity-sensing damper system (pictured at left) installed in the duct curtails airflow during very hot and humid or very cold weather.
Ef ficient Houses Need Fresh Air
35
A Balanced System Removes Bad Air, Brings in Fresh, and Can Save Heat (or Cold) The problem with exhausting stale air from your house is that you’ve likely paid good money to heat or cool that air, and venting it directly outside is like throwing away money. A balanced system with a multiport vent fan (from $185 at www.sheltersupply.com or www.iaqsource.com) Exhaust duct channeling leads to HRV. all exhaust through some type of heat exchanger can mitigate the Return air energy loss. for furnace
Multiport fan vents problem areas.
A separate range-hood vent fan is the simplest, best way to deal with contaminants from cooking.
Air polluter
After giving up its heat inside the HRV, stale air is exhausted outside.
Return-air plenum
HRV uses heat from exhausted air to warm incoming air.
Outside-air intake sucks fresh air into the HRV, where it is tempered before it enters the return-air plenum.
ACTIVE EXHAUST AND INTAKE WITH ENERGY RECOVERY The best approach to whole-house ventilation employs either a heat-recovery ventilator (HRV, from $700; see the photo at left) in cold climates or an energy-recovery ventilator (ERV, from $800) in hot climates. These units, which can be incorporated into a house with or without existing ductwork, bring in fresh air and exhaust stale air. In addition, an HRV tempers incoming air with outgoing air, thus lowering the amount of energy necessary to condition the fresh air. An ERV looks and functions similarly, but it dehumidifies and cools hot, humid air, which reduces the load on the air conditioner.
36
Energy Ef ficiency
America’s First Residential Ventilation Standard
U
ntil recently, not much had changed since 1631, when England’s King Charles I passed the first ventilation code (your dwelling had to have operable windows taller than they were wide). Because today’s houses aren’t leaky enough to provide fresh air, the American Society of Heating, Refrigerating and Air-Conditioning Engineers wrote a ventilation standard. ASHRAE 62.2 is a minimum standard applicable to both new and existing homes (including small multifamily ones). Keep in mind that 62.2 is a standard, not a code. Think of it as a recommendation that might lead to a new code requirement.
The major requirements of 62.2: •Whole-house mechanical ventilation Ventilation can be achieved with an exhaust, supply, or balanced ventilation system. Ventilation airflow, measured in cubic feet per minute (cfm), must increase with the size of the house and the number of occupants. The 62.2 standard recommends minimum ventilation rates of 45 cfm for 2- to 3-bedroom houses up to 1,500 sq. ft.; 60 cfm for 2- to 3-bedroom houses between 1,500 and 3,000 sq. ft.; and 75 cfm for 4- to 5-bedroom houses between 1,500 and 3,000 sq. ft.
•Mechanical exhaust in kitchens and bathrooms In addition to the whole-house ventilation requirement: Kitchen: a user-operable vented range hood of at least 100 cfm; or a fan giving 5 kitchen air changes per hour of continuous or intermittent exhaust. Bathroom: a user-operable fan of at least 50 cfm; or a continuously operating 20-cfm exhaust fan.
•Minimum performance standards for fans Volume: Fan’s airflow rates must be rated by a third party. Noise: Continuously operating fans should be 1 sone or less; intermittent-use kitchen and bath fans cannot exceed 3 sones.
•Airtight garage duct systems Air handlers or return ducts in an attached garage must be tested for tightness. While tight ducts save energy, 62.2 sets only minimum requirements to protect indoor-air quality.
•Particle filtration upstream of air handlers Dirty ducts and coils can become a pollution source, so 62.2 requires pleated furnace filters (MERV 6 or better). To clean the air inside a house, more-aggressive filtration is needed.
Balanced Ventilation Brings in the Good Air, Banishes the Bad, and Conserves Energy
thereby reducing the HVAC energy cost. An
The best way to temper incoming air while
that the air conditioner has to do.
HRV heats or cools incoming fresh air and can recapture up to 80% of the energy that would be lost without it. ERVs are better suited for hot, humid climates because they dry incoming air, thus reducing the work
reducing HVAC energy consumption is to
systems (see the drawing on the facing
You Still Need to Clean Up
page) are balanced approaches that use the
Ventilation is good at diluting gaseous com-
temperature and humidity of an exhaust-air
pounds and small particles because small
stream (which otherwise would have been
particles act like gases. They mix quickly in
wasted) to temper the air of a supply stream,
the air and follow air currents when air is
use a heat-recovery ventilator (HRV) or an energy-recovery ventilator (ERV). These
Ef ficient Houses Need Fresh Air
37
expelled. But large
Tempered Air
Outdoor air mixed with indoor air has a temperature that is not objectionable (but not necessarily comfor table). For example, a dedicated outdoor-air system might temper 1 part of the incoming outdoor air with 3 parts interior air in the supply plenum before supplying it to a home’s occupied zones.
particles such as pollen, pet dander, and dust mites must be cleaned up or vacuumed rather than exhausted or diluted because they’re too heavy to mix with air. Other large particles, called semi-VOCs, are solids or liquids at room temperature. While they’re not gaseous, as
with VOCs, they are volatile enough to emit lots of gaseous vapor. This is important, because if you filter out SVOC particulates you haven’t really done anything until you clean the filter; the SVOCs keep emitting gaseous vapor from the filter. If you don’t replace filters on your HVAC system regularly, the system itself becomes a contamination source. The three ventilation systems discussed here are by no means comprehensive; they can be combined in various recipes to meet particular conditions. In addition to climate and house tightness, cost can be a big consideration, but it shouldn’t be the major one. Be sure to consider long-term durability and maintenance requirements. Systems with heat recovery (HRV/ERV) require a lot more maintenance than those without. Systems with multiple filters or requiring seasonal adjustment can be confusing.
38
Energy Ef ficiency
Tight Houses Are Good, and They Should Breathe Excessive leaks are one way for a house to breathe, but not the best. While there’s a lot of ongoing research and a robust scholarly debate on the best way to achieve acceptable indoor-air quality, building scientists all agree that houses need to breathe. As houses become higher and higher performance, they need to breathe in a steady, reasonably controllable way. We cannot afford to let them breathe at the whim of the weather or with windows only. We also sometimes need to be able to have them hold their breath when conditions outside are exceptionally bad. Only with designed ventilation systems can we make sure that indoor-air quality and energy efficiency advance hand in hand. Dr. Max H. Sherman is a consulting building scientist and physicist at Lawrence Berkeley National Laboratory in Berkeley, Calif.
A Practical Look at Deep-Energy Retrofits By Martin Holladay
I
f you pay any attention to building sci-
tical and cost-effective measures to make
ence, you have probably seen the term
any home tighter and more efficient.
“deep-energy retrofit”—a phrase being “sustainability” and “green.” Like the word
How Deep?
“green,” the term “deep-energy retrofit” is
No standard-setting agency has established a
poorly defined and somewhat ambiguous.
legal definition of a deep-energy retrofit, but
In most cases, though, “deep-energy retro-
the term generally refers to retrofit measures
fit” is used to describe remodeling projects
that reduce a home’s energy use by 50% to
designed to reduce a house’s energy use by
90% below that of a code-minimum house—
50% to 90%.
or, according to a more lenient definition,
thrown around with the colloquiality of
Remodelers have been performing deep-
below preretrofit levels. Probably fewer than
energy retrofits—originally called “superin-
100 homes in North America have completed
sulation retrofits”—since the 1980s. Most
deep-energy retrofits that conform to the
deep-energy retrofit projects are predomi-
strictest definition of the term.
nantly focused on reducing heating and
A house that has undergone a deep-
cooling loads, not on the upgrade of appli-
energy retrofit typically ends up with R-20
ances, lighting, or finish materials.
basement walls, R-40 above-grade walls, R-60
While a deep-energy retrofit yields a
roofs, and U-0.20 windows. A typical air-
home that is more comfortable and healthy
tightness goal, determined by a blower-door
to live in, the cost of such renovation work
test, is 1.2 ACH (air changes per hour) at
can be astronomical, making this type of
50 pascals.
retrofit work impossible for many people.
A deep-energy retrofit doesn’t make sense
Those of us who can’t afford a deep-energy
in all climates, and not every home is a good
retrofit can still study the deep-energy ap-
candidate for the work. Cold-climate homes
proach, using it to shed light on more prac-
often have higher energy bills than homes in more moderate climates, so a cold-climate
energy efficIency
1
An old house with a new shell. This deep-energy retrofit in Somerville, Mass., received 4 in. of spray polyurethane foam on its exterior. (For more information, see the case study on p. 45.) However, not all energy upgrades have to be so elaborate.
40
Energy Ef ficiency
home may be a better candidate than a home in a moderate climate or a home that
Phases
already has low energy bills. A house with a simple rectangular shape and a simple gable roof is easier and less expensive to retrofit than a house with complicated exterior elevations, bay windows, dormers, or a roof full of hips and valleys. Most of the deep-energy retrofits include the installation of a new layer of exterior insulation. Intricate architectural details add to the difficulty of such retrofit work, driving up costs. Homes with simple exterior trim and uncomplicated cornice details are much easier to work on than Victorian homes with gingerbread trim. Because many deep-energy retrofits require existing roofing and siding to be replaced, the best candidates for deep-energy retrofit work are houses that are in need of new roofing and siding.
The Payback Homeowners who undertake deep-energy retrofits are usually motivated by environmental or energy-security concerns rather than a desire to save money on their energy bills. These jobs are so expensive—in the range of $50,000 to $150,000 per house—
1. Get an energy audit. An auditor will evaluate your home and develop a list of energy-retrofit measures (see “Every House Needs an Energy Audit,” pp. 4–11). 2. Perform air-sealing work, using blower-door test results to direct you. 3. Install a mechanical ventilation system once you’ve tightened up the building envelope. 4. Start insulating the home from the top, because a lot of heat is lost through ceilings and roofs. 5. Insulate the interior side of basement walls, a relatively easy task because basement walls are accessible. 6. Install dense-pack cellulose insulation into any empty stud bays of above-grade walls. This work is affordable and cost-effective. 7. Install thick rigid foam on the exterior of the sheathing and new high-performance replacement windows. 8. Finally, install a new heating system. This should be done last, because the unit should be sized for your new high-performance home. If a new heating unit is installed earlier in the project, it’s likely to be too big.
that a homeowner would have to wait decades before the investment could be recouped. “In a retrofit situation, it can cost a lot of money to save a small amount of energy,” says energy consultant Michael Blas-
tribution to a home’s energy performance,
nik. “Going from R-19 to R-40 walls or R-30
they may greatly enhance the home’s aes-
to R-60 ceilings doesn’t save a whole lot of
thetics and value.
Btu—and the cost of that work is potentially tremendous.” There’s no easy way to calculate the
Those of us without a Midas budget will need to settle on a less ambitious approach to energy savings than a full-blown deep-
payback period for many deep-energy ret-
energy retrofit, and that’s OK. Less expensive
rofits, in part because a major overhaul of
and less invasive retrofit measures, typically
a building’s shell inevitably includes many
referred to in the industry as weatherization,
measures (for example, adding new siding or
have payback periods of 15 years or less.
roofing) that aren’t energy-related. Although these elements don’t make a significant con-
A Practical Look at Deep-Energy Retrofits
41
Energy Retrofits of All Levels
Practical approach It’s much less expensive
Paul Eldrenkamp is a Massachusetts remod-
air leakage before dragging a cellulose hose
eler who has performed several deep-energy
into the attic. Seal all ceiling leaks under the
retrofits. When his clients balk at the high
existing insulation (for example, at electrical
cost of a full retrofit, he sometimes advises
and plumbing penetrations, at utility chases,
them to work in phases. Although it is com-
and at the gaps between partition drywall
mon to perform energy improvements over
and partition top plates). It’s also important
time as finances permit, it’s also important
to be sure that there are no air leaks at the
to take advantage of upgrade opportunities
perimeter of the attic, where the ceiling air
even if they seem to fall out of sequence. For
barrier meets the wall air barrier.
example, if you have to install new siding
Performance comparison While there is
or roofing and you do so without installing
no upper limit on the R-value that can be
thick rigid foam underneath, you may regret
achieved when installing foam on top of the
your shortsighted decision in time. Here’s a
roof sheathing, the maximum R-value of
general overview of the work to be done, the
attic-floor insulation depends on the available
order in which it should be completed, and
height at the perimeter of the attic. Achieving
the practical alternatives to going deep.
R-60 requires about 16 in. of cellulose.
Roof Insul ation
Cost comparison Attics with easy access are
Deep-energy retrofit Many deep-energy
easier and cheaper to retrofit than cluttered
retrofits call for insulating a roof to R-60,
attics with lots of penetrations that need to
which can most easily be done by adding
be sealed. From a material standpoint, the
4 in. of rigid polyisocyanurate foam on top
practical approach is almost always more
of the roof deck and then filling each rafter
economical. For any given R-value, poly-
bay with loose fill or batt insulation. Exte-
isocyanurate costs from three to five times
rior foam sheathing has the added benefit
as much as cellulose insulation. Needless
of reducing thermal bridging through the
to say, adding rigid foam on top of the roof
rafters.
sheathing includes significant expenses for
to install cellulose on an attic floor than to install rigid foam and new roofing. Address
roof demolition, new roof sheathing, and new roofing—costing between $3 and $5.80 per sq. ft.
Basement insul ation Deep-energy retrofit After addressing any moisture issues in the basement, many deepenergy retrofits call for basement walls to be insulated to R-20, requiring the addition of 4 in. of XPS insulation or about 3 in. of
Pile it on. If adding rigid foam on top of the roof sheathing isn’t an option, a less expensive option is blowing cellulose on an air-sealed attic floor. The more insulation, the better.
42
Energy Ef ficiency
Retrofit Results
Stop the leaks. If a full basement-insulation job isn’t in the budget, attack the rim joist. Spray polyurethane foam works best, but a more affordable option is to seal rigid-foam panels in each joist bay with canned spray foam. closed-cell spray polyurethane foam. The rim joists are also insulated with either spray foam or rigid foam. The basement floor is insulated with
Location: Arlington, Mass. Size: 3,000 sq. ft. (duplex) Renovation cost: $47 per sq. ft.; $140,000 total
Cost: $140K Annual savings: $2,300 While planning a deep-energy retrofit of his 3,000-sq.-ft. twostory duplex in Arlington, Mass., owner Alex Cheimets got a lucky break: He was eligible to participate in a pilot superinsulation program sponsored by the Massachusetts Department of Energy Resources and his local utility.
2 in. to 4 in. of XPS foam over the slab. A new subfloor is applied over the foam.
Construction
Mechanicals
Practical approach Adding insulation to
Basement: Ceiling sprayed with open-cell spray polyurethane foam (adds thickness and R-value)
Heating: Oil-fired steam boiler in each unit
the basement walls and rim joists is cost effective in all northern climates. However, the payback period for basement-floor insulation is much longer than for basementwall and rim-joist insulation, so it’s often eliminated in projects with a limited budget. Performance comparison Since the temperature of the soil under a below-grade slab is higher than the average outdoor-air temperature in winter, heat loss through a basement slab is much less than through a basement wall. In many homes, basement slabs are responsible for less than 1% of a home’s total heat loss. Cost comparison Not insulating your basement floor saves you from $1.80 to $2.50 per sq. ft. in materials.
Walls: 2×4 construction filled with cellulose; 4 in. of foilfaced polyisocyanurate foam outside of sheathing for a total of R-39 Roof: 6 in. of polyisocyanurate insulation installed above the existing roof sheathing, topped with a layer of plywood; 8 in. of open-cell spray polyurethane foam (Icynene) installed between the existing rafters for a total of R-59 Windows: Double-pane (U-0.33) windows by Pella®
Water: Main boiler in unit 1; on-demand gas water heater in unit 2 Ventilation: Heat-recovery ventilators (one for each apartment)
Results Energy reduction: 65% (heating fuel) Annual savings: $2,300 per year Payback period: 61 years. If the cost of the roofing and siding are subtracted, payback is reduced to a little over 35 years.
A Practical Look at Deep-Energy Retrofits
43
Windows
Air-seal, then insulate. If you can’t afford to add insulation to your walls, address simple air-sealing measures such as filling the gaps around windows, electrical boxes, doors, and recessed lights in the ceilings.
Deep-energy retrofit Single- or doubleglazed windows are usually replaced with new triple-glazed windows with fullthickness (13⁄ 8 in.) glazing. This glazing is better than thin 7⁄ 8-in. or 1-in. glazing. Practical takeaway The cost of installing high-quality replacement windows can be staggering; as a less expensive alternative, consider installing low-e storm windows over tuned-up windows in good working order and that have been weatherstripped. Performance comparison Good tripleglazed windows have a U-factor of 0.17 to
Wall Insul ation
0.20. A low-e storm window won’t achieve
Deep-energy retrofit A typical 2×4 wall
the same performance. Installed over a
insulated with fiberglass batts has a whole-
single-pane wood window, a low-e storm
wall R-value of about 10. Many deep-energy
window provides a total U-factor of 0.40,
retrofits aim to insulate walls to R-40, which
while a low-e storm window installed over a
typically requires all of the siding to be re-
double-pane wood window provides a total
moved and the addition of 4 in. to 5 in. of
U-factor of 0.34. (The lower the U-factor,
polyisocyanurate rigid insulation or spray
the better.)
polyurethane foam.
Cost comparison The cost to install a low-e
Practical takeaway Unless your home’s
storm window ranges from $120 to $160.
existing siding is in bad shape, it’s hard to
The installed cost of a new triple-glazed win-
justify the cost of installing exterior wall
dow is about $800 to $1,200.
foam. If your existing siding is sound, your best retrofit option is careful air-sealing work from the interior with canned spray foam. Typical leakage areas include the gap between the baseboard and the finished floor; electrical boxes; and cracks behind window
rofits include air-sealing measures. Once infiltration rates have been reduced, an older house requires a good mechanical ventilation system. Options range from low-sone
Performance comparison Above-grade
to heat-recovery ventilation systems with
thermal envelope, and an R-10 wall leaks heat at four times the rate of an R-40 wall. Although air-sealing an R-10 wall will surely increase its performance, it will not rival an R-40 wall.
bathroom exhaust fans controlled by timers dedicated ductwork. A new heating unit is also a quintessential upgrade in many deep-energy retrofits. New furnaces or boilers are most often efficient sealed-combustion models. The fuel type is relatively unimportant, because the
Cost comparison Installing thick exterior-
fuel demands of the newly renovated home
wall foam and new siding on a typical house
will be low.
costs tens of thousands of dollars. Blower-
Practical takeaway If you’ve done any
door-directed air-sealing work might cost $700 to $1,000 per house.
Energy Ef ficiency
Deep-energy retrofit Most deep-energy ret-
and door casing.
walls represent most of a typical house’s
44
HVAC
air-sealing work, a mechanical ventilation system is essential. Exhaust-only systems are
much less expensive than a system with a heat-recovery ventilator. If you can’t afford
Retrofit Results
an HVAC overhaul, you should at least have
Location: Somerville, Mass. Size: 2,966 sq. ft. (duplex) Renovation cost: $50 per sq. ft.; $148,300 total
ducts tested for leakage and sealed. Performance comparison Replacing an 80% AFUE (annual fuel utilization efficiency) furnace with a 92% AFUE furnace will cut energy use 13%. Sealing ducts may save an additional 5% to 20% of your energy use. Cost comparison The installed cost of a new 92% AFUE furnace ranges from $3,000 to $6,000. Duct sealing and repair costs between $250 and $500 per house. Martin Holladay is a contributing editor to Fine Homebuilding.
Cost: $148K Annual savings: $2,490 Alarmed by the implications of the global climate-change crisis, Cador Price-Jones embarked on a major retrofit of his Massachusetts duplex (also pictured on p. 40).
Tight ducts save money. Sealing leaky ductwork can be done in several ways, but mastic and fiberglass-mesh tape are among the best options.
Construction
Mechanicals
Basement: 3 in. of closed-cell spray foam (R-18) applied between the studs of a 2×4 wall built against an 8-in. block foundation
Heating: Modulating condensing gas boiler, 22,700- to 75,200-Btu rated output, 95% AFUE
Walls: Existing 2×4 walls filled with dense-pack cellulose; new 2×2 frame installed on exterior and filled with 4 in. of closed-cell spray foam for a total of R-37 Roof: Attic floor air-sealed and filled with 17 in. of loose-fill cellulose for an R-value of 60; 2 in. of spray foam used to air-seal the eaves Windows: Main house windows are double-glazed, low-e, argon-filled units by JeldWen®; basement windows are double-glazed hopper units by Harvey Industries
Water: 60-gal. Superstor® indirect hot-water tank Ventilation: Heat-recovery ventilators (one for each apartment) Photovoltaic: 5.25kw package system by Nexamp™
Results Energy reduction: From $5,650 per year to $3,160 per year Annual savings: $2,490 Payback period: 60 years
A Practical Look at Deep-Energy Retrofits
45
insulation
2
Upgrade Your Attic Insulation BY MIKE GUERTIN
S
aving money on heating-fuel costs is a
I typically focus my efforts to improve
lot simpler than negotiating with OPEC
the energy efficiency of an attic in two areas:
or your local utility. Here’s how: On a recent
sealing air leaks in the ceiling and increasing
upgrade in the attic of a 1950s-era house
the amount of insulation in the attic itself.
(one of two projects that is featured here), I
The payback period for tightening a leaky
air-sealed and spread a 12-in.-deep layer of
ceiling can be as short as a month. Add-
cellulose throughout 1,500 sq. ft. of space in
ing insulation might take a few heating or
about a day. As a result of this and other
cooling seasons to pay off, but the wait is
energy-saving improvements that were made
relatively brief. I estimate the payback for
to the home, the owner saw his heating and
air-sealing and upgrading attic insulation to
cooling costs reduced by half compared to
be realized in three years.
the previous year, even in the face of higher electricity and heating-fuel costs.
On these projects, I often chose to install a radiant reflective membrane. Besides
reducing radiant-heat gain from the roof, the membrane makes the attic more
Attic Work Safety
attractive and dust-free for storage use, and it keeps the blown-in insulation I use from blocking the rafter bays. While radiant barriers can reduce peak attic temperatures by 10°F to 30°F, they haven’t proved to be cost effective in all geographic regions or in attics that are adequately insulated, that are air-sealed, and that have well-insulated, wrapped air-handling equipment and ductwork. In these cases, you may be better off spending the money on more insulation and air-sealing than on a radiant barrier.
Stop the Air Leaks, Stop Losing Heat Air leaks can account for 30% of a home’s energy loss, so it pays to seek out and seal every penetration between the living (conditioned) space and the attic (unconditioned) space before adding insulation. Don’t leave any batt unturned when hunting down air leaks. Dust deposits in leaking air stain in-
W
orking with insulation is about balancing safety and comfort. Although official health warnings are ambiguous at best, it’s a good idea to err on the side of caution, especially regarding fiberglass. You might see photos of me without a long-sleeved shirt or, occasionally, gloves, but not without a mask; when it’s 100°F in an attic, I’ll sacrifice some itching to stay cooler. • A respirator and safety glasses are necessary in any situation. • When handling fiberglass, it’s a good idea to wear long pants and a long-sleeved shirt, or a one-piece work suit. If your hands are sensitive, wear gloves. • Step only on ceiling joists, never on the ceiling. Use kneeboards that span between ceiling joists for more freedom and stability. • Work in the cool of the day, early morning or evening when the sun isn’t beating on the roof (in the summer, of course).
sulation brown or black, so you can start by looking for discoloration in the insulation. I treat the drywall ceiling as the air barrier and seal all penetrations, joints, and holes. The open framing for soffits and chases is a highway for air leaks from wall cavities into the attic. Another gaping hole is the attic-
electrical boxes should be sealed to the dry-
stair bulkhead (see the sidebar on p. 53).
wall with a fire-resistant sealant or foam (see
I install an insulated and gasketed cover
the sidebar on p. 49). Gaps around ducts,
for the attic access panel or pull-down stair-
wires, and pipes that penetrate into the attic
way. You can buy a ready-made access cover
must be located and closed, too. Most
or make your own. The cover can be fit
inexpensive and old bathroom exhaust-
within the riser or on top of it. When
fan boxes have open seams and holes that
the cover sits on top of the riser, apply the
should be covered with mastic or duct-
gasket material (usually adhesive-backed
sealing tape. The fan-box perimeter should
foam tape) to the cover (not the floor) so
be sealed to the drywall with caulk or foam.
that it’s not damaged when someone accesses the attic. Next, I seal recessed-light cans and
Another typical area to block off and seal is the 2-in.-wide space between framing and masonry chimneys. Combustible materials
ceiling-mounted light-fixture boxes. Both are
aren’t allowed to contact the masonry, so it’s
often overlooked, but when combined are
best to use sheet metal to block the space.
one of the biggest sources of air leaks. The holes and the perimeter of ceiling-mounted
I also seal the joint between the drywall and the wall plates. The thin joints between Upgrade Your Attic Insulation
47
Potential Air Leaks in the Attic Below is a checklist. 1. Recessed lights and electrical boxes 2. Holes for wires or pipes in drywall and framing 3. Attic hatchway 4. Spaces between the framing and the chimney 5. Plumbing or electrical chases 6. Framed soffits that are open to the attic 7. Drywall joints between ceiling and wall plates 8. Leaky joints in ductwork
If air leaks aren’t properly sealed, the insulation typically placed between the ceiling joists of a conventional attic is only partially effective. These leaks can range in size from a pinhole to the gap surrounding the typical 3-ft. by 4-ft. access hatch. For the contractor or homeowner who wants to create a tighter building envelope, the hardest part of the task is finding the air leaks; sealing them is relatively easy.
A word of caution: Air-sealing a house can lead to backdrafting of natural draft combustion appliances like water heaters, furnaces, or boilers. To avoid creating a carbon-monoxide hazard, have a combustion-safety assessment done before tightening a house, and add a fresh-air intake duct to each burner.
8
4 1 5
2
48
Insulation
3
7
6
the ceiling drywall and the wall top plates might seem insignificant, but they add up when you figure the linear footage of walls. Expanding foam or sealing caulk easily fills the gaps.
Address Wiring Issues Because old knob-and-tube wiring can’t be buried under new insulation, have an electrician replace any old wires in the attic before adding insulation. Ideally, all junction boxes should be raised above the level of the insulation. When elevating the junction boxes isn’t an option, you should install clearly marked permanent tags that can be seen above the insulation level. While I am working in the attic, I like to install two electrical conduits (one line voltage and one telecom/low voltage) between the attic and the basement or the crawlspace to make any future wiring upgrades easier to accomplish.
Tune Up Existing Insulation The two types of insulation that are usually found in older attics are fiberglass batts and loose-fill cellulose. For batt insulation to perform at its rated level, it must be installed snug to the ceiling surface and to the edges of the framing. Any gaps or voids reduce the insulation’s effectiveness. If the existing insulation is in good condition, it can be reused. I tune up the insulation by tightening end joints, making sure batts are tight to the ceiling drywall, and filling in any voids with new pieces of insulation. If I’ve decided to increase the amount of insulation with more batts, I like to bring the level of the older batts flush with the top of the joists and then install a new layer of unfaced batts running perpendicular to the joists. Placed above the joists, the cross-
Choose the Right Air Sealant for the Job
W
hen I’m air-sealing an attic, I use four or five different types of sealants. I use caulk when I need precision: caulking a recessed-light can to the ceiling drywall, for instance, or sealing some pieces of rigid foam to framing. Where gaps around pipes or wires need filling, I use expanding urethane foam. The distinctions become finer when I’m sealing leaks that come under the code heading of draft-blocking or firestopping. (In many areas, local fire codes supersede the International Building Code, so be sure to check them first.) Draft- or fireblocking refers to stopping smoke or fire from passing from one area to another through perforations in floors, walls, and ceilings. These caulk or foam sealants typically are used to seal holes and gaps in top plates, for example, that could compromise the integrity of the wall’s fire-blocking. Fire-stopping or fire barrier refers to sealants classified as intumescent: When exposed to direct flame or heat, they expand to fill the cavity and are rated to withstand direct flame.
Fire-blocking foam DaP® www.dap.com
Fire-blocking caulk 3M® www.3m.com
Fire-barrier caulk 3M
(continued on p. 53)
Upgrade Your Attic Insulation
49
The Space around the Chimney Needs a Fire-Resistant Seal
T
here’s usually a 2-in.-wide gap, required by code, between framing and masonry chimneys. To close the gap, I first stuff it with rockwool (1), then apply a bead of adhesive caulk to the framing (2). Next, I screw down wide strips of metal (recycled drip edge)
along the perimeter (3). I seal the metal to the chimney with fire-rated intumescent caulk (4). For continuity, you need to seal the ceiling joists to the drywall below and at inside/outside corners of the rough opening with expanding foam.
1
2
3
50
Insulation
4
Small Leaks Add Up, So Seal Them All
U
sually, the greatest number of leaks comes from small perforations in the ceiling: metal electrical boxes, drywall seams, and any place a wire or pipe comes through from below. Use expanding urethane foam to seal holes around PVC vent pipe (1), in electrical boxes (2), and especially at ceiling-corner drywall seams (3). If any of the sealing comes under local regulations for fire-stopping or draft-stopping, then use fire- or smoke-rated foam or caulking.
1
2
3
Upgrade Your Attic Insulation
51
Replace, Seal, or Enclose Recessed Lights
R
ecessed lights are one of the most overlooked sources of air leaks into attics. The best choice is to change old can bodies (1) for airtight insulation-contact-rated (IC-rated) models (see the photo at right) and then seal the rim to the drywall with foam or caulk. IC-rated lights that aren’t airtight can be sealed by covering the fixture with an airtight box made from rigid-foam insulation (2 and 3), ), metal, or drywall, or by sealing holes in the can body with spray-foam insulation (4). Remember that non-IC-rated cans need an airspace around them and can’t come in contact with the insulation. Some sources recommend installing a sealed box over non-IC-rated cans, but recessed-light manufacturers frown on this practice. The best practice is to replace non-IC-rated cans with air-sealed IC-rated models.
52
1
2
3
4
Insulation
IC-rated light. an airtight insulation-contact-rated recessed light.
Block the Biggest Offenders The attic access is a big leak that can be fixed quickly: Build or buy an insulated cover for the access bulkhead. The key is to provide a rim to connect to the sealing cover. The rim can be made from strips of sheathing, framing lumber, or rigid foam; then the cover sits on top or fits around the rim. On this job, I added a deck of leftover 1⁄ 2-in. plywood and OSB after the insulation was added. Interior soffits that are framed before the drywall is hung can leak huge quantities of air. Fill in the openings between the ceiling joists above the soffits with solid materials like rigid-foam panels, drywall pieces, or sheathing scraps, then seal the edges with expanding foam or caulk. Joist bays should be sealed with rigid blocks to keep insulation where it belongs. Cut rigid foam into strips the width of the joist bays, and slip them out over the top wall plate (photo at top right). The panels block the loosefill insulation that’s to be installed from clogging the soffit-to-ridge air channel and add a higher R-value to the short space over the plate.
layered batts can be tight together to minimize heat loss through the joists and to maximize performance. If I’m upgrading to loose-fill insulation, I keep it from falling into eave soffits and maintain channels for roof ventilation by installing a layer of blocking made from rigid insulation in the rafter (or truss) bays over the exterior-wall plates. I notch the rigid insulation around the rafters so that I get a tight fit in the bay.
Two pieces of 1-in.-thick rigid-foam insulation glued to 1⁄ 2-in. plywood
Foam weatherstripping acts as a gasket seal. OSB deck acts as rim. Ceiling joist
Ceiling joist A 2-in.-thick layer of rigid foam, sealed with caulk or expanding foam, makes an airtight soffit. Drywall Soffit
Blowing Insulation is a Two-Person Operation Blown-in loose-fill cellulose or fiberglass isn’t as common as batt insulation, but both are installed quickly and completely cover the attic floor. Loose fill can be blown in over any existing insulation that’s been tuned up first. Comparisons in R-value between the two are similar (around R-3.2 per in.). Over the first year, cellulose tends to Upgrade Your Attic Insulation
53
Blowing Insulation Is a Team Effort
A
division of labor keeps insulation flowing. One person handles the hose, and the other feeds the blowing machine. The most critical job is at the machine (see the top left photo below and the bottom right photo), where the steady rate of insulation flow is controlled by the operator. At the other end of the hose, it’s best to start at the farthest point and work back to the attic access. A slight upward hose angle helps to spread the insulation more evenly.
54
Insulation
Fiberglass made easier Owens Corning® (www.owenscorning.com) has introduced AttiCat®, a rental system that processes and distributes bales of fiberglass. The packaging is stripped as the bale is pushed into the hopper. Then the machine agitates the fiberglass and blows it out through the hose. The blowing fiberglass (top right photo below) is not as dusty as cellulose.
settle more than fiberglass. Of the two materials, cellulose is generally more available to homeowners; both can be installed with the same basic techniques. A two-person crew is the absolute minimum. The machines used to blow in insulation vary in power and features, but rental machines are typically the most basic. Pick a blower location as close to the attic access as possible. Cellulose and blowing fiberglass are messy to handle, so the loading area will be covered quickly. I prefer to set up outside, but a garage is an ideal place to stage the bales and blower when the weather doesn’t cooperate. I lay down a large, clean tarp and place the machine in the middle with the bales close by. Insulation that falls onto the tarp is easy to gather up and reload. Don’t let any debris get mixed into fallen insulation. Nails and sticks can jam the blower or plug the hose. Route the delivery hose through the shortest, straightest distance to the attic. Runs of 50 ft. or less are ideal. Runs longer than 100 ft. or runs with a lot of bends reduce airflow and can lead to a plugged hose.
Cost and Labor for an Attic Upgrade
T
he project was a 1950s ranch with 1,500 sq. ft. of attic space. Here’s a breakdown of the costs. It’s mostly labor, and relatively little money for materials.
Air-Sealing One tube of fire-barrier caulk: $7 Two cans of polyurethane foam: $20 Scrap pieces of rigid foam and recycled metal drip edge: $30 Labor: About three hours
Insulation Cellulose bales and blower rental: $500 Labor: About eight hours to tune up existing insulation. Also, two people for three hours to blow in cellulose and clean up. Optional: Seven hours to lay a new floor deck.
Total Materials: $557; optional floor deck: $170 Labor: 17 hours
All blowing machines have an agitator that breaks up the insulation bales and a blower that drives air and insulation
the ceiling causes the insulation to mound
through a hose. The person feeding the
up. If high spots occur, use a long stick or
machine breaks up the bales and drops them
broom to even them off. Although high
through a protective grate on top of a hop-
spots aren’t really a problem, low spots don’t
per. It takes a little practice to know how fast
perform as well.
and how full to feed the machine, especially
Once insulation covers the ceiling joists,
when using a basic blower. Fill too fast, and
there’s little way to know the depth of the
you run the risk of slowing the flow through
insulation. Insulation distributors sell paper
the delivery hose. After a little practice, the
gauges marked in inches that you staple to
loader understands the sounds the blower
rafters or ceiling joists. I make gauges by cut-
makes and can adjust loading speed for opti-
ting 11⁄ 2-in.-wide cardboard strips about 1 in.
mal delivery.
to 2 in. longer than the target depth; I draw
The insulation dispenser handles the hose
a line across each strip at the final insulation
and works from the far ends of the attic
grade. Expecting the insulation to settle 1 in.
toward the access hole. Good lighting is
or 2 in. over time, I mark the strips at 14 in.
a must. If hard-wired attic lighting isn’t
and staple them to the sides of the ceiling
enough, run a string of work lights or wear a
joists every 6 ft.
high-powered headlamp. Discharge the hose at a slight angle upward, and let the insulation fall into place. This helps it to spread more evenly. Shooting the hose directly at
Mike Guertin (www.mikeguertin.com) is a builder, remodeling contractor, and writer in East Greenwich, R.I.
Upgrade Your Attic Insulation
55
insulation
2
Beef Up Your Old Insulation without Tearing into Walls By Justin Fink
W
hen it comes to insulating floors,
insulation, or none at all? The ones who
walls, and ceilings, nothing makes
don’t have the luxury of gutting their walls?
it easier than working with the blank canvas
The ones who work on or live in houses that
of a newly framed house. The walls are wide
hemorrhage heat in the winter and bake like
open, so contractors can add any type of
an oven during the summer? What can we
insulation they want to achieve the best pos-
do to improve the thermal performance of
sible thermal performance.
these homes?
What about the rest of us, though? Those of us living in houses built with minimal
Balsam wool
A lot. Techniques and materials for retrofitting insulation in old walls have improved
Urea-formaldehyde foam
Vermiculite
over the years. Many times, insulation can
find that the existing insulation is
be added from the interior or exterior of the
astonishingly inferior and that a small out-
house without gutting the walls. Even so,
lay of cash would mean a significant
I’m not going to sugarcoat this: Adding new
decrease in your energy bills. Or you
insulation to closed walls is a hassle.
could be surprised to find that a high-cost retrofit will offer only a minuscule return on
Pick the Low-Hanging investment. Fruit First What’s in My Walls? Before thinking about adding insulation to
your walls, you should have already tackled your home’s other major weak spots. If you haven’t, you should, and your efforts should begin in the attic, where the most heat loss typically occurs (see “Upgrade Your Attic Insulation,” pp. 46–55). If, however, after air-sealing and insulating the attic and plugging some other common energy trouble spots (see “Home Remedies for Energy Nosebleeds,” pp. 12–19) your house still feels drafty and your energy bills are still too high, it’s time to consider the walls. There’s a lot to consider when it comes to adding new insulation to old walls. The first step is to find out what type of insulation, if any, is already in the walls. Once that is determined, you can assess the thermal performance of the walls and then make a more informed decision about the potential benefits of an insulation upgrade. You might
Fiberglass
Rock wool
The first step to determining your upgrade options is to learn the type and amount of insulation, if any, in your walls. Houses built before 1930 often were left uninsulated, so you will find either empty stud bays or insulation that was added later. Houses built in the ’40s, ’50s, and beyond typically were insulated, but often with thin batts that didn’t fill the wall cavity. The possibilities shown here represent the most common types of early insulation, but it’s not a comprehensive list. Many of the earliest forms of insulation were driven by the local industry. If the town was home to sawmills, the surrounding houses could be insulated with sawdust. If the town was an agricultural hub, rice hulls were fairly common. What you find in your walls is limited only by the whim of the builder and the previous homeowners.
Cotton batts
Beef Up Your Old Insulation without Tearing into Walls
57
BALSAM WOOL, 1940 1940s What is it? “Wool” is a bit misleading because this insulation is essentially chopped balsam wood fibers. Positive ID Although some installations may have been loose fill, this tan/brown insulation was most often packaged and installed in black-paper-faced batts. The tan fibers look similar to sawdust. Health note Balsam wool is not a health
Upgrade outlook Although it’s rated at R-4.5 per in., UFFI rarely performs at this level. This foam is well known for its high rate of shrinkage and tendency to deteriorate if in contact with water, and it also crumbles if disturbed during remodeling. The result is walls that likely have large voids, but this insulation isn’t a good candidate for discreet removal. The best option here is to add rigid foam to the exterior to help to make up for the large air voids that are likely hidden in the wall.
hazard, but take care when investigating this insulation; wear a dust mask. Because
VERMICULITE, 1925 TO 1950
the paper batts are likely to be brittle to the
What is it? This naturally occurring mineral
touch, disturbing them too much may
was heated to make it expand into
leave holes that will decrease thermal
a lightweight, fire-retardant
performance.
insulating material.
Upgrade outlook This insulation was typi-
Positive ID
cally fastened to wall studs similar to fiber-
Brownish-pink or
glass batts. Balsam wool should still yield
brownish-silver in
an R-value of between R-2 and R-3 per in.
color, these lightweight
if installed correctly, but the batts are likely
pellets were typically poured
only a couple of inches thick. Consider fill-
into closed wall cavities and into the voids
ing the remaining empty space in the stud
in masonry blocks.
cavities with blown cellulose or fiberglass. Some manufacturers of pour foam also recommend their product for this type of installation.
UREA -FORMALDEHYDE FOAM, 1950 TO 1982 (MOSTLY IN THE L ATE 1970s) What is it? Also known as UFFI, this oncepopular retrofit option is a mixture of urea, formaldehyde, and a foaming agent that were combined on site and sprayed into wall cavities. Positive ID Lightweight with brownish-gold coloring, this foam is fragile and likely to crumble if touched (hence the smooth chunks shown at left). Health note Because this open-cell foam was banned in 1982 and most of the off-gassing happened in the hours and days following installation, chances of elevated levels of formaldehyde are slim.
58
Insulation
Health note Seventy to eighty percent of vermiculite came from a mine in Libby, Mont., that was later found to contain asbestos. The mine has been closed since 1990, but the EPA suggests treating previously installed vermiculite as if it is contaminated. If undisturbed, it’s not a health risk, but if you want to upgrade to a different type of insulation, call an asbestos-removal professional. Upgrade outlook Vermiculite doesn’t typically settle and should still offer its original R-value of between R-2 and R-2.5 per in. This low thermal performance makes it an attractive candidate for upgrade, especially because it’s a cinch to remove: Cut a hole, and it pours right out. But the potential for asbestos contamination makes the prep work and personal protection more of a hassle, and the job more costly as a result.
If cavities are not filled to the top, consider
Health note Research indicates that this is
topping them off; fiberglass, cellulose, or
a safe material. It’s still in use today, and it’s
pour foam will work if there is access from
gaining popularity among green builders.
the attic.
Upgrade outlook Rock wool is fairly dense,
FIBERGL ASS, L ATE 1930 1930s TO PRESENT What is it? This manmade product consists of fine strands of glass grouped together in a thick blanket. Positive ID Most
so it’s less likely than other materials to have settled over time. If installed correctly, it should still yield a value of R-3 to R-4 per in., about the same as blown fiberglass or cellulose insulation. If anything, consider adding housewrap or a thin layer of rigid foam to the outside of the wall to air-seal the structure. If more insulation is desired, go with rigid foam.
often yellow, though pink, white, blue, and green types are used. Older products were typically paper-faced batts. Health note Official health information on fiberglass is ambiguous; the argument over whether it’s a carcinogen continues. Even if it’s not a cancer-causing material, it will make you itchy and irritate your lungs if disturbed. Be on the safe side if you plan to remove this insulation; wear gloves, long sleeves, goggles, and a respirator. Upgrade outlook Fiberglass has a decent thermal performance of between R-3 and R-4.5 per in., but early products were typically only about 2 in. thick. Consider filling the remaining empty space in the stud cavities with blown cellulose or blown fiberglass. Some manufacturers of pour foam also recommend their product for this type of installation.
ROCK WOOL (MOSTLY IN THE 1950s) What is it? Rock wool is a specific type of mineral wool, a by-product of the oresmelting process. Positive ID This fluffy, cottonlike material was typically installed as loose fill or batts. It usually started out white or gray, but even the white version will likely be blackened or brown from decades of filtering dirt out of air flowing through the cavity.
How to Find Out Electrical outlets You often can get a peek at what’s in walls by removing electrical-outlet coverplates and shining a flashlight into the space where the drywall or plaster meets the electrical box.
look up or Down Drilling a hole up into the wall cavity from the basement or down through the top plate from the attic may be helpful. A piece of wire bent into a hook is a helpful probing tool.
Cut a small Hole This last resort should be done in a location that will go unnoticed once patched up. Cut a neat hole with a drywall saw—a small square or rectangle will be easiest to replace—and keep the piece to use later as a patch.
Beef Up Your Old Insulation without Tearing into Walls
59
Out with the Old
COTTON BATTS, 1935 TO 1950 What is it? Made of a naturally grown material, cotton batts
i
f your walls are filled with old insulation and your remodeling plans don’t involve gutting the house, then you can either add rigid insulation to the exterior of the house (see the sidebar on the facing page) or, in some cases, surgically remove the old insulation. Vermiculite can be removed by drilling a hole through the wall at the bottom of the stud cavity and letting gravity empty the stud bays. In balloon-framed houses, which have wall studs that run continuously from the foundation to the roofline, blocking in the basement can be removed to access the stud cavities above. Batts or dense fibrous insulations can be removed by cutting a “bellyband,” in which a narrow strip of wall is removed about 4 ft. from the floor (this can be done from the exterior as well). With this strip of wall open, the batts can be pulled out—a homemade hook helps—and new insulation can be blown or poured into the cavities through the same openings before they are patched.
are treated to be flame resistant. Positive ID This white insulation is dense, but still fluffy. It’s not as refined as cotton balls; instead, it’s likely to have more of a pilly, fuzzy appearance. Although several companies manufactured cotton batts, one of the most popular seems to have been Lockport Cotton Batting. Look for a product name (Lo-K) and company logo on the batts’ paper facing. Health note Cotton is all natural and is perfectly safe to touch, but don’t remove the batts or otherwise disturb the insulation without wearing at least a nuisance dust mask or respirator to protect your lungs. Also, cotton by nature is absorbent, so if it gets wet, it will take time to dry. Upgrade outlook The growing popularity of green-building materials has sparked renewed interest in cotton batts. Although these modern versions of cotton batting, often referred to as “blue-jean insulation,” have an R-value of R-3.5 to R-4 per in., there is some controversy over the R-value of the old versions. Some sources claim the old products perform similarly to the modern versions, and others estimate the R-value to be as low as R-0.5 per in. Considering the density of the old cotton batts, such a low R-value seems unlikely. Justin Fink is a senior editor of Fine Homebuilding.
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Insulation
Upgrade Options: Foam Rigid Foam Always Works
i
t doesn’t matter how the walls were built, what type of insulation they have now, or how many obstructions are hidden in the wall cavities: Rigidfoam panels installed over the exterior side of the walls are always an option. However, installation is not as easy as cutting the lightweight panels with a utility knife and nailing them to the framing, though that’s part of it. Rigid foam must be applied directly to the framing or sheathing, or on top of the existing siding, then covered with new siding. In any case, you are faced with a full re-siding job and maybe a siding tearoff. Also, depending on the added thickness of the panels, windows and doors might need to be furred out, and roof rakes and eaves extended. As long as the installation is detailed carefully, though, the result is wall cavities that stay warm and dry, allowing your existing insulation to perform its best. Panels are available in 2-ft. by 8-ft. or 4-ft. by 8-ft. sheets, and range from 1⁄ 2 in. to 2 in. in thickness. Vapor permeability is determined by the type of foam and the presence of a facing. Panels faced with foil or plastic are class-I vapor retarders (also called vapor barriers) and should not be used if the house has poly sheeting or an equivalent vapor retarder under the drywall. Unfaced or fiberglass-faced panels allow water vapor to pass and won’t be problematic in combination with a class-I retarder.
EPS is unfaced, which makes it more fragile to handle but also allows the passage of water vapor. Unfaced EPS should be installed in combination with #15 felt paper or housewrap. EXtRuDED PolystyREnE (XPs) XPS falls in the middle of the three types of rigid-foam insulation in terms of cost and performance. Easy to spot by its blue, pink, or green color, XPS is slightly more expensive than EPS (50¢ per sq. ft. for 1-in. thickness) and also offers better performance (about R-5 per in.). Panels are commonly unfaced, and though water-vapor transmission slows on thicker panels, all XPS panels greater than 1 in. thick are considered class-II vapor retarders, which allow water vapor to pass. PolyisoCyanuRatE (Polyiso) This is the most expensive type of rigid foam (about 80¢ per sq. ft. for 1-in. thickness), but also the best insulator (about R-6.5). Polyiso is a popular choice for retrofit applications because it packs more insulation into a thin package—less hassle for detailing windows and doors. All polyiso boards are faced, most with foil, which retards the flow of water vapor. souRCEs
EXPanDED PolystyREnE (EPs) These white, closed-cell panels are made from the same polystyrene beads used in disposable coffee cups. EPS is the least expensive option (45¢ per sq. ft. for 1-in. thickness) and has the lowest R-value of the group (about R-4 per in.). Some
www.owenscorning.com www.polarcentral.com www.styrofoam.com
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61
Upgrade Options: Foam continued Pour Foam Is the Most Thorough
t
his water- or HFC- (hydrofluorocarbon) blown mixture is injected into the wall cavity from either the interior or the exterior through two or more 3⁄4-in.- to 1-in.-dia. holes. The foam flows to the bottom of the stud cavity, where it slowly expands upward, surrounding even the most complicated plumbing and electrical obstructions, and filling every gap to create an airtight wall assembly. Pour foam follows the path of least resistance as it expands, so the bottoms of stud cavities (in the basement or crawlspace) need to be sealed in balloon-framed houses. Old houses with siding installed directly over the studs will likely have foam squeeze-out between siding courses, which must be removed with a paint scraper once cured. Blowouts or distortions in drywall, plaster, or siding are also possible, although this is typically not a concern if the foam is installed by trained professionals. Still, this is the reason why most pour-foam companies don’t sell directly to the public, instead relying on a network of trained installers. Tiger Foam®, on the other hand, sells disposable do-ityourself kits to homeowners.
Rigid foam
Pour foam
Although there are videos on the Internet showing pour foam being injected into wall cavities that have fiberglass insulation—compressing the batts against the wallboard or sheathing—most manufacturers do not recommend this practice. The pour foam could bond to individual strands of fiberglass and tear it apart as it expands, creating voids. Tiger Foam is the exception, but the company recommends the use of a long fill tube to control the injection. Installation from the exterior requires removal of some clapboards or shingles. Installation from the inside is easier, but requires more prep work (moving furniture, wall art, drapes, etc.). Homeowners can expect a slight odor after installation and for the day following; proper ventilation is a must. Homeowners can plan to spend from $2 to $6 per sq. ft. of wall area for a professional installation, depending on job specifics and foam choice. Tiger Foam’s do-it-yourself kits sell for about $4 to $7 per sq. ft., depending on quantity. Open-cell foams—which are more permeable to water-vapor transmission—are about R-4 per in.; closed-cell, around R-6 per in. souRCEs
www.demilecusa.com www.fomo.com www.icynene.com www.polymaster.com www.tigerfoam.com
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Insulation
Upgrade Options: Blown-In The Most Common Approach
Cellulose
his method begins with compressed packs of dry cellulose or fiberglass, which are dumped into the hopper of a blowing machine, where they are agitated and loosened. A 1-in.- to 2-in.-dia. hose runs from the blowing machine through a hole in the interior or exterior side of the wall and is lowered to the bottom of the stud cavity. The installation process usually involves either one hole at the top of each cavity and a long fill tube that is withdrawn as the insulation fills the space, or a “double-blow” method, where two holes are used—one about 4 ft. from the floor and a second near the top of the wall. Both cellulose and fiberglass do a good job of surrounding typical plumbing and electrical utilities routed through the wall, but the finished density of the insulation is crucial. Cellulose that’s installed too loosely will settle and create voids in the wall, and fiberglass that’s packed too densely will not offer the performance you paid for.
This insulation is made from 80% post-consumer recycled newspaper and is treated with nontoxic borates to resist fire and mold. It’s a good choice because of its balance among cost, thermal performance, and environmentally friendly characteristics. Also, unlike fiberglass insulation, cellulose doesn’t rely only on its ability to trap air to stop heat flow. Cellulose can be packed tightly into a wall cavity to resist airflow—a practice called “dense-packing”— yielding an R-value of R-3 to R-4 per in. Although blowing loose-fill cellulose into attics is a pretty straightforward process (and is touted as a good do-it-yourself project), dense-packing is more complicated. As the material is blown into the cavity, the blowing machine bogs down, letting the installer know to pull back the hose a bit. This process repeats until the wall is packed full of cellulose. Although it is possible to pack cellulose too densely, the more common problem is not packing it densely enough. Most blowing machines that are available as rentals are designed for blowing loose cellulose in an open attic. These machines aren’t powerful enough to pack cellulose into a wall cavity, and unpacked cellulose can settle and leave voids. The Cellulose Insulation Manufacturers Association (www.cellulose.org) recommends that dense-pack cellulose be installed only by trained professionals with more powerful blowing machines. Material prices are about 25¢ per sq. ft. of wall space. Finally, if soaked with water, cellulose is likely to settle, leaving voids. Then again, if there’s liquid water in the wall cavity, voids in the insulation will be the least of your worries, and the least of your expenses.
t
Cellulose
Beef Up Your Old Insulation without Tearing into Walls
63
Upgrade Options: Blown-In continued Fiberglass
Fiberglass This loose-fill insulation is made from molten glass that is spun into loose fibers. The material is available in two forms, either as a by-product of manufacturing traditional fiberglass batts and rolls, or from “prime” fibers produced especially for blowing applications. In either case, the material is noncombustible, will not absorb water, and is inorganic, so it will not support mold growth. Fiberglass resists heat flow by trapping pockets of air between fibers, so the insulation must be left fluffy to take advantage of the air-trapping nature of the material. The R-value (typically between R-2.5 and R-4) is dependent not only on the thickness of the wall cavity but also on the density at which the insulation is installed. For information on ensuring that the fiberglass is installed to provide the stated R-value, visit the North American Insulation Manufacturer’s Association (www.naima.org) for a free overview.
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Insulation
Because fiberglass doesn’t need to be blown to such high densities, it’s a more user-friendly installation for nonprofessionals. On the other hand, loose fiberglass is not as readily available as cellulose, which is often a stock item at home-improvement centers. Finally, fiberglass advocates contend that their product won’t absorb water and that cellulose will—though fiberglass will still sag if it becomes wet. Material prices are about 45¢ per sq. ft. of wall space. souRCEs
www.certainteed.com www.greenfiber.com www.johnsmanville.com www.knaufusa.com www.owenscorning.com
All You Need to Know about Spray Foam By Rob Yagid
I
recently spent a day pulling wire with a
barrier and significantly reduces energy loss.
friend who’s an electrician in New York.
Combined with a higher R-value than most
Late in the afternoon, our conversation
other forms of insulation, it’s no wonder
turned to a client and friend of his who
spray foam is often relied on to help make
was seeking advice about insulating her
houses ultraefficient. Choosing to insulate
new home. The topic caught the interest of
your home with spray foam doesn’t guar-
some other guys on site, most from differ-
antee that it’ll perform to its full potential.
ent trades, who gathered around and offered
Different climates, construction practices,
their opinions on which material she should
and wall and roof assemblies benefit from
use. After a brief debate, everyone seemed
different types of foam. The installation of
confident that spray foam would yield the
foam at specific thicknesses is critical when
best performance. That was until I threw out
you’re trying to get the most performance
the question, “Which type?” Sure, they all
for the money.
knew there were two types of spray polyurethane foam, open cell and closed cell, but no one knew enough about them to step up and defend the use of one over the other. The truth is, neither did I. Spray polyurethane-foam manufacturers have a relatively easy job when it comes to marketing their products because of one key statistic. According to the U.S. Department of Energy, 30% or more of a home’s heating and cooling costs are attributed to air leakage. Spray polyurethane foam, or spray foam as it’s most often called, is an effective air
It Won’t Settle, and It Doesn’t OffGas Toxic Chemicals Because of the urea-formaldehyde foam used to insulate homes in the 1970s, which could degrade and off-gas unsafe formaldehyde, spray foam is often perceived as being unhealthful and poorly performing. Installers that look as if they’re outfitted to survive a
Insulation
2
CLOSED CELL Density: 2 lb. per cu. ft. R-value: 6 per in. (aged) Vapor permeability: Semi-impermeable Air barrier: Yes Blowing agent: Hydrofluorocarbon
nuclear catastrophe perpetuate the miscon-
To get the full
ception that spray foam is toxic. The fact is that when it’s installed prop-
The Open-Cell vs. Closed-Cell Debate
benefit of this
erly, spray foam is more physically stable
superinsulation,
In most closed-cell foams, such as those
than the studs and sheathing it’s adhered to.
made by Corbond®, an HFC blowing agent
you must
The oxygen-supplied respirators and head-
is captured in the foam’s cell structure. This
to-toe protective suits installers wear are
gas has a better thermal performance than
necessary only to keep the chemicals that
the air-filled open-cell foam and gives it a
make up spray foam out of their lungs and
higher overall R-value. However, while HFC-
off their skin during installation.
blown closed-cell foam might initially have
understand the difference between open- and closedcell foams, how they perform, and which to use.
The blowing agent, a gas that expands
an R-value as high as R-8 per in., its R-value
the foam’s cells to give it volume, receives
diminishes as the blowing agent evaporates
a lot of scrutiny. Over time, from three
through cell walls and is replaced by air.
months to a year, a portion of the blowing
Closed-cell foam’s “aged” R-value is roughly
agent in closed-cell foam evaporates into the
R-6 per in. Some manufacturers produce
air. Prior to 2003, chlorofluorocarbon and
water-blown closed-cell foams. These foams
hydrochlorofluorocarbon blowing agents
have the same performance properties as
were in widespread use. These gases are dam-
HFC-blown foam, but slightly lower R-values,
aging to the atmosphere. The U.S. Environ-
at around R-5.5 per in.
mental Protection Agency has banned the
Closed-cell foam’s greater density, 2 lb.
use of those chemicals and recognized the
per cu. ft. compared with open cell’s 1⁄ 2 lb.
current hydrofluorocarbon (HFC) blowing
per cu. ft., also increases its R-value and
agent as a safe alternative.
offers it the rigidity that open-cell foam
Open-cell foam, which uses water as its
lacks. Tests at the National Association of
blowing agent, emits carbon dioxide as it
Home Builders research center confirmed
expands. But manufacturers claim that the
that closed-cell foam can actually increase
amount of carbon dioxide released from the
the shear strength of conventionally framed
foam has a limited impact on the environ-
walls by 30%. Closed-cell foam also has a
ment. The Spray Polyurethane Foam Alli-
low vapor-permeability rating (roughly
ance is currently testing this issue.
0.5 perms at a thickness of 3 in.) and is considered a class-II vapor retarder, meaning it’s semi-impermeable.
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Insulation
OPEN CELL Density: 1⁄ 2 lb. per cu. ft. R-value: 3.5 per in. Vapor permeability: Permeable Air barrier: Yes Blowing agent: Water
Open-cell foam, made by companies such as Icynene® and Demilec®, has a greater expansion rate than closed-cell foam. It expands 100 times its initial volume (closedcell foam expands only 30 times its initial volume), so less of the foam is needed to insulate a house. Open cell’s one major weakness is its lower R-value, roughly R-3.5 per in. This means that when used in a 2×4 exterior wall, it will create an assembly that’s approximately only R-12, which won’t meet code in most parts of the country.
Installing Lots of Foam Isn’t as Effective as You Think A lot of energy-conscious architects and builders shoot for the highest R-values they can possibly attain: R-40 walls and an R-60 roof. However, R-values aren’t necessarily an accurate reflection of overall thermal perfor-
Proper prep yields the best installation. While spray foam is installed by a pro, it’s your responsibility to prep the site. Masking windows, electrical boxes, and even floors is important if you want the foam contained to wall, roof, and floor cavities. anyone on site during the installation should be outfitted for optimum protection.
mance. For example, you would think that an R-40 wall full of spray foam would perform twice as well as a wall sprayed to R-20 with the same foam, but that’s not the case. Chris Porter, the building-science and code manager for BioBased Insulation®, explains that “open-cell foam reaches a point of diminishing returns at around
5 in. That threshold is even lower for closedcell foam, which experiences diminishing returns at around 3 in. or 4 in.” Those thicknesses create assemblies between R-20 and R-24, which by the numbers seem a little weak. Each additional inch of spray foam
All You Need to Know about Spray Foam
67
More Than One Way to Use Spray Foam: Two Experts Weigh In Most experts agree that spray polyurethane foam is a revolutionary product. What they don’t always agree on is the way it’s installed and integrated into a building assembly. To shed some light on this debate, energy-efficient building expert Bruce Harley (Westborough, Mass.) and architect Peter Pfeiffer (Austin, Texas) explain how they use spray polyurethane foam to insulate the homes they build. R-42 ROOF 2×10 rafters BRUCE HARLEY 5 ⁄ 8-in. OSB Spray foam can be a great mate- #30 building paper under asphalt rial, but understanding its use shingles 6-in. is often hindered closed-cell foam by overeager installers who emphasize the magic rather than Mineral-wool batts the real properties of the products. 2×6 stud wall Too often, I hear 1⁄ 2-in. OSB from clients that “my dealer said that I only need 2 in. to 4 in. of 3⁄ 8-in. furring foam in my walls R-19 because it perstrips over WALLS forms just like housewrap R-40 fiberglass and prevents any possible moisture problems.” It’s just not true. An R-12 wall is an R-12 wall, no matter Fiber-cement what the matesiding rial is. Cutting air leakage saves energy, but it doesn’t Insulated rim joist make up for a low R-value. For best performance, I use spray foam in a variety Non-paper-faced of ways when dedrywall over 2×4 signing the shell stud wall of a home. Here’s one example. R-19 BASEMENT Bruce Harley of Conservation Services Group is an energy-efficient construction expert and author of Cut Your Energy Bills Now (The Taunton Press, 2008).
Damp proofing
68
Insulation
2-in. space
51⁄ 2-in. layer of open-cell foam
Concrete slab over 2-in. XPS foam
R-22 ROOF 24-ga. Galvalume® 1×4 lath creates 3⁄4-in. airspace. #30 building paper 5 ⁄ 8-in. 1-in. closedplywood cell flash coat 2×6 roof trusses
Open-cell foam Minimum 3⁄4-in. EPS foam board 2×4 stud wall R-17 WALLS 21⁄ 2-in. damp blown-in cellulose
Housewrap/ drainage plane 1⁄ 2-in. OSB or ZIP wall sheathing
3-in. closedcell foam R-18 CRAWLSPACE
15-mil vapor barrier seams taped
1-in. flash coat of closedcell foam
PETER PFEIFFER No other insulation system I am familiar with provides the real R-value that spray foam does, accomplishes the air-sealing it does, or thwarts vapor flow as well. Closed-cell spray foam greatly reduces the chance for condensation within the framing of a home. I think it is critical that houses be built to thwart vapor flow correctly. I insulate all homes pretty much the same way. However, in colder climates, I use 2×6 exterior walls and insulate the basement or crawlspace. Peter Pfeiffer of Barley & Pfeiffer Architects is a LEED-accredited architect and building scientist who has spent the past 30 years developing highperformance building-design strategies.
Fiber-cement siding Vapor barrier extends 12 in. up wall and is secured with mastic.
Spray Foam for the Eco-Conscious
Sources
C
Although this is not a complete list of sprayfoam manufacturers, it is representative of the larger national companies. For assistance in finding a spray-foam insulation contractor, visit the Spray Polyurethane Foam Alliance at www.sprayfoam.org.
onsuming fossil fuels to make products intended to conserve fossil fuels makes little sense to a lot of people. All spray foams contain a certain level of petroleum in their A component and in their B component. Manufacturers such as BioBased Insulation, Demilec, and Icynene have created more environmentally benign spray-foam products by reducing the amount of petroleum used in their B component. They replace a portion of the polyol resin, which makes up 20% to 30% of the B component, with a renewable resource such as soybean or castor-bean oil. Apex even has a sucrose-based polyol. Manufacturers say that the transition to bean oil or sucrose doesn’t alter the look or the performance of open- or closed-cell foam in any way. The amount of soybean, castor bean, or sucrose found in foam varies by manufacturer, so identifying the “greenest” foam might not be so easy. According to the U.S. Department of Agriculture, only 7% of a spray-foam product needs to be made of a renewable resource to be labeled as a biobased foam. This, of course, doesn’t factor in the petroleum fueling the crop-cultivation process.
BASF ® : www.basf.com BioBased: www.biobased.net CertainTeed ® : www.certainteed.com Chemical Design: www.chemicaldesign corp.net Corbond: www.corbond.com
Hardworking crops. The oil from soybeans, which is also being considered to create alternative forms of energy, is replacing the petroleum in some spray foams.
Demilec: www.demilecusa.com Foametix ® : www.foametix.com Fomo Products: www.fomo.com Great Stuff™: www.greatstuff.dow .com Icynene: www.icynene.com NCFI: www.ncfi.com Tiger Foam: www.tigerfoam.com Touch ‘n Seal ® : www.touch-n-seal.com
yields little performance. In fact, while the
ingly inconsistent. North Carolina builder
cost of an R-40 wall is indeed double that of
Michael Chandler recommends getting as
an R-20 wall (not factoring in the construc-
many bids as possible. “I’ve received quotes
tion materials used to create deeper cavities
from $6,800 to $13,500 for the same exact
for the extra foam), it reduces the heat flow
job,” Chandler says. “Prices vary so much
through a wall by only an additional 2%.
that it may actually pay to have a truck drive
For this reason, Porter says that in most
two hours to do the job rather than have
parts of the country, 6 in. of foam—be it
the local guy spray it.” The message: Search
open or closed cell—is perfectly adequate.
far and wide for the installer that suits your
Spray foam is priced based on board feet.
Urethane Soy Systems: www.soyol.com Versi-Foam ® Systems: www.rhhfoamsystems .com
needs and your budget.
Manufacturers don’t price their product. Instead, cost is determined by installers. The spray-foam market is extremely competi-
Rob Yagid is an associate editor at Fine Homebuilding.
tive, and spray-foam prices can be astonish-
All You Need to Know about Spray Foam
69
insulation
2
Making Sense of Housewraps BY FERNANDO PAGÉS RUIZ
W
hen I started building houses nearly
mer, are having a hard time handling this
30 years ago, we lapped lightweight
new technology.
#15 asphalt- or rosin-impregnated building
There’s plenty of confusion surrounding
paper directly over the stud framing before
weather-resistive barriers. Many home-
installing the siding. Nowadays, concerns
owners and builders don’t know which prod-
with energy-efficient construction and
uct to choose, some builders never learned
moisture infiltration have focused a great
how to install it correctly, and many have no
deal of attention and no small amount of
idea what housewrap does in the first place.
high-tech chemistry on this thin layer of
have switched to plastic-based housewraps,
What Does a Housewrap Do?
products designed to stop air infiltration and
Placed beneath the siding, housewrap is
paper. Although some builders still advocate the felt-paper barriers of yesteryear, most
wind-driven rain while allowing water vapor to evaporate—a great concept. However, like everything high-tech, new solutions come with new problems. The range of choices and the precise installation requirements of modern housewraps challenge builders with terms like spunbonded, polyolefin-based moisture, and air-infiltration fabric. Even if the technical terminology is hard to remember, learning how to install these products correctly is important. Yet a quick look around a construction site reveals that most builders, with thirty years or with three behind the ham-
a second layer of defense for your home. When installed properly, it performs three basic functions (see the drawing on the facing page). First and foremost, housewrap acts as a backup barrier that keeps water off the structural sheathing and framing. Properly installed siding is the first line of defense, but sometimes wind-driven rain and snow still find a way through. Housewrap also functions as an air barrier that stops hot- and cold-air movement through the wall cavity. As long as joints are sealed properly, housewrap is designed to cut utility costs and
increase comfort by reducing air infiltration and potential drafts.
The Three Functions of Housewrap
The real magic of housewrap lies in its third function: allowing the free passage of water vapor so that wall cavities and framing lumber can dry to the outside of the building, reducing the threat of mold and rot. Without this feature, installing housewrap would be like putting a thick raincoat over your house: great for keeping out the rain, but terrible at releasing water vapor from within. Instead, housewraps are designed to act like a Gore-Tex® jacket, allowing water vapor to pass through the building envelope in case moisture problems arise.
A Side-by-Side Comparison Is Often Pointless
1. Create a secondary weather barrier behind the siding, preventing wind-driven rain and other water from reaching the sheathing.
3
1
2. Serve as an air barrier to prevent air infiltration, helping to reduce heating and cooling costs. 3. Provide a vaporpermeable membrane that allows moisture in framing lumber or insulation to escape.
2
Nowadays, any approved weather-resistive barrier, from #15 felt to high-tech housewrap, touts the dual benefit of being a weather-resistive drainage plane that also allows the passage of water vapor. But not every product balances these two features equally. To add to this confusion, housewraps are now available in dozens of varieties, so how do you choose? Unfortunately, there’s no easy answer. The American Society for Testing and Materials (ASTM) is working to standardize the tests used to evaluate weather-resistive barriers. For now, when trying to gain code approval, manufacturers can choose from at least two dozen different tests. Even if two manufacturers choose the same test, though, there is nothing to regulate the way in which the test materials are set up. This variability makes it nearly impossible to compare one product’s performance to another’s. According to Paul Fisette, director of building materials and wood technology at the University of Massachusetts, one tested value that usually stands up to side-by-side comparison is a material’s permeance rating,
Perm Ratings Tell Part of the Story Permeance ratings, or perms, reflect the measure of a material’s ability to transfer water vapor; the higher the perm number, the more permeable the material. For instance, 6-mil polyethylene sheeting has a very low perm rating of 0.06, which means that it prevents the passage of nearly all water vapor. Current building codes require a weather-resistive barrier to match or exceed grade-D building paper, which has a perm rating of about 5.0. To meet this requirement, perm ratings for commonly available brands of housewrap range from about 5.0 for Dow®’s Weathermate™ to 58.0 for Tyvek®’s HomeWrap®. Materials with higher perm ratings speed the escape of trapped moisture. But higher ratings do not necessarily equal better housewraps, because the methods of achieving a high perm rating can be different.
but sometimes even that can be misleading.
Making Sense of Housewraps
71
For instance, some low-tech housewraps achieve their high perm ratings with mechanically punched perforations in the membrane. These perforations increase the passage of water vapor, but they also make the housewrap more susceptible to bulkwater leakage. On the other hand, more-advanced nonperforated housewraps, such as HomeWrap and R-Wrap®, offer even greater moisturevapor transmission (higher perms) than their perforated counterparts. They are also more effective at preventing the movement of bulk water.
Independent Tests Yield Clear Performance Comparisons Fisette conducted independent testing of housewrap not to establish quantifiable data that mimicked real-world performance, but rather to subject the products to a set of simple laboratory conditions to see how they compared. For more on Fisette’s testing, see www.umass.edu/bmatwt/publications. According to Fisette’s research, the best housewraps (those that resist water infiltration and also permit water vapor to evaporate) include Tyvek HomeWrap, R-Wrap by Berry Plastics™ Corporation, Typar® (manufactured in 2003 or later), and—believe it or not—traditional #15 felt paper (see the sidebar on p. 75). I prefer Tyvek, which scored well for resisting water penetration in the Massachusetts study while also having one of the industry’s highest perm ratings for watervapor diffusion. Although #15 felt paper costs less and scores well in all categories, I like housewrap products because the variety of sizes available (3-ft. to 10-ft. widths) really speeds up the installation process. Also, the compatible sealing tapes and accessories make housewrap a superior air barrier compared to felt paper.
72
Insulation
Housewrap
Choices PinkWrap® (Owens Corning)
Nonwoven
Type: Perforated, woven polyolefin Perm rating: 14.0 Notes: Translucent membrane makes it easy to see where to nail siding. 800-438-7465; www.pinkwrap.com
Woven
HomeWrap (DuPont™) Type: Nonwoven polyolefin Perm rating: 58.0 Notes: The first housewrap on the market more than 30 years ago; accounts for 70% of total housewrap sales; highest perm rating. 800-448-9835; www.tyvek.com
StuccoWrap® (DuPont) Type: Nonwoven polyolefin Perm rating: 50.0 Notes: Designed specifically for use under traditionaland synthetic-stucco applications; helps to reduce cracking because it won’t absorb water or expand and contract. Surface texture channels water. www.tyvek.com
typar (Fiberweb®) Type: Nonwoven polyolefin Perm rating: 11.7 Notes: Excellent protection against surfactants, making it ideal for use under stucco or cedar siding; guaranteed to be tear-resistant. 800-284-2780; www.typarhousewrap.com
Making Sense of Housewraps
73
Siding Often Determines the Type of Housewrap
In these cases, it’s a good idea to choose a furrowed rain-screen housewrap. Its embossed texture provides just enough airspace for liquid water to drain away before it has a chance to penetrate the membrane
When you’re using vinyl siding, which comes with built-in drainage holes and fits on the wall loosely, an ordinary smoothfaced housewrap provides good drainage. But with tightly fastened board siding, any water trapped between the siding and a smooth housewrap will sit and eventually could make its way through the housewrap and into the framing. Remember, although many housewraps are good at resisting
(see “Rain screen and housewrap combined,” p. 76). When applying stucco, choose a housewrap designed specifically for stucco and masonry, such as DuPont’s StuccoWrap or Benjamin Obdyke’s Mortairvent®, which not only provide a corrugated surface but also are compatible with the chemicals in stucco.
bulk water, they should not be considered waterproof.
Housewrap Choices continued Perforated
Weathermate Plus (Dow) Type: Nonwoven polyolefin Perm rating: 6.7 Notes: Membrane has a more substantial, foamlike texture compared to other housewraps. 866-583-2583; www.dow.com/styrofoam
74
Insulation
Weathermate (Dow) Type: Perforated, woven polyolefin Perm rating: >5.0 Notes: Translucent; perforated products are less resistant to water intrusion; does not meet the air-barrier requirement of the National Building Code of Canada. 866-583-2583; www.dow.com/styrofoam
Barricade® (Berry Plastics Corporation) Type: Perforated, woven polyolefin Perm rating: 9.0 Notes: Translucent; perforated products are less resistant to water intrusion; resists UVdegradation for 12 months. 877-832-0333; www.berryplastics.com
I Still Prefer Felt Paper
B
ased on my lab testing at the University of Massachusetts, if I were buying housewrap today, I likely would choose a nonperforated product because it displays the best water resistance. As it happens, I have felt paper on my own home. If I could do it over again and choose between felt and housewrap, I’d still choose felt. That’s because I believe that under certain circumstances, felt paper outperforms housewrap. For example, an ice dam or a roof leak might allow liquid water to get behind the
R-Wrap (Berry Plastics Corporation) Type: Nonwoven polyolefin Perm rating: 56.0 Notes: Membrane can be installed with printed logo in or out without change in performance; manufacturer will replace product if damaged by wind. 877-832-0333; www.berryplastics.com
felt or housewrap. It’s also possible for the sun’s heat to drive water vapor through the housewrap from the outside, where it can condense on the sheathing. In either case, you have liquid water on the wrong side of the wrap. Under these conditions, the liquid water is trapped by the housewrap, which is permeable only to diffusion of water vapor. Felt, on the other hand, absorbs water and dries more quickly to the outside. Paul Fisette is director of building materials and wood technology at the University of Massachusetts.
GreenGuard® Value (Pactiv® Corporation)
GreenGuard Classic (Pactiv Corporation)
GreenGuard Ultra (Pactiv Corporation)
Type: Perforated, woven polyolefin Perm rating: 15.0 Notes: Low-cost housewrap for the valueconscious builder. Resists UV-degradation for 12 months; translucent membrane makes it easy to see where to nail siding. 800-241-4402; www.green-guard.com
Type: Perforated, woven polyolefin Perm rating: 15.0 Notes: Resists UVdegradation for 12 months. Highly tearresistant; translucent, glare-reducing green color. 800-241-4402; www.green-guard.com
Type: Nonwoven polyolefin Perm rating: 48.0 Notes: Uses a reinforcing scrim that makes it highly tear-resistant. Translucent membrane makes it easy to see where to nail siding. 800-241-4402; www.green-guard.com
Making Sense of Housewraps
75
Housewraps Are Susceptible to Certain Chemicals
limited study, Fisette found that the newest version of Typar had superior resistance to surfactants compared to the performance of similar products.
Builders have debated the chemical compatibility of housewrap for years. Studies have found that certain types of wood siding,
water resistance of housewrap also can be compromised by soaps, power-washing
like cedar and redwood, leach surfactants (surface-active contaminants) that can affect the water resistance of housewraps. The surfactants reduce the surface tension of water, easing its ability to pass through microscopic openings in the membrane. To combat the problem, manufacturers recommend back-priming potentially troublesome wood siding with a water-repellent primer. In a
In addition to the water-soluble extractives found in wood siding, the
chemicals, and even some types of latex paints. The perforated variety is most susceptible, so consider choosing a highquality, nonperforated housewrap. It’s also important not to leave housewrap exposed for longer than necessary. Housewrap left uncovered for longer than its intended UV-rating will deteriorate and decline in performance, and should be
Housewrap Choices continued Rain screen and housewrap combined
N
o matter how tight the joints, how thorough the flashing installation, or how far the roof overhangs the walls, water always finds a way behind the siding of a house. Housewrap or felt paper is a good safeguard for protecting sheathing and framing, but many builders also add a 1⁄4-in. to 3⁄ 8-in. drainage plane between the housewrap and the siding by tacking up vertical furring strips. This vented space allows moisture to dissipate naturally so that paint won’t peel prematurely, surfactants from the siding won’t be in contact with the housewrap, and bulk water won’t be trapped behind the siding with nowhere to drain. Several manufacturers have started combining the water-shedding benefits of rain-screen-wall construction with the ease of installation and the added benefits found in typical housewrap, creating a separate category sometimes referred to as “drainscreen.” To the right are a few different designs that aim to accomplish the same basic task.
76
Insulation
DrainWrap™ (DuPont) Type: Nonwoven polyolefin Perm rating: 50.0 Notes: Uses accordion-style vertical grooves to channel water. Because the product behaves like wrinkly housewrap, it isn’t as rigid as other rainscreen products. 800-448-9835; www.tyvek.com
covered with a fresh layer before siding is
works. Detailed installation instructions can
installed.
be found on manufacturers’ websites and often at the lumberyard or home center
Weatherproofing Comes with Workmanship
where housewrap is purchased.
Here’s the bottom line: Installation is more
the face of the wall, and as long as all the
important than material choice. No matter what brand of housewrap you choose, you will be wasting money unless the stuff is installed carefully. Poorly installed housewrap will cause more problems than it solves. Getting the installation right is not hard, but it requires a basic understanding of how housewrap
The basic installation premise is to think like a raindrop. Imagine a drop of water hitting the side of your house at the top of the wall. Gravity pulls the drop down along courses, joints, tears, and penetrations are sealed and lapped in shingle fashion, the drop eventually will reach the ground. The moment that raindrop finds a puncture, a reverse lap, or an unflashed component, it will seep behind the housewrap and into the framing.
Weather trek® (Berry Plastics Corporation)
GreenGuard Raindrop® (Pactiv Corporation)
Type: Perforated polyethylene Perm rating: 6.5 Notes: A clever nondirectional surface pattern (reminiscent of the texture of a basketball) ensures that water drains easily, regardless of orientation to the sheathing. 877-832-0333; www.berryplastics.com
Type: Woven polyolefin Perm rating: 10.0 Notes: Relies on drainage channels woven into the surface to direct water down and out. Channels must run vertically to be effective. 800-241-4402; www.green-guard.com
Home Slicker® (Benjamin Obdyke) This bound-nylon three-dimensional meshlike rain screen physically separates the housewrap and the siding. Three different versions are available (above, left to right): Home Slicker, Home Slicker Plus Typar (polyolefin housewrap), and Mortairvent (polypropylene matrix for masonry and stucco). 800-346-7655; www.benjaminobdyke.com
Making Sense of Housewraps
77
Seam Tape and Fasteners Are Vital to the System
I
t never ceases to amaze me how many builders omit seam tape from housewrap installations. Although proper lapping is enough to create a watershed, all seams must be sealed to stop air infiltration. Taping the seams also helps to preserve the housewrap’s integrity throughout construction and makes the membrane less likely to catch the wind and tear. Seam tape also provides a means to repair cuts, but every cut or penetration should always be treated like a horizontal or vertical seam. Seam tape is never used to make up for improper lapping. In fact, assume that the tape adhesive will fail eventually, allowing water to penetrate the drainage plane and wet the framing. In contrast, a proper lap can last forever. Almost every housewrap manufacturer provides a seam tape for their product. Generic building tapes such as duct tape should be avoided because they might fail sooner. Housewrap can be attached with plastic cap nails (see the photo, near right), 1-in.-wide crown staples, or large-head roofing nails. Many builders use a hammer tacker to fasten the wrap with staples, but this type of fastener is much more likely to pull through the housewrap before the siding is installed. For a better installation, manufacturers recommend the use of plastic cap nails or cap screws, which are available for manual fastening or collated for use in pneumatic nailers (see the photo, far right). Cap nails also act as a gasket to keep water from leaking through the nail holes. Whatever fastener is used, the manufacturer’s recommendations for spacing are important. The most common spacing is 8 in. to 18 in. vertically, and 16 in. to 24 in. horizontally. Fasteners should be driven into studs or sheathing such as plywood or OSB.
Hitachi NV50AP3 800-706-7337; www.hitachipowertools.com Cost: $400
Bostitch N66BC-1 800-556-6696; www.bostitch.com Cost: $320
Housewrap installation starts from the
Housewrap should always be installed
bottom and works its way up. All horizontal
with the same care and attention devoted to
joints should overlap at least 6 in., and all
siding. Although no one will see good work
vertical joints 12 in. If housewrap is applied
underneath the siding, correctly installed
to the sheathing before the wall is raised,
housewrap still pays off in the long run.
there needs to be enough material left to cover the band joist. Horizontal laps are as important as vertical laps because windblown rain can travel sideways.
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Insulation
Fernando Pagés Ruiz operates Brighton Construction Co. in Lincoln, Neb. He is also the author of Building an Affordable House: Trade Secrets for High-Value, Low-Cost Construction (The Taunton Press, 2005).
Using Rigid Foam for an Efficient and Dry House by Martin Holladay
R
emodelers who open up fiberglass-
roofs, though they do not perform equally.
insulated walls in the middle of the
EPS is the most vapor permeable of the three
winter are often surprised to see a thin
types; at R-4, it also has the lowest R-value
layer of frost on the interior side of the wall
per inch. Foil-faced polyiso is the least va-
sheathing. The frost indicates that warm,
por permeable and has the highest R-value
humid interior air is leaking through the
per inch, at R-6.5. XPS (R-5 per in.) and the
wall penetrations, leading to condensation
denser types of EPS can extend below grade,
on the cold surface of the sheathing.
but polyiso absorbs water and therefore
One way to limit this phenomenon is to
should not be installed in contact with soil.
keep the sheathing warm by adding a layer
Every wall needs a water-resistive barrier
of rigid-foam insulation on the exterior side
such as asphalt felt or housewrap. It’s also
of the sheathing. If there are no cold sur-
possible to use rigid foam as a barrier, as
faces in the wall cavities, condensation is
long as foam seams are sealed with a suitable
unlikely. A layer of exterior foam also makes
tape or installed with Z-flashing. Regardless
a house more energy efficient by increasing
of your choice of barrier, all penetrations,
insulating performance, reducing thermal
including windows and doors, need to be
bridging, and minimizing air leakage.
flashed properly; these flashings need to be
All three types of rigid-foam insulation— expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate—are suitable for use on the exterior of walls and
integrated with the barrier using adequate overlaps or durable tapes.
insulation
2
Increase Insulation and Prevent Condensation The benefits of adding a layer of rigid-foam insulation to the exterior of walls and roofs are twofold. First, the foam will increase thermal performance by adding R-value and minimizing thermal bridging. Second, the foam will keep the sheathing warm, so moisture passing through the wall or roof will find no cold surfaces for condensation to occur. For this reason, the roof does not need to be vented. That’s why exterior roof foam makes a lot of sense on difficult-to-vent hipped roofs or on roofs with multiple dormers.
Roof underlayment Asphalt shingles Peel-and-stick roof membrane 1⁄ 2-in.
roof sheathing
Two layers of 11⁄ 2-in. rigid-foam insulation Cavity insulation between rafters 5 ⁄ 8-in.
roof sheathing
Expanding spray foam
Ceiling joist
11⁄ 2-in. rigid-foam insulation between rafters and sealed in place with expanding spray foam Continuous bead of caulk
Cavity insulation between studs
11⁄ 2-in. rigid-foam insulation as sheathing
Note: If you are using asphalt shingles, make sure the manufacturer will honor the warranty if shingles are installed on unvented roofs.
Exterior Foam Is a Good Option Adding exterior foam to walls works well for new construction. As long as you meet local wind and earthquake codes, it’s usually possible to build a foam-sheathed wall without structural oriented strand board (OSB) or
•D iagonal 1×4 let-in braces. •D iagonal T-profile steel strapping, such as Simpson TWB. • I nset shear panels. •A few strategically placed pieces of OSB (they are usually installed at corners). Of course, you should check with an
plywood sheathing. Foam-sheathed walls are
engineer and your local building official
braced using one of four methods:
before finalizing your wall-bracing plan. Exterior foam sheathing is often installed on existing homes as an energy-saving
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Insulation
retrofit when new roofing or siding is need-
will reduce the chance that moisture will
ed. You can install rigid foam on the inside
accumulate in a wall. By warming the wall
of a wall as well, but adding exterior foam
cavity, exterior foam eliminates cold surfaces
increases the R-value of a wall or roof with-
where moisture can condense. Here are the
out eating up interior living space.
minimum R-values for exterior foam for
Installed on the roof, exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams. The illustration on the facing page shows
2×6 walls: • R-15 in climate zones 7 and 8 • R-11.25 in climate zone 6
two layers of OSB or plywood roof sheath-
• R-7.5 in climate zone 5
ing: a lower layer conventionally nailed to
• R-3.75 in climate zone 4
the rafters and an upper layer installed as a nailing surface for the roofing material on top of the rigid foam. The type of fasteners used and the way they need to be spaced for the top layer of sheathing depend on the pitch of the roof and roof loads, particularly wind and snow loads. It’s fairly easy to find screws with a pullout-resistance rating exceeding 400 lb., even when they are secured just to plywood or OSB sheathing. The fastener rating increases if the screws are driven into the rafters. (Fastener sources include Wind-lock® and FastenMaster®, which manufactures HeadLok® and OlyLog® screws.) Most foam-sheathed walls include a rainscreen gap between the foam and the siding. After the foam is tacked in place temporarily with a few nails, it is secured in place with vertical 1×3 or 1×4 strapping that is screwed through the foam to the underlying studs. Some siding types, including cedar shingles, may require a drainage mat, kerfed horizontal furring, or an OSB or plywood nailer over the foam.
Does Exterior Foam Create a Wrong-Side Vapor Barrier? Some builders worry that exterior foam sheathing is a “wrong-side vapor barrier” that can trap moisture in walls. In new construction without interior polyethylene
When exterior rigid foam is used as an energy-saving detail in warmer climates, condensation is not a concern, so no minimum R-values apply. Since exterior foam reduces a wall’s ability to dry to the exterior, foam-sheathed walls should be able to dry to the interior. That means that foam-sheathed walls should never include interior polyethylene or vinyl wallpaper. Painted drywall has a high enough permeance to allow any incidental moisture that enters a wall cavity in the winter to evaporate through the drywall during the summer. If you are considering installing exterior foam on a house with interior 6-mil polyethylene, proceed with caution. If water ever enters a wall with foam sheathing and interior poly, the wall has a very limited ability to dry. This raises the stakes, and watermanagement details must be impeccable. After all the siding has been removed, inspect the existing wall sheathing for stains or moisture damage. If you find either, you’ll need to diagnose the cause and implement remedies. If the existing sheathing is clean, dry, and sound, it’s safe to install exterior wall foam, as long as the new siding is installed with a rain-screen gap and meticulous flashing. Martin Holladay is a contributing editor to Fine Homebuilding.
vapor barriers, the worry is baseless. As long as the foam sheathing is thick enough, it
Using Rigid Foam for an Ef ficient and Dr y House
81
INSULATION
2
Basement Insulation Retrofits BY DANIEL S. MORRISON
F
inished basements are a great way to add living space to a house without
adding on. You often can add almost as much living space as the main floor offers. Before thinking about flooring choices and paint colors, though, think about the basics. Moisture, insulation, and air infiltration must be tackled before any finish materials are installed. In new construction, these issues are addressed from the outside before the basement is backfilled. Retrofits mean that you have to work from the inside. In either case, it is important to consider the climate before work begins.
Start with Water Management Because basements are mostly buried in the ground, they are sometimes wet, are usually
a tighter basement is less able
r-VALUe mINImUmS BY CoDe AND CLImAte ZoNe Climate zones 6, 7: R-15 Climate zones 4, 5: R-10 Climate zone 2, 3: R-5
to dry out when it becomes wet. You can use grading to manage bulk groundwater on the outside, but foundations also have to disrupt capillarity. Water in the soil can and will wick up to the roof framing if you let it. Capillary breaks such as brush-on damp-proofing, sill sealer, and rigid insulation block this process.
ing a basement to living space, the basement
Air-Sealing Saves Energy and Stops Moisture
must manage moisture better than it did
The connection between concrete founda-
before the insulating and air-sealing, because
tions and wood framing is almost always
damp, and are seldom dry. Rarely do old houses have perimeter-drainage systems, insulation, or capillary breaks. When convert-
Insulation Amount Depends on Location The International Residential Code (IRC) specifies particular R-values for each climate zone; how you get there is up to you. For very cold climates, you may need to add extra thick rigid insulation or fill the stud cavities. Don’t, however, treat a below-grade wall like a regular wall. Expect bulk-water problems, and choose insulation that can handle it. Never include a plastic vapor barrier when insulating a basement wall, because it will trap moisture. The connection between foundation, floor, and wall requires gaskets, sealants, Cold or HOT or and caulk to prevent mixed mixed air leaks. climate climate
Existing floor assembly
At least 2-in. rigid insulation Existing concrete foundation wall 2×4 stud wall 24 in. on center Optional cavity insulation
1⁄ 2-in. non-paperfaced drywall
Treated 2×4 bottom plate Sill sealer
Optional cavity insulation: For below-grade stud cavities, closedcell spray foam is best. Mineral wool or fiberglass batts are better than cellulose, which is more easily damaged by moisture.
Spray foam is best for sealing rim joists.
1-in. rigid insulation
Slope ground away from foundation.
1⁄ 2-in. nonpaper-faced drywall
The sill sealer is a capillary break.
Treated 2×4 bottom plate
Existing concrete slab
You can’t count on a footing drain to exist (or work properly) in an old house, so use grading to push away bulk water.
leaky because wood is often warped and
nections. The easiest way to seal and
concrete is rarely flat. Air leaks waste energy
insulate the rim-joist area is with spray
and cause moisture problems. Most base-
foam, but blocks of rigid foam sealed in
ment air leaks occur between the top of the
place can work well, too.
concrete wall and the bottom of the subfloor, where there are many joints and con-
Basement Insulation Retrofits
83
Which rigid Insulation Should I Use? Expanded polystyrene
Extruded polystyrene
The least-expensive choice, EPS is manufactured in different densities. EPS (typically white in color) is not as strong as XPS, and it’s susceptible to crumbling at the edges. EPS is the most vapor-permeable type of rigid foam. r-value: About 4 per in. Perm rating: 2.0 to 5.8 for 1 in., depending on density
Because of its high strength and low permeance, XPS (often blue or pink in color) is the most commonly used type of rigid foam for basement walls. r-value: About 5.0 per in. Perm rating: 0.4 to 1.6 for 1 in., depending on density
Polyisocyanurate
Mineral wool
Polyiso has a higher R-value per inch than EPS or XPS. Many building officials allow foil-faced polyiso to be installed in basements without any protective drywall, making polyiso the preferred foam for basements without stud walls. r-value: Up to 6.5 per in. Perm rating: 0.03 for 1 in. (with foil facing)
Although many energy experts advise against using fibrous materials to insulate basement walls, some builders may want to consider using mineral-wool batts because they are less susceptible to water damage. Manufacturers include Thermafiber® and Roxul®. r-value: 3.7 per in. Perm rating: Hasn’t been tested, but highly permeable
Insulation: More Is Better Rigid-foam insulation in a basement elimi-
possible to meet code minimums with rigid
nates condensation by keeping the interior
foam alone, you also can use a combination
surface of the foundation warm. How much
of rigid foam and cavity insulation.
insulation you need depends on your climate zone, though energy-conscious builders strive to exceed code minimums. While it’s
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Insulation
Daniel S. Morrison is managing editor of GreenBuildingAdvisor.com.
insulation
2
Weatherstripping By Matthew Teague
Many types of weatherstripping are available at your local home center or hardware store. You can install several products easily without specialized tools; others are more difficult to install but can give you much longer service. This survey covers the range of weatherstripping products you’re likely to find at a local home center and provides you with the information you need to weigh cost, life expectancy, insulating efficiency, and installation effort.
Rigid Jamb This type of weatherstripping consists of a metal or vinyl flange attached to a tubular section of either hollow vinyl or rubber. Tu-
O
bular sections on higher-quality versions are
ver time, houses settle, doors sag, and
filled with silicone or foam, which provides
weatherstripping wears out, creating
better insulation and allows the weather-
small cracks around windows and doors.
stripping to hold its shape over time.
These leaks can account for 20% to 40% of
The flange is nailed, stapled, or
a home’s heat loss. As warm air escapes in
screwed to the jamb, and the tubular
winter (and cool air in summer), the good
section compresses to seal the open-
money you’ve paid for heating (or air-
ings. This product can be installed
conditioning) disappears, too.
on either doors or windows: Simply
Various contractors can bring in high-
close the window or door, butt the
tech detectors to determine where your
tubular section against it, and at-
house is losing heat, but doing a close in-
tach the flange to the jamb. Choose
spection on your own reveals more trouble
rigid-jamb styles that are adjustable;
spots than you might imagine. Adding or
they usually have elongated holes
replacing weatherstripping around windows
for fasteners. Don’t paint the tubular
and doors as well as sealing door bottoms
sections because that reduces their
are the obvious remedies to start with.
flexibility and efficiency.
Durability: Good Cost: 50¢/ft. to about $2/ft.
felt can snag on splinters or catch between sliding parts, it tends to wear out quickly on
Durability: nail-on V-strips: good adhesive V-strips: good Cost: $1/ft. to $2/ft.
Bronze
operable windows and doors. In areas prone to moisture, avoid using felt altogether.
Vinyl
Although it’s easy to install (and was the
V-Strips
standard 50 years ago), felt is relatively inef-
Sold in rolls, this flexible V-shaped weather-
products now on the market.
ficient compared to other weatherstripping
stripping compresses to seal gaps inside the tracks on windows and doors. V-strips come in bronze, vinyl, stainless steel, copper, and aluminum. One advantage of V-strips is that they disappear into the tracks of windows and doors. Adhesive-backed V-strips are the easiest to install. Metal V-strips hold up better than the vinyl versions but are trickier to install. The ends of mating pieces must be cut (using tin snips) for a tight fit, and driving brads every 3 in. amounts to a lot of hammering. (Use a nailset for the last taps on the brads.) To prevent the leaves from overlapping at the corners, trim the leaves at an angle. Metal V-strips are quite durable; as they age and compress, run a putty knife, nailset, or screwdriver down the inside of the crease to extend their life. One caveat: If doors and windows already fit tightly, adding springy V-strips in the tracks will make them harder to open Durability: Poor Cost: about 13¢/ft.
and close. On both windows and doors, you need to trim away parts of the weatherstripping to accommodate locks and pulley mechanisms.
Pressure-Sensitive, Adhesive-Backed Tapes These inexpensive tapes come in several varieties: nonporous, closed-cell foam; open-cell foam silicone; and various rubbers, including a product called EPDM (ethylene propylene diene monomer). It’s worth spending a few extra cents per foot to buy the more-efficient closed-cell foam or higher-quality silicones. Any of these styles can be purchased in various thicknesses and lengths. Although installation is easy—little more than peel-and-stick—be sure to clean surfaces using a mild detergent prior to setting the tape in place. In areas that see little use, such as inoperable windows, expect the tape to last roughly three years. On frequently opened windows, you’ll need to replace it in as little as a year. Securing the tape with tacks or staples helps to extend its longevity. As a general rule, apply this type of weatherstripping only on parts of windows that are not opened, such as around the
Felt
upper sash.
Felt weatherstripping can be purchased in rolls of various thicknesses, widths, and
Durability: Poor Cost: Vinyl foam: about 20¢/ft. X-treme Rubber: about 30¢/ft. Rubber foam: about 30¢/ft. ePDM rubber: about 80¢/ft. silicone: about $1.15/ft.
colors. It comes in either pressuresensitive or nail-on versions; some are adhered to a flexible vinyl or metal backing. The nail-on felt weatherseal
increased rigidity of the metal (or, to a lesser extent, vinyl) improves felt’s efficiency. Wool felt is the most durable. However, because
86
Insulation
Foam
silicone
Rubber ePDM
Window and Door Options OPTIONS FOR A DOUBLE-HUNG WINDOW Because window sashes slide in the jamb and past one another, not every type of weatherstripping is appropriate for all parts of a window. The window below is labeled with compatible weatherstripping and where it should be applied. SIDES OF UPPER SASH TOP OF Rigid jamb UPPER SASH (against sash) V-strips (inside track) Kerf-in (against sash) Tapes (inside track) SIDES OF Rigid jamb LOWER SASH (against sash) Rigid jamb (against sash) Kerf-in (against sash) Kerf-in (against sash) WHERE SASH MEETS SASH BOTTOM OF V-strips LOWER SASH (in the channel on Tapes (underside top sash’s lower rail) of sash) Rigid jamb, if the Rigid jamb top is inoperable (against sash) (underside of Kerf-in (against lower sash) sash) Felt (underside of sash) OPTIONS FOR AN EXTERIOR DOOR The swinging motion of a door allows you a greater choice of weatherstripping. In most cases, though, you must pay attention to how it should be applied. Some types of weatherstripping attach to the door jamb, and others to the doorstop. TOP OF LOCK SIDE DOOR OF DOOR V-strips V-strips (attach to (attach to jamb) jamb; notch to fit Felt around latch plate) (against doorstop) Felt (against doorTapes stop; place separate (attach to doorstop) lengths on each side Rigid jamb of latch plate) (attaches to jamb Tapes (abut and abuts doorstop) doorstop) Kerf-in (against Rigid jamb doorstop) (attaches to inside face of doorstop) HINGE SIDE Kerf-in (against OF DOOR doorstop) V-strips (attach to jamb) BOTTOM OF DOOR Felt Vinyl, metal, (applied to jamb) or wood thresholds Tapes Door seals, sweeps, (applied to jamb) or shoes; attachment varies by style Kerf-in (against doorstop)
sources Accurate Metal Weatherstrip Co. Inc. www.accurateweatherstrip.com Duck ® Products www.duckbrand.com Frost King ® www.frostking.com M-D ® Building Products www.mdteam.com Pemko Manufacturing ® www.pemko.com Randy Surley Manufacturing Company www.randysurleymfg.com Resource Conservation Technology Inc. www.conservationtechnology.com
Available at tool-rental outlets, this laminate trimmer has a 45-degree angled base that slides between the window jamb and stop to cut an angled groove for silicone-bead and other kerf-in weatherstripping.
Weatherstripping
87
Cut the groove toward the corners. Plunge the kerfing tool into the seam between the window jamb and the stop that holds the sash, and move it slowly toward the top and bottom corners of the jamb. a vacuum hose sucks up stray sawdust. silicone-bead and other kerfin weatherstripping is easy to install. Just cut the corners at a 45-degree angle, and press the flat fin into the kerf.
Kerf-In Plastic polymer-coated foam
A kerf is a blade-width notch cut into a door or window jamb with a saw or router. New doors often come with kerf-in weatherstripping in place. Although silicone might last up to 50 years, plastic and foam kerf-in weatherstripping might need replacement sooner. Simply pull out the old weatherstripping and snap the new, self-locking product into place. Although it’s possible to install kerfin weatherstripping on old windows not originally designed for it, you need to rent a corner-grooving tool (see the photos above left and on p. 87) to create the kerf. If you’re
silicone bead
tool savvy, these router-like machines are easy to use. Expect to pay about $70 per day for the rental.
Interlocking Metal Interlocking metal weatherstripping is an efficient way to seal air leaks around doors. It comes with two different pieces; one attaches to the door, and the other to the jamb and the threshold. When closed, the two pieces interlock to form a seal. This type Durability: silicone: excellent Plastic polymer and foam: good Cost: Plastic polymer: about 18¢/ft. Foam: about 38¢/ft. silicone: 35¢/ft. to $1.10/ft. 88
Insulation
of weatherstripping is the most difficult to install, a job best left to pros. If your doors already have interlocking metal weather-
stripping, keep it working smoothly by straightening any bends or dents that prevent the two pieces from fitting together.
Interlocking Metal Durability: excellent Cost: $1.50/ft. to $3/ft.
HINGE SIDE
Door Thresholds Because windows often slide in channels on
Jamb
Door
the jamb while doors simply close against the jamb, a typical door is more susceptible to air leaks than a typical window. The top and sides of a door can be weatherstripped
Groove cut into door
using many of the products seen on these pages. The bottom of a door, however, offers
Slight chamfer
a different challenge. To prevent air leaks properly, the thresh-
On the hinge side of the door, a bronze strip nailed to the jamb slips into a groove cut in the door.
old (on the floor) and the shoe or sweep (on the door) work together to create a seal. On exterior doors covered by overhangs or porches, you can install a shoe and a threshold. Doors exposed to the elements,
LATCH SIDE AND TOP Saw kerf
Door
aluminum with vinyl top and feet
adjustableheight oak and aluminum
Jamb
Interlocking bronze strips Saw kerf On the head and latch sides, bronze strips let into saw kerfs and nailed on both the door and the jamb interlock. DOOR BOTTOM Saddle Door
Vinyl top on paintable hardwood
Hook strip Rabbet
Threshold aluminum with vinyl top in bronze finish Durability: excellent Cost: $3.85/ft. to $7/ft.
At the door bottom, a bronze hook strip on the door engages the saddle screwed to the sill. Weatherstripping
89
however, should be outfitted with a thresh-
Other sweep styles actually wrap the
old designed to shed water away from the
bottom of the door and rely on a rubber or
house. If an existing wooden threshold
foam gasket along the door’s bottom edge
shows signs of water damage, simply replac-
to seal tight against the threshold. Again,
ing it will only postpone a larger problem.
look for a model with elongated screw holes that enable you to adjust the sweep. You
Door Sweeps
might have to remove the door to mount the sweep.
Installing a door sweep is the final step in
Automatic door sweeps are a fairly recent
sealing air leaks under a door. Sweeps come
invention, and they come in handy if the
in various styles, one of which simply at-
door opens over irregular stone or carpeted
taches to the outside of a door. Metal, vinyl,
floors, where a regular sweep would drag or
or wood versions connected to either felt or
bind. With automatic door sweeps, a vinyl
foam all can be cut to length with a hack-
flap drops down to seal leaks when the door
saw, backsaw, or tin snips, and most simply
is shut, but retracts when the door is open. If
screw to the bottom of a door. When trim-
it sounds like hoodoo, it’s not: A stop button
ming the sweep, cut it about 1⁄ 8 in. shy of
attached to the jamb lifts and closes the flap.
the overall door width. Some versions are nailed instead of screwed into place. If possible, opt for a version that screws into place
Matthew Teague is a furniture maker and journalist in Nashville, Tenn.
through elongated holes because they allow for easy adjustment.
aluminum with drip cap
white and brushed chrome with adjustable screw holes
Durability: Varies widely with use and by material. Cost: 33¢/ft. to $3.30/ft.
90
Insulation
A Buyer’s Guide to Windows By Sean Groom
W
hen you roll up to a house for the
radiation on a sunny day when you feel like
first time, you can’t help but notice
an ant trapped under a magnifying glass.
the windows. Their size, style, and place-
Second, a window must control solar-
ment determine if they’re appropriate to the
heat gain. I say control because heat gain
architectural style and, to some degree, if the
isn’t always bad. If you live in a heating
house will be a pleasure to be in.
climate—generally speaking, anywhere
For most people, that’s as much thought
north of Oklahoma with the exception of
as they give to windows. And that’s too
California—you should take advantage of
bad, because picking the right windows can
the free heat windows can provide.
lower heating and/or cooling costs, improve
Third, windows need to regulate airflow.
comfort inside the house, and improve
They should be airtight when closed and
indoor-air quality by dramatically limiting
also offer fresh air when you want it.
condensation. To buy the best-performing windows for
Finally, windows provide natural light and frame views both near and far.
your house, though, you need to know a bit
A Window Has Four Basic Jobs
Frame Materials Dictate Performance, Maintenance, and Cost
The first thing a window has to do is con-
Aluminum Aluminum frames are strong,
trol heat gain and loss. Technically, these
durable, inexpensive, and require little
temperature changes take place through
maintenance. Aluminum is highly con-
conduction, convection, and radiation. As a
ductive, however, leading to heat loss. To
practical matter, these temperature changes
achieve even modest insulating levels, the
affect your comfort. If you’re sitting next
frame and sashes must be carefully engi-
to a window, you’ll experience conduction
neered with thermal breaks. Even then, they
and convection when the glass acts as a cold
are best in mild desert climates or on impact-
radiator in the winter; and you’ll experience
resistant windows in hurricane zones.
about how they work and what they need to do.
windows
3
aluminum wood Clad Vinyl Fiberglass
Wood The only choice for some tradition-
ding should strengthen the window. Custom
alists, wood offers a pick of colors (and it
colors for aluminum cladding can match
can be changed later on). Wood frames are
any paint chip at an additional cost.
moderately priced and have good insulating value and structural strength, but they’re not low maintenance; they require periodic cleaning and painting, which adds to their overall cost.
92
Windows
Vinyl Vinyl frames are formed of extruded PVC. Multiple chambers in the frames and sashes add rigidity. These chambers also act as insulation in the same way as the airspace between glass panes; some manufacturers
Clad Windows with aluminum-, vinyl-, or
fill the chambers with foam insulation to
fiberglass-clad wood frames are the most
improve the frame’s insulating ability.
expensive. A clad unit offers the low-
Vinyl is available in only a few colors, gener-
maintenance durability of aluminum,
ally white and some variation on almond.
vinyl, or fiberglass on the outside and the
Darker colors absorb too much heat, causing
thermal resistance and appeal of wood on
vinyl to deform and degrade. It’s typically
the inside. Well-engineered aluminum clad-
the least expensive window.
Fiberglass The best you can get if you want
The best way to get a sense of window
to maximize a frame’s insulating ability,
quality is to read all the product literature
fiberglass is the least conductive material,
you can get your hands on and to look at
and the frame can be insulated with foam.
actual windows—a lot of them. Go to the
More expensive than aluminum, vinyl, or
big-box store and the local building supply,
wood, fiberglass requires little maintenance
and open and close the windows on display,
and is durable and extremely strong. It can
paying attention to how the corners are
be extruded in low-profile frames and sashes
joined, how well the sashes seal, and how
in several colors and is paintable. Another
rigid the unit is.
advantage is that as the temperature changes,
On vinyl windows, look for continuous
fiberglass expands and contracts at a rate
thermally welded corners. Examine the cor-
almost identical to the glass. This helps to
ner cutaway displays of aluminum windows
prevent seals along the glass from failing.
for a continuous thermal break in both
Composite Composite windows, like composite decking, are made of wood fibers (sawdust) mixed with vinyl resins. Up to 40 percent of the window content is recycled. Most, if not all, composite windows are sold as replacements by the Renewal By Andersen® division of Andersen® Windows. The material’s tradename is Fibrex®. It looks a lot like wood, will not rot, requires little maintenance, and can be stained on the inside.
What Makes a Good Frame? When most people choose windows, they begin by considering the frame material. They might be predisposed to traditional wood or low-maintenance vinyl. However, according to Nils Petermann at the Efficient Windows Collaborative, the most important factor to consider is the frame’s durability. This is where I’d like to refer you to an independent organization that provides unbiased durability ratings for window frames. Unfortunately, there isn’t one. You can make educated guesses about durability based on the frame material. But whether it’s wood, vinyl, fiberglass, aluminum, clad, or composite, a well-constructed window lasts longer and performs better than a poorly constructed one regardless of the relative benefits of its frame material.
frame and sash. On a clad window, the cladding should have well-sealed corners and gaskets to prevent water from getting behind the cladding. Aluminum is an excellent heat conductor, so be sure that aluminum cladding doesn’t contact conditioned interior air at any point. Another way to sift through the options is to talk to reputable builders and architects in your area. Ask what windows they use and how long they have been using them. They won’t stick with windows that make their clients unhappy. Thirty years ago, when single-pane windows were the rule rather than the exception, companies looking to improve window performance focused their research on insulating glass. It was the lowest-hanging fruit. They’ve done such a good job that the R-value of insulated glass is good enough to make the window frame the weak link in the thermal chain. That’s one reason why manufacturers list performance data for relatively large windows, say, 4 ft. by 5 ft. (When you’re comparing windows, make sure the performance data are for windows of the same size.) Windows with large areas of glass yield better performance numbers because the frame is a smaller percentage of the window area. Savvy window designers understand this and tweak their windows accordingly for optimal performance. By using strong materials that permit low-profile sills, sashes, and jambs, they minimize the size of
A Buyer’s Guide to Windows
93
Window anatomy
T
o understand and appreciate how a window works, you need to know the components that make up a basic window. While there are several types of windows besides the double-hung and casement illustrated here, the terminology used to describe each piece is universal.
windows need to insulate Sealed airspaces improve insulation. The more insulating spaces in the glass unit, the better the performance; tripleglazed windows are among the most energy efficient you can buy. Aluminum, vinyl, and fiberglass frames use extruded chambers both for strength and as a thermal break. Filling these cavities with foam provides additional insulation. Solid-wood frames are about as efficient as vinyl. Stop Frame Jamb
doUbLe-GLaZed insULated FiberGLass
Muntin
Warm-edge spacers
Sash
sinGLe-GLaZed soLid Wood
Insulated glazing Weatherstripping
Sill
94
Windows
triPLe-GLaZed aLUMinUM-CLad Wood
Window dna: the nFrC Label by the numbers U-FaCtor A measure of the insulating value. U-factor is the nonsolar heat flow through all parts of the window (glass, frame, and sash). A lower number means better insulation and greater performance. visibLe transMittanCe (vt) A measure of the amount of visible light that passes through the window. Values range from 0 to 1 (a higher number equals more light). However, most ratings are between 0.3 and 0.8 because they take into account the light blocked by the frame. Choose windows with higher VT to maximize daylight and views.
soLar heat Gain CoeFFiCient (shGC) The percentage of the sun’s solar heat that passes through the window. Higher numbers mean more passive solarheating potential.
air LeaKaGe (aL) A measure of the amount of air passing through the window assembly; a source of heat gain and loss. This optional rating is expressed in cubic feet per minute through a square foot of window. Look for ratings under 0.3; lower is better.
Condensation resistanCe A relative scale from 0 to 100 based on the window’s properties. It predicts the likelihood of condensation, with higher numbers indicating less condensation.
the conductive frame while being sure to incorporate materials that reduce air leakage. Frame material can also influence how
Insulated Glass Reduces Heat Loss
long a window stays airtight. Like most
Manufacturers typically refer to glass as
building materials, windows expand and
glazing. Using glazing as a noun is a bit
contract with changes in temperature and
pretentious, like referring to a window as a
humidity. When you see a window with
fenestration, but it does give the sense that
moisture between panes, it’s likely that
glass assemblies in today’s windows are a far
movement between the glass and the sash
cry from the single-pane windows installed
broke the insulating seal. By choosing stable
in the 1970s.
materials, you can reduce stress on the seal
Those single-pane windows have been
and increase the window’s longevity. Fiber-
abandoned in most heating climates be-
glass expands at the rate of glass, while
cause glass is a horrible insulator. A standard
aluminum and vinyl expand respectively
window today relies on an insulated glass
3 times and 7 times more than glass. Wood
unit (sometimes called an IG). This unit is
moves in response to humidity changes
a sealed sandwich of two or three pieces of
rather than temperature.
glass with an airspace between the panes. IG units are manufactured by a few glass companies that supply the hundreds of window manufacturers in North America.
A Buyer’s Guide to Windows
95
Spacers Are Potential Weak Points
What’s a U-Factor?
U
-factor rates a window’s insulating properties by measuring the flow of nonsolar heat through the window. You can think of it as the rate of conduction; the lower the U-factor, the less heat will flow through the window. (U-factor is the reciprocal of the more familiar R-value used to rate insulation. R-value measures resistance, so higher numbers are desirable.) Although we tend to think of a window as primarily glass, the frame makes up 20% to 30% of the unit. U-factors are measured for the edge of the glass area, the center of the glass area, and the frame; but the important U-factor is for the entire window unit. Buy-
Spacers between glass panes perform three functions: They maintain a uniform separation between pieces of glass, they provide a good adhesive surface for the glass, and they create an airtight seal for the insulating cavity. Although you should choose windows based on their overall performance ratings, the spacer, while small, substantially impacts ing decisions should be based on this number, which appears on the NFRC label (above). U-factors for operable windows range from 0.14 for a superinsulating suspended-film unit to 0.5 or so for a basic double-pane window from a big-box store. Lower U-factors correlate with higher prices.
a window’s U-factor and condensation resistance. The spacer’s job is complicated by the fact that it’s in contact with both the inside and outside surfaces of the window, forming a bridge between indoor and outdoor environments. Because the spacer is more conductive than the air or gas fill, it changes the temperature of a 21⁄ 2-in.-wide band around the edge of the glass. As a consequence, the window’s overall U-factor is affected. In smaller windows, the 21⁄ 2-in. temperature band is a larger percentage of the window
The airspace between glass panes, usually 1⁄ 2
in. to 2⁄ 3 in. thick, serves as insulation by
the Achilles’ heel of all windows, a casement
duction. A single clear pane has a U-factor
window performs slightly better than a
of 1.04, but a sealed double-pane unit has
double-hung of the same size because the
a U-factor of 0.5 (see “What’s a U-Factor?”
former has less spacer area. Likewise, the
above). Adding a third pane improves the
thermal performance of true divided-lite
U-factor to 0.3.
windows made up of multiple IG units suf-
Replacing the air with gas improves the
fers because of all the spacer area in the win-
insulating value of the window. Manufactur-
dow. (Simulated divided lites can also affect
ers use argon or krypton gases because they’re
U-factor if the grille creates a thermal bridge
inert—chemically stable and nonreactive—
between the panes.) Spacers are made of aluminum, steel,
less conductive than air. Argon and krypton
fiberglass, foam, and thermoplastics, often
also reduce convective losses because the
in some combination. Foam spacers have
gases are heavier than air, reducing gas
the lowest U-factor, while aluminum has the
movement within the insulating space.
highest. Today, quality windows use “warm-
Krypton performs slightly better than ar-
Windows
U-factor. While spacers can be considered
reducing the transfer of heat through con-
and because they reduce heat loss, as they are
96
and has a greater effect on the window’s
edge” spacers. (It’s worth noting that warm-
gon, but its bigger advantage is that the op-
edge means only that it’s less conductive
timal spacing between krypton-filled panes
than aluminum.) A good warm-edge spacer
is narrower than what’s required for argon.
raises the interior surface temperature of the
That means less stress on the sashes, particu-
glass along the perimeter of the window.
larly in triple-pane windows.
This is especially important at the window’s
bottom edge, which is most subject to condensation. At 0°F outside, a good spacer in-
the role of Low-e
creases the temperature at the bottom of the inside glass pane by 6°F to 8°F. As a result, a more comfortable relative-humidity level indoors is possible during the winter without window condensation.
Coatings Improve Performance
1. Reflects short-wave radiation to reduce heat gain. 2. Filters UV-rays that cause fading.
1 2
3. Tinted coatings, not low-e, temper visible light.
3
4. Reflects long-wave radiation to reduce heat loss.
4
Energy-efficient windows were developed during the previous energy crisis. When Jimmy Carter was installing solar panels on the White House and making conservation a priority, the Department of Energy’s Lawrence Berkeley National Laboratory was charged with finding ways to conserve energy. Windows were among their targets. The insulating windows of that era allowed an inordinate amount of heat to escape. The lab’s scientists concluded that by using existing technologies to deposit a virtually invisible metal or metal-oxide coating on the glass, insulating windows could be dramatically more efficient. This coating is transparent to visible light, but blocks long- and short-wave radiation by reflecting it. Known as a low-e (for low-emissivity) coating, it’s common today even on low-cost windows. Depending on the nature of this thin coating and which window surface it is applied to, the coating can reflect heat back into the room to conserve it or filter sunlight to keep heat out. Using a coating on two different glass panes can fine-tune the amount of heat that’s retained in each direction. The measure of the amount of the sun’s heat a window lets through is the solar heat gain coefficient. SHGC in shorthand, it ranges from 0 to 1, where 1 is uninterrupted heat gain. A clear-glass, two-pane insulated window has an SHGC between 0.56 and 0.68, depending on the frame material and construction. The size of the air gap, which is influenced by frame design, and the amount of light blocked by the frame and
A double-pane IG with two low-e coatings can achieve an SHGC of 0.33 (glass-only value). As the SHGC is minimized, the Ufactor declines, which has implications for selecting windows in climates with heating and cooling seasons.
Choosing Energy-Saving Windows reGionaL: a Good aPProaCh If you’re interested in efficient windows, the starting point is an Energy Star rating. The greatest chunk of energy savings comes from good insulating properties. Energy Star performance prescriptions dictate that the colder the climate, the lower the U-factor you’ll want. In southern climates, where airconditioning dominates energy consumption, Energy Star ratings shift focus to a lower SHGC to reduce the impact of the sun. The Department of Energy divides the United States into four climate regions (see the map on p. 98). Under the Energy Star program, each region is assigned threshold U-factor and SHGC ratings for a qualifying window (see the chart on p. 98). A doublehung vinyl window that’s Energy Star qualified in all four zones might start at around $14 per sq. ft., with a clad frame starting at around $28 per sq. ft.
grille affect the SHGC. A Buyer’s Guide to Windows
97
enerGy star reQUireMents region
U-factor
shGC
North
< 0.35
Any
North/Central
< 0.4
< 0.55
South/Central
< 0.4
< 0.4
South
< 0.65
< 0.4
< less than or equal to
dULUth, Minn. insulated fiberglass frame, double pane with three films U-factor = 0.09 (R-11) SHGC = 0.26 Price = $280/sq. ft.
san FranCisCo, CaLiF. insulated vinyl frame, double pane with one film U-factor = 0.27 (R-3.8) SHGC = 0.47 Price = $50/sq. ft.
LoCaL: a better aPProaCh
Best Approach” on p. 100) and are based on
In the United States, the performance
a benchmark house.
characteristics on an NFRC label (see the sidebar on p. 95) provide a moment-in-time
U-factor, high-SHGC windows in the north
snapshot of performance, but don’t relate
region, the north/central zone, and the
anything about the long-term energy conse-
upper half of the south/central area; and low
quences and peak load demands of window
U-factor, low-SHGC windows in the south-
choices.
ern reaches of the south/central area and in
To get a better-performing window than the Energy Star minimum, you need to take
98
Windows
Their modeling recommends low
the south region. The most energy-efficient windows in all
energy costs into account. A quick-and-dirty
locations, except San Francisco and Flagstaff,
tool from the Efficient Windows Collabora-
Ariz., are at least triple-glazed with insulated
tive (www.efficientwindows.org/selection
vinyl or fiberglass frames. These windows
.cfm) compares the energy costs for a range
are hard to find and expensive. The nice
of windows with different performance char-
thing about the collaborative’s website is
acteristics. The cost figures are generated us-
that it shows how much annual energy
ing RESFEN software (see “Site Specific: The
expenditures rise if you opt for a readily
LoUisviLLe, Ky. insulated fiberglass frame, triple pane U-factor = 0.23 (R-4.3) SHGC = 0.39 Price = $80/sq. ft.
neW orLeans, La. Clad-wood frame, double pane U-factor = 0.3 (R-3.3) SHGC = 0.21 Price = $52/sq. ft.
available double-glazed window with two
in peak demand periods with higher rates,
low-e coatings and an uninsulated vinyl
and by reducing peak loads saves on
or clad-wood frame. Exceeding Energy Star
mechanical costs with a smaller air-
minimums saves money over the life of the
conditioning system.
window. (Examples shown are options ex-
Window glass isn’t the only or even the
ceeding Energy Star thresholds. Consult the
best way to block summer sun. Deciduous
collaborative’s website or RESFEN for energy
trees on the south, east, and west sides of
performance for your location. Prices are ap-
a house work very well. Another strategy is
proximate window cost.)
the use of overhangs and shading devices.
Critics of Energy Star argue that in heat-
If you need to rely on window glass to
ing climates, the emphasis on insulating-
control solar gain in the South, you’ll need
value performance to the exclusion of solar
low-SHGC, or spectrally selective, windows.
heat gain misses an opportunity. By omit-
They reflect short- and long-wave infrared
ting an SHGC requirement in the north
radiation to filter out 40% to 70% of incom-
region, window companies can market a
ing heat. Sometimes known as low-e2 or
single low U-factor, low-SHGC glass pack-
low-e3, the second- and third-generation
age that meets Energy Star requirements
low-emissivity coatings on these windows
in all regions. An Energy Star label on low
not only reduce solar gain, but also filter
U-factor, low-SHGC windows in cold north-
more than 99% of the UV-light that causes
ern regions of the United States means
color fading.
homeowners who think they are buying
Generally, you want a window to block
energy-efficient windows are actually pay-
solar gain but let in visible light. The win-
ing more in heating costs and adding more
dow’s light-to-solar-gain ratio (VT/SHGC)
carbon emissions to the atmosphere than if
provides a gauge of its relative efficiency
they had purchased windows that accounted
in transmitting light while blocking heat
for passive solar-heating opportunities. (For
gain. The higher the number, the more
some sites, a very low U-factor, such as the
light transmitted without adding excessive
Duluth, Minn., example, is the best option.)
amounts of heat. In a cooling-dominated cli-
The Department of Energy is reportedly re-
mate, a ratio above 1.0 is better because light
evaluating the standard.
transmittance is higher than heat gain.
While insulating properties may not seem
If glare is a problem, windows tinted
as important in the South, where Energy
bronze, green, or blue limit visible light and
Star thresholds are fairly high, a low U-factor
are spectrally selective with a low SHGC.
helps to keep indoor temperatures cool. This
However, because they absorb infrared radia-
reduces peak cooling loads and saves money
tion rather than reflect it, tinted windows
in two ways: It reduces energy consumption
radiate heat.
A Buyer’s Guide to Windows
99
ing (E.R.) that makes it easy to evaluate the
Films Create Super Windows
trade-offs in heating-dominated climates.
Another way to control the flow of heat
By weighing the amount of solar-heat gain
through a window is with suspended films.
against interior-heat loss through the win-
These films come in two varieties: high solar
dow and heat loss through air leakage, the
gain and low solar gain.
Canadians have it easy Windows sold in Canada have an energy rat-
E.R. indicates whether a window is a net
so lightweight and thin, as many as three
ergy neutral (E.R. equals 0), or a net loss of
films can be suspended between two glass
energy (negative E.R. value). If you live in a
panes. The additional insulating spaces in-
north or north/central zone in the United
crease the insulating ability of the window,
States or Canada and you’re buying a win-
replicating the performance of three-, four-,
dow from a Canadian manufacturer, simply
or five-pane windows without the weight.
choose the highest E.R. possible.
Serious Windows® uses this approach to cre-
SITE SPECIFIC: The best approach Engineers and efficient-house designers use complex modeling software to evaluate the effect of window options on energy consumption. Rather than buying the same window for an entire house (as you would using Energy Star guidelines or the Efficient Windows Cooperative website), they tune the windows to optimize glass performance for each orientation. The average homeowner or contractor
high and low solar-gain properties. The company’s premium fixed window has an insulating value of R-11.1 (U-factor 0.09), nearly rivaling many wall insulations. The operable version of the window is R-7.1 (U-factor 0.14). Considering that the average insulating window is the equivalent of R-1 to R-3, Serious Windows live up to their name.
Let the Light Shine In Solar gain and insulating values aren’t the
house and compare the effects of different
only ways that windows save energy and
windows with RESFEN, a free software pack-
keep you comfortable. Windows also control
age from the Department of Energy’s Law-
the view and the amount of natural light. Daylighting, or window-placement strate-
windows.lbl.gov/software/resfen/resfen
gies to maximize natural light, save money
.html). Unfortunately, to get the most out of
by reducing the need for electric lighting. Al-
the program, you’ll have to slog through the
though placement is a design issue, window
manual.
styles and glass properties affect the amount
Generally, in heating climates, south-
of light infiltration. The visible transmit-
facing windows have a high SHGC (greater
tance (VT) rating on the National Fenestra-
than 0.5), and east- and west-facing win-
tion Rating Council’s label (p. 95) allows you
dows have a low SHGC (less than 0.3) to
to compare the amount of light that passes
prevent solar gain in the summer.
through windows, taking into account the
Until recently, common wisdom was that the SHGC on north-facing windows should match east- and west-facing windows, but software modeling has shown that highSHGC north-facing windows don’t lose any energy.
Windows
ate high-performance windows with both
can model the energy performance of a
rence Berkeley National Laboratory (http://
100
Because these films (similar to mylar) are
source of energy (positive E.R. value), en-
light blocked by frames and grilles.
Impact-Resistant Glass Offers Protection Although they don’t affect a window’s energy performance, a few options can make you safer. Tempered glass, for example, can be specified for windows located where someone could potentially fall into one. Many of these locations are covered by code and include windows within 18 in. of the floor, next to doors, in showers or bath areas, and along decks, patios, and walkways. If you live in a coastal area—particularly along the Atlantic and Gulf coasts, where building codes demand protection during hurricanes—or in a tornado-prone area, you can specify impact-resistant glass. Using the same technology as car windshields, a plastic sheet is laminated between two pieces of glass so that the window maintains its integrity after the glass is broken. Window frames can also be reinforced to withstand impact. Available in three different strengths (impact zones 2, 3, and 4), the toughest windows in impact zone 4 must withstand strikes from at least two 8-ft.-long 2×4s traveling at 50 ft. per second, followed
27. Every increase of 10 in the STC cuts the amount of sound transmitted by half. Companies such as Milgard®, Atrium®, Marvin, and Serious Windows have windows in the 40 to 47 STC range.
Self-Cleaning Windows Reduce Maintenance Demands For those of you who say, “I don’t do windows,” technology has finally caught up with your sentiment. Several big glass companies market coated glass that resists the buildup of dirt. Product names include Neat® Glass by Cardinal, Activ™ by Pilkington®, and PPG’s SunClean®. By making the glass smoother and hydrophilic, rainwater collects in sheets on the surface and slides off the glass quickly, cleaning the window. Some windows include a titanium-dioxide layer that reacts with UVlight to help organic materials decompose, so dirt washes away more easily.
Window Styles doUbLe-hUnG
by 9,000 cycles of negative and positive
Traditional window composed
pressure simulating hurricane-force winds.
of two sashes that slide verti-
Windows That Keep the World at Bay
cally. A single-hung window looks identical, but the top sash is fixed. Pros: Available with a wide va-
Manufacturers also offer variations of
riety of grille patterns to match
pebbled, frosted, and wavy glass that add
different architectural styles.
privacy to bathrooms, bedrooms, and other
Sashes usually tilt in for easy
sensitive spaces.
cleaning of the exterior.
If you live near a busy road, near train tracks, or under a flight path, acoustic windows can take the edge off loud or constant noise. Even if they don’t readily advertise the fact, many window companies sell sound-attenuating windows. Residential “quiet” windows are likely to be rated with a sound transmission coefficient (STC). A typical double-pane window has an STC of 25 to
Cons: Sashes rely on draftier sliding-style weatherstripping. The bottom edge of the upper sash is exposed to outdoor temperatures on two faces, increasing surface area for thermal bridging. Two sashes increase spacer area, increasing U-factor. Less than half the window area can be open for ventilation. A Buyer’s Guide to Windows
101
awning
Horizontal slider
Tilt-and-turn
Fixed
Casement
Hopper
aWninG Top-hinged window that usually opens
prove U-factor. Largest ventilation area of
outward with a crank.
any window style. Opening can be oriented
Pros: Good-sealing compression-style
to “scoop” prevailing breeze.
weatherstripping. Single glass unit and re-
Cons: Screen on inside of window. Hinge
cessed sash improve U-factor. Provides ven-
design might not allow outside of window
tilation while it’s raining. Often used above
to be cleaned from inside. Open window can
and/or below large fixed windows for venti-
present a hazard if installed along a walk-
lation and additional daylight.
way, deck, patio, or porch.
Cons: Screen on inside of window. Open window can present a hazard if installed along a walkway, deck, patio, or porch.
horiZontaL sLider The two sashes slide past one another on tracks like a sliding patio door.
tiLt- and-tUrn
Pros: Can be easier to open than other slid-
Dual-action window that can swing in like
ing styles, especially when placed over a
a door or tilt from the bottom like a hopper
counter.
window for ventilation.
Cons: Sliding weatherstripping and greater
Pros: Ventilation options. Secure multipoint
sash area lower U-factor and airtightness
locking. Compression weatherstripping.
ratings.
Large egress area and easy cleaning. Cons: Shades and drapes can interfere with operation.
CaseMent Side-hinged window that usually opens
Windows
An inoperative window available in shapes that match operable windows, or as accent windows such as half-rounds to create Palladian windows and octagons.
outward with a crank. In-swing versions are
Pros: Improved airtightness. Can be made
available.
in nonstandard, custom shapes.
Pros: Compression-style weatherstripping.
Cons: Doesn’t satisfy egress requirements.
Single large glass unit and recessed sash im102
FiXed
hoPPer
insert-style replacement fits inside an existing new-construction window.
Tilt-in bottom-hinged window. Pros: Compression-style weatherstripping. Single glass unit and recessed sash improve U-factor. Cons: Hazardous if installed at head height or lower.
Choosing Replacement Windows
Sources There are hundreds of window manufacturers, the majority of them local companies. a sample of large national and smaller specialty manufacturers is listed here. Visit www.efficientwin dows.org for a more comprehensive list.
You have three choices for replacing existing windows: a sash-only replacement; an insert-style frame and sash replacement window; or a new-construction window. If the existing frames have water damage, the only choice is a new-construction window (see the photos on p. 92). If you’re looking to improve comfort or
new-construction window. Installation costs
Accurate Dorwin www.accuratedorwin.com
are lower, however, because it leaves the ex-
Andersen
energy performance, replacing the sashes or
isting trim in place and doesn’t require any
www.andersenwindows
using a frame insert can help. They’re a good
siding removal.
choice on older homes where you want to
Regardless of the type you choose, re-
.com
Integrity ® www.integritywindows.com
preserve period trim, but from an energy
placement windows are expensive. If you’re
and comfort standpoint, they’re not the
trying to save on energy expenses, new win-
best option.
dows shouldn’t be considered until you have
Loewen ®
improved the insulation and the air-tightness
www.loewen.com
of the rest of the building envelope.
Marvin
Former Fine Homebuilding editor Sean Groom is a freelance writer in Bloomfield, Conn.
Milgard
Replacement windows that leave the existing frame in place don’t stop air leak-
stuffed between the window and the rough
www.jeld-wen.com
www.marvin.com
age. If you’ve ever pulled out an old window, then you’ve seen fiberglass insulation
Jeld-Wen ®
www.milgard.com
Pella
opening. Typically, the insulation is dirty. It
www.pella.com
wasn’t dirty when it was put there; dirt was
Quantum
filtered out of the air moving through and
www.quantumwindows
around the window frame.
.com
Serious Windows
Another negative is that insert-style frame
www.seriouswindows.com
and sash replacement windows reduce the
Thermotech
glass area because the unit fits inside the
www.thermotechfiberglass
existing frame. You might be willing to live
.com
with diminished views, but are you will-
Weather Shield ®
ing to pay for that privilege every year? In
www.weathershield.com
a southern climate, the reduced glass area does not affect heating bills, but in northern heating climates, reducing the south-facing glass area gives away a lot of free heat. An insert-style frame and sash replacement window is generally a bit pricier than a
Sash-only replacement A Buyer’s Guide to Windows
103
windows
3
Do Europeans Really Make the Best Windows? By Martin Holladay
A
good window seals out cold, windy weather and admits as much light as
Only a handful of window manufacturers in the United States and Canada sell
possible into a house’s interior. While those
high-performance windows suitable for
functions seem rather obvious, some claim
cold-climate homes. Sensing an opportunity,
a new class of window can perform these
manufacturers from Germany and Austria
duties better than any window made in the
have eagerly filled the market niche by in-
United States.
troducing a host of high-performance units to American builders.
Defining High Performance The two most important measures of a window’s performance are its U-factor and its solar heat-gain coefficient (SHGC), numbers that can be found on a new window’s National Fenestration Rating Council (NFRC) label. A window’s U-factor is the inverse of its R-value; the lower the U-factor, the better the window is at resisting heat flow. A low U-factor is desirable in all climates. While the best double-glazed windows have a U-factor of about 0.27, triple-glazed windows have U-factors as low as 0.17.
Efficient Wood Windows from Across the Pond
Closed
tilt
climate houses need windows with a low SHGC (0.30 or lower), especially on the west elevation. Cold-climate builders should look for windows with a low U-factor and a high
Optiwin® windows, which exemplify Pas-
SHGC. The higher a window’s visible-light
sive House® certified European windows, are
transmittance (VT), the better. VT indicates
manufactured by Müller Schreinerei in Laut-
the amount of visible light that enters a
enbach, Germany. The company produces
window.
two cold-climate windows, the Three-Wood
Many high-performance European win-
(Drei-Holz) window and the Two-Wood
dows meet stringent standards established
(Zwei-Holz), pictured on the facing page.
by the Passivhaus Institut in Darmstadt,
Like all European tilt-turn windows,
Germany. To be certified, a Passive House
Optiwin windows open inward. This fea-
window needs a European U-factor no
ture allows the windows to be installed in
greater than 0.80 W/m²•K° (see “It’s Difficult
a recessed location so that foam sheathing
to Compare U-Factors,” on p. 106).
(a common feature on superinsulated walls)
In central Europe, such low-U-factor win-
can be extended to cover the exterior of the
dows maintain an interior pane temperature
window frames. This installation detail—
of 17°C (62.6°F) or more on the coldest day
sometimes referred to as “overinsulating the
of the year. The Passive House U-factor
exterior of the window frames”—improves
requirement can be achieved only by win-
the windows’ overall thermal performance.
dows with insulated frames and triple glaz-
SHGC is a measure of how much solar
ing with two low-e coatings and warm-edge
heat is admitted through a window. In general, windows with a high SHGC help to
turn
spacers. U.S. distributors now sell Passive House
heat a house (a desirable feature during the
windows from several European manufactur-
winter), while windows with a low SHGC
ers, including Internorm® and Silber in
help to prevent a house from overheating
Austria, and Henzmann, Optiwin, Pazen
(a desirable feature during the summer).
ENERsign, and Unilux UltraTherm in
Cold-climate houses need windows with a
Germany.
high SHGC (at least 0.39), especially on the south elevation. On the other hand, hotDo Europeans Really Make the Best Windows?
105
It’s Difficult to Compare U-Factors The U-factors reported by European window manufacturers—whether given in European units (W/m²•K°) or North American units (Btu/ft²•F°)—are difficult to compare with U-factors reported by North American manufacturers. European and North American laboratories use different protocols to test A core of cork increases thermal performance.
window U-factors, and most glazing experts agree that European U-factors would look worse if the windows were tested according
The interior of the frame, which is made of either fir or spruce, is left exposed.
Triple glazing with warm-edge spacers is filled with argon or krypton. OPTIWIN U-factor: 0.137 SHGC: 0.53 VT: 0.72 (glass only) Kerfed-in bulb weatherstripping
Aluminum cladding increases durability
Locking hardware that’s been compared to that of a bank vault helps to compress extensive weatherstripping to limit air infiltration.
Cork acts as a thermal break.
106
Windows
to NFRC requirements.
U.S. distributors of European windows don’t follow a consistent method for reporting U-factors. Some use European metric units, while others report North American
MARVIN ULTIMATE PUSH-OUT CASEMENT U-factor: 0.28 SHGC: 0.25 VT: 0.42 Cost: $670
U-factors or even R-values. Although the NFRC requires U-factors and SHGC to be based on the performance of the whole window, including the frame, many European manufacturers report U-factor and SHGC numbers that measure the performance of the glazing alone. There is a straightforward conversion factor for converting a European U-factor in W/m²•K° to a North American U-factor in Btu/ft²•F°: Simply divide by 5.678. Unfortunately, while this method converts the units, it doesn’t account for the fact that the European protocol tests windows of a different size from the size used in North American testing, or for the fact that European windows are tested at different temperatures than required for North American tests.
An American Standard To appreciate the performance of the windows featured here, it’s helpful to look closely at a typical window made by an American manufacturer. The argon-filled, doublepaned window made by Marvin (above) is an example of a unit suitable for houses built to code minimums.
The European Difference For the most part, the glass in European Pas-
Passive House Institute US, gives a bottomline analysis: “Our experience has been that the overall performance of the fiberglassframed Canadian and U.S. windows is almost as good as the German Passive House windows if you look at the overall systems design [using Passive House Planning Package software].” However, European window manufacturers continue to push the performance envelope, and glazing manufacturers are always striving to improve their products. The latest versions of low-U triple glazing from Europe may have a higher SHGC than comparable low-U triple glazing available in North America. According to some window experts, European manufacturers are already selling windows with better insulated frames and glazing with a slightly lower U-factor than any frames or glazing available from North American manufacturers. Typical European Passive House windows
sive House windows is quite similar to the
have composite frames, often including a
glass used in the best Canadian windows:
wood lamination on the interior, a core of
argon- or krypton-filled triple glazing with
foam or cork to act as a thermal break, and a
two low-e coatings and warm-edge spacers.
weather-resistant exterior cladding of alumi-
That’s why many energy experts report that
num or rot-resistant wood.
the thermal performance of the best Euro-
Although the wide frames on European
pean windows is about the same as that of
windows reduce the windows’ thermal
fiberglass-framed, triple-glazed Canadian
performance—especially their potential for
windows. Katrin Klingenberg, founder of the
solar heat gain—compared to narrow-framed Do Europeans Really Make the Best Windows?
107
North American fiberglass windows, the thermal breaks incorporated in European THERMOTECH FIBERGLASS U-factor: 0.19 SHGC: 0.42 VT: 0.44
Fiberglass frames don’t expand and contract like vinyl, which leads to longerlasting windows.
frames are usually more effective than those used by North American manufacturers.
North American Products Rely on Narrow Frames and Synthetic Materials Although European triple-glazed windows are well built and attractive, they cost far more than North American windows with similar performance specs. (For an operable triple-glazed casement window measuring 8 sq. ft., you can expect to pay between $400 and $520 for an Inline, Fibertec, or Thermotech® window. A Serious window with Heat Mirror™ glazing will have a lower VT rating, but it will cost about the same—$400 to $560, depending on the glazing chosen.) Windows from Europe also have a long lead time—anywhere from 10 to 12 weeks. Unlike almost all U.S. manufacturers, Canadian manufacturers of fiberglass windows offer full-thickness (13⁄ 8 in.) triple-glazing. Even when U.S. manufacturers offer triple glazing, it’s usually thin (1 in. or 7⁄ 8 in.), low-performance glazing. While Canadian window manufacturers offer both low-solar-
SERIOUS WINDOWS U-factor: 0.13 SHGC: 0.20 VT: 0.30
gain and high-solar-gain triple glazing, it’s difficult to buy high-solar-gain triple glazing from a U.S. manufacturer. Canadian fiberglass windows have other attributes that make them more attractive than European offerings. Canadian windows
Heat Mirror glazing is high performance, but comes with skepticism.
have narrower frames than European windows. Because frames have a lower R-value than a superinsulated wall, narrower frames mean better thermal performance overall. Also, narrow-framed windows allow more light and more solar heat gain than wideframed windows. When looking for high-performance windows made domestically, you’ll come across the following materials.
108
Windows
PULTRUDED FIBERGL ASS FRAMES
PARADIGM WINDOWS U-factor: 0.22 SHGC: 0.23 VT: 0.38
The pultruded fiberglass used for the best Canadian window frames is similar to the fiberglass used to make stepladders, only denser and smoother. Even when left unpainted, pultruded fiberglass is extremely
Triple-glazed windows are a must on highperformance homes, and vinyl frames help to reduce cost.
durable and weather resistant. Because it has a coefficient of thermal expansion that closely matches that of glass, it’s a much more suitable material for window frames than vinyl.
HEAT MIRROR GL AZING Heat Mirror glazing has only two panes of glass; the performance of the glazing is improved by one or more stretched plastic films suspended between the two panes. The
sources
plastic films create two or three separate air spaces between the inner and outer panes of
nortH aMEriCan
glass, mimicking the performance of triple
Accurate Dorwin:
or quadruple glazing but with less weight.
www.accuratedorwin.com
The best-known manufacturer of Heat Mirror windows is Serious Materials. Serious offers windows with lower U-factors than any triple-glazed window. Its best-performing operable window (a 1125 series casement or awning window with three plastic films)
windows also have a low SHGC (0.23). Like
Duxton: www.duxtonwindows.com
almost all U.S. window manufacturers, Para-
Fibertec:
digm Windows doesn’t yet offer high-solar-
www.fibertec.com
gain triple-glazed products.
Inline: www.inlinefiberglass.com
Paradigm:
a very low visible transmittance (0.30). In
High-Performance Windows Don’t Make Sense in All Homes
other words, the windows don’t let in much
The high cost of triple-glazed windows is
www.thermotechfiberglass
hard to justify unless you’re building a su-
.com
perinsulated house in a cold climate. But
EUroPEan
once your wall specs reach the R-40 level,
Bieber:
triple-glazed windows start to make sense.
www.bieberusa.com
A triple-glazed Optiwin tilt-turn window
Heinzmann:
has a whole-window U-factor of 0.13. The low-U-factor glazing comes with a downside, however: a very low SHGC (0.20) and
light or heat. European window manufacturers (and most Passive House builders in the United States) have been reluctant to use Heat Mirror windows due to lingering skepticism about the long-term durability of the plastic films and an unwillingness to accept lower SHGC and VT ratings.
VINYL FRAMES WITH TRIPLE GL AZING Builders experiencing triple-glazing sticker shock may want to consider a lower-cost option: vinyl windows. Paradigm Windows of Portland, Maine, offers casement windows with foam-injected frames. Paradigm’s best performing krypton-filled triple-glazed casement windows have a whole-window U-factor as low as 0.17. Unfortunately, these
will cost at least $880, while a window from Bieber® will cost almost twice as much.
www.paradigmwindows .com
Serious Windows: www.seriouswindows.com
Thermotech:
www.europeanwindows .com
Internorm:
Fortunately, Canadian windows with com-
www.internorm.com
parable performance specs cost roughly half
Optiwin:
the price of an Optiwin window.
www.optiwin-usa.com
Because of their positive latching hardware, casement, awning, and tilt-turn windows always outperform single- or double-hung windows.
Pazen ENERsign: www.quantumbuilder.com/ pazen
Silber: www.silberfenster.com
Unilux Ultratherm:
Martin Holladay is a contributing editor to Fine Homebuilding.
www.unilux.de
Do Europeans Really Make the Best Windows?
109
windows
3
Installing Replacement Windows BY MIKE GUERTIN
W
indows wear out before a house does. Sometimes the need for
If you find that your windows are costing you energy dollars, you can go one of two
replacement windows is obvious, such as
ways: Hire a full-service installer to measure,
when you encounter poorly functioning
order, and install new windows for you; or
single-pane sashes with weights. But even
buy and install them yourself. Replacement
windows with insulated glass become
windows are easy to order and quick to
difficult to operate, suffer from damaged
install, and you can save money if you
seals, or show signs of deterioration.
tackle this project yourself.
The good news is that replacement win-
along with greater levels of energy efficiency.
Evaluate Existing Windows
Window replacement could save you 5% to
The installation shown here took place in a
dows eliminate these problems, offering improved appearance and easier operation,
15% off your heating and cooling bills, but how much you’ll save depends on where you live (the potential is much higher in cold climates) and how inefficient your existing windows are. In some cases, air sealing and better insulation elsewhere in your house (see “Home Remedies for Energy Nosebleeds,” pp. 12–19) offer more bang for your energy buck. The best way to tell is with a home-energy audit, which will identify the biggest deficiencies in your home’s energy envelope (see “Every House Needs an Energy Audit,” pp. 4–11).
modest Cape that still had its original singleglazed, sash-weighted windows—a perfect candidate for replacement windows. I chose frame-and-sash replacement windows (also known as pocket windows) because the existing window jambs, sills, and trim were solid, and the siding was in good condition. Had the window frames been rotted or the siding in need of replacement, I would have had to install new-construction windows using the old rough openings. The budget didn’t allow for the extra labor to tackle full
Accurate measurements, thorough caulking, and proper installation will maximize your savings.
the interior and exterior trim to be removed
Choosing the Right Windows
and then reinstalled or replaced.
As a contractor, I order windows directly
window replacement, which would have required the siding to be stripped back, and
Finally, I didn’t want to disturb the home-
from more than a dozen manufacturers.
owners. Pocket windows are quick to install
Some are national, others regional, and a
and create little mess inside or out. On aver-
couple make their windows locally near
age, working alone, I can install one in less
where I work. National and regional manu-
than 30 minutes.
facturers generally don’t sell directly to
Installing Replacement Windows
111
Remove the Old Window and Prep the Opening
O
nce I’ve checked to make sure the window I ordered fits in the opening, I lay down a drop cloth to catch paint chips and debris. Stripping out old window sashes is easy, but I still work carefully because the windows can be fragile and the glass can break easily. I’d rather spend extra time in preparation than on cleanup.
Jamb
Outside blind stop Parting bead Inside sash stop
For the width, measure jamb to jamb.
1
Measure thrice to avoid ordering twice • Use the shortest of three horizontal measurements (See the drawing at near right). •U se the shortest of three vertical measurements. •D ouble-check for square by measuring the diagonal.
Watch for lead If your home was built before 1978, the old windows may have been painted with lead paint. Either have a professional test done to determine if lead paint is present (and the extent of it), or presume lead paint is present and follow lead-safe work practices. You can find out more from your local health department or the U.S. Environmental Protection Agency (www.epa.gov/lead).
112
Windows
2
For the height, measure from where the sash rests on the sill up to the head or top jamb. See “Accurate Measurements Are Critical,” p. 116.
4
3
Numbers are keyed to photos on facing page.
1. Remove sash stops. Cut the paint at the jamb joint with a utility knife; then drive a stiff paint scraper into the joint to pry off the stops. Be careful not to damage anything because the sash stops will be reused.
2. Carefully remove the sashes. Swing the inside sash out of the window opening, and cut the counterweight cords to free the sash. Remove the small parting bead between the sashes, and take out the outer sash the same way.
3. Remove the weights. Open the counterweight doors to remove the weights and cords; then unscrew the pulleys and remove them. Some installation guides suggest hammering the old pulleys into the jamb, but I disagree. The pulley holes make good view spots when installing insulation.
4. Insulate the cavity. Use an old parting bead to slide strips of batt insulation into the cavity. Don’t overstuff the cavity, or you’ll reduce the insulation’s R-value. Replace the counterweight doors, and scrape loose paint from the jamb and stops. Prime any bare wood on the jamb and sill to protect it from rot.
Installing Replacement Windows
113
Install the New Window with Expanders, Shims, and Screws
D
ifferent manufacturers have different details for securing and weathersealing their windows. However, they all have a sill expander of some type at the top and bottom, and rely on screws to secure the frame to the jamb.
2. The head expander fits against the head jamb. 3. Partially driven screws secure the window for centering.
1. Install the bottom sill expander. Use a Speed Square® to make a level reference line so that you can measure how much the sill slopes. Then use a utility knife to cut the bottom sill expander to fit snugly against the sill. Tap the expander into the window frame with the butt of a hammer handle.
2. Install the head expander. If the replacement window doesn’t overlap the head stop, you need to add the head expander that fits over the top of the window and fill the airspace with low-expanding foam or fiberglass insulation.
5. The inside sash stop is removed and reused as molding around the new window.
windows in standard sizes to fit the existing
have a retail store on site that will sell you
openings.
sale prices. You can also buy replacement windows
Windows
1. The bottom sill expander is cut to fit against the sloping sill.
homeowners, but many local fabricators windows at a small premium over whole-
114
4. Mounting screws in the window frame are used for the final adjustment.
I advise shopping around, but be sure you’re comparing equal products and services. Some companies’ standard features are
at a home center. If your house is 50 years
options that cost more from other fabrica-
old or less, you can find fairly good-quality
tors. Frame thickness and extrusion designs
3. Insert and center the window. Drive two mounting screws partway through the window frame and into the jambs to keep the window in place. Then use a small pry bar to get the frame centered, level, and plumb.
4. Secure the window. Insert shims between the window and the jamb as backing for mounting screws. Drive mounting screws in all the pilot holes. Sometimes these holes are concealed by sash stops or balance guards that can be slid out of the way or removed.
5. Replace the sash stops. The payoff for removing the old stops carefully is that they can be reused to finish the new window. Before installing the stops, I fill gaps between the window and the jamb with low-expanding foam, part of the weathersealing process (see the sidebar on p. 116).
can differ. Bargain windows might have
is good (20 years) and the price is reason-
lower-quality frames that require more time
able. Also, if problems arise, there’s someone
to shim and brace adequately for proper
local to call.
operation. If I have a choice, I use high-quality vinyl windows made locally. Although they might not be a popular name brand, the warranty Installing Replacement Windows
115
Get Maximum Value with a Good Weatherseal
I
f I’ve spent the money, time, and effort to replace a window, I want to get the best performance I possibly can. Proper weathersealing calls for spray foam and caulk.
Foam the gaps. Use low-expanding foam to fill gaps between the old jamb and the new window.
Accurate Measurements Are Critical
Writing measurements on a block of wood
I always take measurements myself, and if
Know How the Windows Are Sized
the sales rep comes out to help, I check that person’s work. The last thing I want is to show up on the morning of a whole-house window replacement and find out that someone else messed up the order. Most important is checking top, bottom, middle, and diagonally for square. The new window has to be sized for the shortest measurement (see the drawing on p. 112). I use a systematic approach with my own order sheet to note dimensions and location.
116
Windows
Caulk the stops. Apply exterior caulk to the blind stop before installing the swindow; then caulk all the exterior trim joints.
just doesn’t cut it. One wrong measurement, and you own a perfectly good window that doesn’t fit.
Replacement-window fabricators make units on a 1⁄4-in. basis, a 1⁄ 2-in. basis, or a combination of the two. This guideline forces you to order a unit smaller than anticipated when a dimension falls on a 1⁄ 8-in. increment, but undersizing a window is better than having it too tight. Window height is more forgiving than width due to the sill and head
Choose the Right Window
M
any manufacturers that make windows for new construction also make replacement windows. In addition to the factors listed below, you’ll need to consider cost and warranty details.
Style
Wood
Double-hung, single-hung, casement, awning, and other window styles are available.
• Requires painting • Compatible with historic houses
Glass
Fiberglass
The choices include different types of insulated glass, such as glass with heat-reflective coatings and gas-filled glass. You can also order windows with snap-in grilles or true divided lites.
• Stronger than vinyl and just as durable • Available with wood interior surfaces • Low maintenance • Usually more expensive than other types
Aluminum-clad Material The type of material used in the window determines its price, its durability, and its appearance. Here’s a quick tour:
• Durable exterior, wood interior • Many colors available • Aluminum can be painted
Vinyl-clad Vinyl • Usually less expensive than other types • Durable, low maintenance • Limited color choice
• Durable exterior • Wood or finished interior • Limited color choice
height sizing. If I have to choose between
Guarantee a Smooth, Safe Installation
leaving only 1⁄ 8 in. of wiggle room or having
Wherever I start, I move the furniture out
expanders, which is why many fabricators offer 1⁄4-in. width sizing and only 1⁄ 2-in.
5⁄ 8
in. to play with, I’ll take the bigger
measurement.
of the way for clear access to the window, and I cover the floor with a drop cloth to
Some window fabricators take orders
collect paint chips and debris. I always use
based on opening measurements, and they
a vacuum and a dust brush to clean out the
make the deductions to actual unit size from
windowsill and to clean up the floor when
information you supply. I never order this
I’m done working.
way because it does not account for out-ofsquare conditions. Make your own deductions from the measured opening, and order the actual window size (sometimes called
Mike Guertin (www.mikeguertin.com) is a builder, remodeling contractor, and writer in East Greenwich, R.I.
tip-to-tip size).
Installing Replacement Windows
117
hEAting AnD cooling
4
Is Your Heating System an Energy Beast? By DAVE yAtEs
T
he economy is down, fuel costs are up, and chances are that your heating
budget is already busted. You need to do something—but what? Only a few of us are ready to invest in geothermal or solar. The rest of us need to find the answer in the heating system we already have. For 70% of U.S. households, that system consists of a furnace that forces hot air through ducts; for 17%, it’s a heat pump; and for 11%, it’s a boiler that heats with water or steam radiators. The remaining 2% of homes use wood, coal, geothermal, solar, or other heating methods. When it comes to fuel, 58% of us use gas (either natural or propane), about 35% use electricity, and almost 7% use fuel oil. Your home might not have the most efficient heating system available, but there’s good news: You can tune up your current system so that it performs better, keeps you more comfortable, and doesn’t put as big of a dent in your wallet. The following can help. Although the topics might seem simple, they’re useful in diagnosing deficiencies. In fact, I usually end up fielding a lot
of these questions from homeowners based
source of air leaks. Because the access door
on their observations of how their heating
must be opened to service the equipment,
system is or isn’t working. Once you know
you want to use only tape or magnetic strips
where your system is falling down, it’s pos-
to seal gaps. Other spots to seal include filter
sible to boost it (and its efficiency) back up.
slots and openings for wiring. Last but not least, the accessible ductwork should be examined for leaks. Seal them with highquality tape, mastic, or sealant that’s compatible with the duct material and with exposure to surrounding air temperatures.
Q: Streaks of dirt are visible around the ceiling registers in our house. What’s causing them?
Q&A
A: Those streaks are tiny particles of soot
Q: I hear a whistling noise around the
blasted across the ceiling by air leaking
blower compartment of my furnace. What is
from around a register that isn’t connected
causing the noise? Should I be concerned?
properly. Think of your ceiling as the inner layer of a sandwich. If you had X-ray vision,
A: You’re hearing air leakage. All air
you’d see the duct boot resting on the attic
handlers (any device with a blower,
side of the ceiling with the register below,
including furnaces, heat pumps, and central
sandwiching the ceiling between them.
air) have two ducts: one for supply, the
If the boot isn’t firmly attached, you’re
other for return. I often find considerable
heating (or cooling) your attic—typically
air leakage at both connection points. If
unconditioned space—which means your
the blower is located in an unconditioned
energy dollars are being lost to the great
location (attic, crawlspace, or basement), it is
outdoors. The same goes for floor registers.
bleeding out heat, or Btu, on the supply side
In either case, the cure is the same: Remove
while pulling in unconditioned air that must
the register, use a sealant to close the gaps
be warmed (or cooled and dehumidified)
between the boot and the ceiling (or floor),
on the return side. This energy loss can
and add foam weatherstripping between the
add 10% or more to your heating and
ceiling (or floor) and the register to prevent
cooling bills.
air leakage.
You can fix these leaks by sealing the connection with sealant and/or top-grade mastic tape rated to withstand the area’s exposure. While you’re at it, check the air handler’s access door, another frequent
Is Your Heating System an Energy Beast?
119
Furnace Basics
F
urnaces use natural gas, propane, oil, or electricity, and are fired when a remote thermostat detects that the temperature in a room has fallen below a preset level. Once in operation, the burner fires in a combustion chamber and warms a heat exchanger (electric furnaces have coils much like a toaster). A blower pushes air over the heat exchanger, or coils, and hot air flows through a series of ducts and enters a home’s living
spaces through registers in the floors, walls, or ceiling. Ducts also supply return air to the furnace, and combustion gases exhaust through a chimney or direct-vent system.
homes. Prime spots for air leakage include furnace-to-duct connections 1. seams in the ductwork 2. and register assemblies 3. The author seals leaks with high-quality mastics, sealants, and tapes like the Hardcast® products shown above (www.hardcast.com).
seal air leaks, save money The most efficient forced hot-air systems are airtight, from the furnace to the registers. Those systems, however, are few and far between, especially in older
Supply air
Return air Trunk duct
Branch ducts
Supply air 2
1
Heat exchanger Exhaust 3
Duct boot
Sealant Ceiling register Disconnect switch Filter box Gas shutoff Blower
120
Heating and Cooling
Gas line
Foam weatherstripping
What Should I Expect from a Service Call?
Q: Our local oil company is offering a $29.95 service special. It seems like a bargain, but does heating equipment need to be serviced every year?
• Preliminary combustion analysis • Chimney inspection • Top of boiler removed and combustion chamber cleaned • Soot vacuumed from all surfaces • Oil filter replaced • Oil-burner nozzle replaced • Reassembly; draft in flue and over burner checked; boiler operation tested • Final combustion analysis
A: Just as people should get an annual physical, all heating equipment should receive an annual checkup to maintain peak performance and to keep the home’s occupants safe. Part of the service is a test for proper combustion using an analyzer that provides CO (carbon monoxide), O2 (excess oxygen), and CO2 (carbon dioxide) levels, as well as net stack (exhaust) temperature. You should ask for a copy of this test, or combustion analysis. While the internal surfaces of some gas appliances don’t need to be vacuumed (unlike oil units), regular maintenance is particularly important for newer highefficiency models. Also, in all units, the
Q: Our ductwork is located in the attic.
chimney or venting should be inspected
There doesn’t seem to be as much warm air
periodically to make sure it’s not obstructed.
blowing from the registers as there used to
Dirty heat exchangers in oil burners rob
be. Is that my imagination?
efficiency, which results in increased fuel usage. A layer of soot just 1⁄16 in. thick
A: Ductwork that travels through
reduces operating efficiency by 10%.
unconditioned spaces (basements,
That said, it’s not physically possible to
crawlspaces, garages, and attics) needs to
clean and tune up an oil-burning appliance
be well insulated. Uninsulated ducts waste
properly for $29.95. Companies offering
gobs of energy and create drafts as chilled
prices that low often pay technicians a flat
air spills out of ceiling registers; it’s hard to
rate for each call they make; the more they
believe how noticeable this is until you’ve
fit into a day, the more profitable it is for
felt it firsthand. Newer codes require R-8
them—at your expense. I often see those fur-
minimum insulation on ducts, but on
naces six to eight years later, when they’re
older flex and duct-board systems, it can
malfunctioning. So accept the fact that if it
be as low as R-2.5. Before you consider
sounds too good to be true, it probably is,
more insulation, however, remember that
and call in a professional technician you can
insulation can hide the real problem: air
trust at a believable price. Is Your Heating System an Energy Beast?
121
Duct board
Insulation helps, too. once all ducts are airsealed, use insulation to limit heat loss. owens corning makes insulated rigid ducts, insulated flexible duct wrap, and foil-faced insulation that can be used to wrap existing ducts (www.owenscorning.com).
Flexible duct insulation sleeve Duct wrap
leakage. According to the Department of
with mastic can result in substantial fuel
Energy, you could be losing 40% of the
savings. Once the leaks are sealed, add more
heat through duct leaks. A home-energy
insulation around the ducts, either blown-
audit that includes a duct-pressure test
in, loose fill, fiberglass batt, or a duct wrap,
can identify those leaks; sealing them
as seen above.
Heat-Pump Basics
A
ir-to-air heat pumps use pressurized Freon® gas to absorb heat from the air outside and transfer it to your home. When the thermostat calls for heating, Freon is pressurized, it condenses, and then it turns to hot liquid. A blower forces air across warm Freonfilled coils and through a system of ducts; warm air Fan
Disconnect box
is distributed through registers in the floors, walls, and ceiling. At the same time, a fan in the condenser sends cold air outside. You can reverse the cycle for cooling in the summer. (Ground-source heat pumps use a water/glycol mixture to exchange heat energy with the earth.) Branch duct
Trunk duct
INDOOR UNIT
Damper Return air
Coils
Freon lines Coils OUTDOOR COMPRESSOR
122
Heating and Cooling
Filter box Blower
DAMPERS ADJUST AIRFLOW. In a forced hot-air system, you sometimes can adjust the inline dampers to increase or decrease airflow to a specific part of the house. When the lever is in line with the duct, the damper is fully open. When the lever is perpendicular, it’s closed.
While adjusting airflow this way could improve comfort, it doesn’t help the system to perform better. To do that, you need to call in a pro. A good HVAC contractor uses a nationally approved design program to size an entire duct system properly. Ask the contractor to show you how he or she does the design work, and ask questions. The fix can range from a few simple adjustments to installing a mini-split inverter heat pump in the affected areas to ripping out everything and starting over, costing from a couple of hundred dollars to several thousand.
Q: The temperatures upstairs and downstairs are uneven; some rooms are colder or hotter than others. What’s causing this problem? Can it be fixed?
Q: I hear a lot about tuning up furnaces, but how can I boost the efficiency of my heat pump?
A: Like furnaces and boilers, your heat
A: You’re likely describing an out-of-
pump should be serviced annually. Cleaning
balance duct system. If a forced-air system
the coils and changing the filter can increase
isn’t ducted properly, the flow of supply
the heat pump’s efficiency by up to 10%.
and return air is unbalanced, resulting, for
Heat pumps are rated in SEER for cooling
example, in a ground floor that doesn’t
efficiency and HSPF or COP for heating
stay warm in heating season or a second
efficiency. (See “Say What?” on p. 124.)
floor that’s not sufficiently cooled in AC
The higher the numbers, the higher the
season. Sometimes it’s due to poor duct
efficiency and the lower the operating costs.
design; other times it occurs when air-
If your heat pump operates below 13 SEER
conditioning is added to a heating system
and 6.5 HSPF (the current minimum stan-
without re-evaluating and possibly resizing
dards set by the federal government), you
the ductwork.
should plan to replace it. When you do, ask
If you have problems with individual
for a 410A refrigerant-based system (Carrier®
rooms and you’ve made sure all the ducts
calls it Puron®). The 410A-based
are connected properly (believe me, I’ve seen
systems are a bit more efficient
my share of ducts to nowhere), you might
and a bit more expensive,
be able to adjust the dampers and guide a
but the R-22 refrigerant
little more (or less) air to those areas. Damp-
currently in use is being
ers are normally located within the first
phased out. As a result,
few feet of each branch, or takeoff, and are
it’s unlikely to be available
adjusted by turning an external lever. Gener-
when new equipment wears out.
ally, when the lever is in line with the duct,
With today’s fuel costs escalating, you
the damper is fully open. Airflow also can be
might also want to consider a hybrid heat-
regulated somewhat at the register if it’s an
ing system, wherein a fossil-fuel furnace is
adjustable model; however, that can create
coupled with a high-efficiency heat pump,
an objectionable noise as air rushes past the
allowing you to choose whichever system is
louvers.
least expensive to operate at specific times.
Is Your Heating System an Energy Beast?
123
These setups often use automatic controls
Q: I keep hearing about “modulating”
that seamlessly switch from one system
technology in furnaces and boilers.
to the other based on the internal
What’s that?
programming.
A: Traditionally, heating equipment operates on one speed: Either it’s on, or
Say What?
A
sk a heating contractor for advice about your home’s systems, and you might get an answer that sounds like it’s in a foreign language. Contractors sometimes forget that consumers aren’t familiar with the lingo that’s second nature among pros. Here, we translate a few of the terms common to the heating-and-cooling industry.
AFUE: Annual Fuel Utilization Efficiency An indicator of how well gas- and oil-fired equipment uses energy. Translates easily to dollars: A 98%efficient unit transfers 98¢ of each energy dollar from fuel to home.
BTU: British Thermal Unit The amount of energy required to raise 1 lb. of water 1°F. In terms of electricity, 1 watt equals 3.4129 Btu. MBH stands for 1,000 Btu per hour.
up, it produces the same amount of Btu whether it’s trying to raise the temperature of a house 2°F or 20°F, and whether the air outside is -5°F or 50°F. But a number of new, high-efficiency stepped-input (“hi-lo fire”) furnaces can operate at two levels: low input or high input, with a lower or higher fan speed. Because the low-input level can be used when outdoor air temperatures are relatively moderate (roughly 70% of the heating season for many of us), modulating equipment promises fuel savings of 30% or more. When the heat-demand load exceeds the “lo-fire” output, the furnace control steps on the gas to meet demand. Modulation technology has been limited to boilers—until now. York International’s
COP: Coefficient of Performance
recently released Affinity 33 is the industry’s
The ratio of the energy input of a heating or cooling appliance to its heating or cooling output. The higher the COP, the more efficient the system.
first truly modulating gas furnace that uses
EER: Energy-Efficiency ratio
determine how hard it needs to run to meet
Overall efficiency related to energy usage. It’s calculated by dividing the net Btu output by the wattage used.
a home’s heat loss (from 35% to 100% in
HSPF: Heating Seasonal Performance Factor
and the manufacturer claims 98% thermal
Indicates the heating efficiency of heat pumps. The higher the HSPF, the lower the cost to operate the equipment.
MERV: Minimum Efficiency Reporting Value Measures efficiency of air filters. The higher the MERV number, the better an air filter works to capture airborne contaminants.
SEER: Seasonal Energy-Efficiency Ratio The cooling efficiency of an air conditioner or a heat pump. The higher the SEER number, the lower the cost to operate the equipment.
124
it’s off. The minute a furnace or boiler fires
Heating and Cooling
outdoor reset, which adjusts the system based on the air temperature outside, to
1% increments). Both the burner and the blower modulate as a team to maximize Btu, efficiency.
A furnace first. The York® Affinity™ 33 is the industry’s first modulating gas furnace and boasts 98% efficiency (www.york.com).
Modulation is an almost universal feature found on high-efficiency condensing boil-
High-grade your hydronics. thermostatic radiator valves fine-tune hydronic heating systems by controlling temperatures in individual rooms. set the dial to raise the temperature in one room and lower it in another (www.danfoss.com).
ers. Here, too, you’ll find products that can achieve 98% thermal efficiency. Virtually all these high-efficiency products use outdoor reset to achieve superior comfort and efficiency.
Q: We’re not ready to replace our heating equipment right now. What can we do to improve our comfort and reduce fuel bills?
If you have a central system that’s not zoned, a motorized damper system can de-
A: If you’ve performed the fixes I already
liver heat where you need it most. Multiple
mentioned and you’re still uncomfortable
dampers can be daisy-chained so that several
(or breaking open the piggy bank to meet
rooms operate as one zone. One caution: It’s
fuel costs), you might consider fine-tuning
important to have a good professional do
your system with an auxiliary appliance.
this work.
One option is spot-treating one or more
If you have a hydronic system, you can
rooms with high-efficiency mini-split heat
fine-tune the zones with thermostatic ra-
pumps. With efficiencies topping out at
diator valves, which can be installed in
26 SEER and 12 HSPF, these ultraquiet heat
every room except where the thermostat is
pumps give you the option of conditioning
located. Once you set the dial, the valves
just the space you’re occupying while letting
open or close automatically based on the
the rest of the home’s mechanical systems
room’s temperature. They’re a good solution
hibernate. They’re basically self-contained
in rooms that are chronically overheated or
units with supply tubes for refrigerant
that are seldom used.
running through the wall. The best ones
In an uncertain economy, investing in
use inverter (variable-speed) technology,
energy—that is, the energy you use in your
allowing the units to sip only as much
own home—could be your wisest move.
electricity as they need to maintain comfort.
Your ROI (return on investment) begins the
If you have a hot-air system, adding hu-
second you start using the equipment and
midification can increase comfort while let-
can well exceed anything the stock market
ting you reduce the temperature by several
can yield. You’ll add value to your largest in-
degrees. You can plug in a freestanding unit
vestment (your home), you’ll be more com-
or have a pro connect one to your furnace
fortable, and you’ll get to keep more of your
for $600 or more.
hard-earned money.
Q: What separates low-efficiency heating A damper with horsepower. motorized dampers allow for controlled airflow through ducts from remote locations and can create heating zones in a formerly one-zone house (www.aprilaire .com).
systems from high-efficiency models?
A: One difference is the way the unit is vented. A 78%-efficient furnace (or boiler) vents into a chimney and uses the home’s interior air for combustion. New 92%-efficient models are designed for sealed combustion. A direct venting setup draws outdoor combustion air.
Is Your Heating System an Energy Beast?
125
Boiler Basics
B
oilers heat water with gas, propane, oil, or electricity, and the water heats the home through a hydronic delivery system that can include baseboard fin-and-tube radiators, steam radiators, or in-floor radiant heating. When the thermostat fires the boiler, fuel burns in a combustion chamber, and warm water is pumped through a closed circuit of tubing. (Electric boilers have direct-immersion heating elements.) The water can get as warm as 180°F, depending on the system’s design. Because hot water expands, a pressure gauge and a relief valve prevent the system from failing due to excess water pressure. Combustion gases exit the house through a chimney or a direct-vent system.
Return
Chimney
Supply Circulator pump
Exhaust flue
Cleanout door
Aquastat
Oil filter Combustion chamber
Exhaust pipe Fuel line
Oil burner
Exhaust
Drain
Combustion-air supply 12 in. min. Boiler or furnace
DIRECT VENTING
126
Heating and Cooling
Air intake Snow line
Outside wall
Chimney-vented heating equipment continuously drafts heated air out of the house and strips away some of the Btu produced when the furnace is operating. There’s also a hidden energy cost: air infiltration. Whenever its burner fires, the chimney-vented unit draws in warm room air to support combustion—air that must be replaced by cold outside air drawn through cracks and gaps in the home’s shell. Eliminate that draw with a sealed-combustion model, and your fuel bills could fall by 30% or more. Cost also separates the top performers from the rest. But the difference in price between 78%- and 95%-efficient gas-fired furnaces has narrowed considerably, to about $1,500 for the equipment and installation costs. If your system burns oil, you have fewer choices, and the price gap is wider (about $4,000). But with ever-shifting oil prices, it’s easier to justify the extra expenditure.
Q: My furnace still works, but my heating bills are sky-high. Should I think about getting a new one?
A: Given today’s rapidly escalating fuel prices, you really can’t afford not to consider upgrading to a new high-efficiency furnace. Older furnaces were constructed with durability, not efficiency, in mind. Trimming 20% to 70% off your fuel bills is a realistic
front costs. But with the rise in fuel prices
expectation when you upgrade to high-
and the anticipated 20- to 30-year life span
performance equipment.
of a furnace, the increased purchase price
Your existing furnace most likely has a 60% to 78% efficiency rating, which was
pales by comparison to the fuel costs saved over time.
once considered respectable. The current federally mandated minimum efficiency for furnaces is 80%, but there are models—
Dave Yates owns and operates F.W. Behler Inc., a mechanical-contracting firm in York, Pa.
hundreds of them—that operate above 92% and qualify for Energy Star rebates. There are even a few that can achieve 98% efficiency by using a feature called “outdoor reset,” which modulates both the blower speed and the burner’s fuel input. As you might expect, the better the efficiency, the higher the up-
Is Your Heating System an Energy Beast?
127
HEATING AND COOLING
4
Finding the Sweet Spot: Siting a Home for Energy Efficiency house. The ancient Greeks oriented their town grids to receive winter sun and summer shade. The Anasazi Indians located their dwellings beneath cliff overhangs to take advantage of natural shading. Early American settlers oriented and configured their saltbox houses to minimize the cold northern facade and to maximize the warm southern facade. Regrettably, the siting lore known to our ancestors has practically disappeared because of central-heating and -cooling systems. That’s too bad, because a house’s energy efficiency, comfort, and marketability are all affected by its siting. A house that’s sited to take advantage of the sun, the wind, and the topography costs less to heat and cool, and lets you enjoy indoors and outdoors longer,
BY M. JOE NUMBERS
two strong selling points. In the site-design classes I used to teach,
A
we divided solar-siting strategies into three rchitecture professors love a good
categories: orientation, or which way the
riddle. Here’s one: How do ancient
house faces; location, or where the house
Greek town grids, Anasazi Indian pueblos,
sits; and configuration, or how it’s shaped.
and New England saltbox houses differ from
Figuring out the best orientation, location,
most residential construction today? Give
and configuration requires a little knowledge
up? Each culture understood how to site a
of local climatic conditions and an analysis
of the site and its surroundings. Here, I’ll
Lots of related strategies make a true-
discuss what to look for and where to find
south orientation more effective. One is to
the information you need to reap the ben-
reduce openings (i.e., windows and doors),
efits of a properly sited house.
especially on the north side of the house, because doors and windows conduct more
Long Side Faces South
heat than a well-insulated wall. In cold cli-
When siting a house, the most effective
facing walls should be openings. In warmer
strategy you can use is to orient the building
climates, you can get away with slightly
with the long side aligned on the east-west
more openings as long as the house is well
axis. This orientation places the long side
insulated.
of the building where it can be reached and
mates, only about 5% to 10% of non-south-
On south elevations, increase openings
heated by the low-angle rays of the winter
for winter solar gain, but shade them during
sun. Conversely, it places the short sides of
summer months. Deciduous trees provide
the building to the east and west to mini-
summer shading, as do awnings. You can
mize solar gains during the overheated peri-
also build overhangs, but they shouldn’t be
ods of summer.
so deep that they block the sun in winter
Your house doesn’t have to be exactly on the east-west axis; somewhere within
(see the drawing on p. 131). To figure out the optimal depth for over-
15 degrees of this axis is fine. What’s more
hangs in your area, use the shade-line-factor
important is that the house is oriented
formula: The depth of an overhang equals
toward true south, not magnetic south.
the height from the bottom of a window
Compass needles point to magnetic north,
to its overhang divided by the shade-line
which deviates from true north by as much
factor. This number varies with latitude, so
as 20 degrees. The difference between mag-
you’ll need to know your location’s geo-
netic north and true north is declination,
graphic latitude to choose the right shade-
and it varies across the United States (see
line factor. Most maps of the United States
the sidebar on pp. 130–131). Information on
and most state maps show latitude.
declination can be found on U.S. Geological
Another way to make a southern expo-
Survey topological maps or the NOAA web-
sure work harder for you is to coordinate
site (http://www.ngdc.noaa.gov/geomag/
the floor plan with the house’s orientation.
geomag.shtml).
Locate public living spaces, such as the liv-
Once you know your area’s declination
ing room, the dining room, the kitchen, and
angle, it’s a matter of spinning the dial on
such, to the south side of the house, where
a compass. For example, in Boise, Idaho,
they will receive light and warmth through-
the declination angle is approximately
out the year. Locate private and unoccupied
14 degrees east. Line up a compass on mag-
rooms—bedrooms, utility rooms, storage
netic north, then rotate the dial until the
rooms, etc.—to the north, where they will
needle is pointing to 14 degrees east of the
act as insulating buffers for the home’s
north mark on the dial; now the dial mark-
public spaces (see the floor plan on p. 130).
ings (not the needle) point to true north.
These buffer spaces serve as a form of insulation (particularly if they can be closed off
Finding the Sweet Spot: Siting a Home for Energy Ef ficiency
129
Orient the House to the Sun
P
lacing the long side of a house along the eastHallway west axis exposes the south elevation to yearBathroom round light and warmth. In summer, this orientation minimizes overheating on the short east and west elevations. Grouping private and unoccupied spaces on the north side of the house, where they Bedroom act as insulators for the south-facing public rooms, maximizes the benefit of southern exposure. North
Garage Kitchen
Bedroom Living room
Bedroom
Finding True North At the bottom margin of U.S. Geological Survey maps, there are three north bearings: magnetic north, true north, and grid north. Magnetic north is compass-needle north, but it’s not helpful for solar siting, which calls for true north, indicated by the star. The difference between these bearings is the declination, in this case, 13.5 degrees.
Public areas face southward.
★ MN 13.5° 240 MILS
Dining room
GN 1°07’ 20 MILS
from the rest of the house), much like the
There, the house is not exposed to increased
closed airspace in a thermos keeps the cold
wind velocities at the ridge or to subsiding
air outside from cooling the warm liquid
cold air that settles at the valley bottom.
inside.
In hot, humid climates—the Gulf Coast states and the Southeast—ridges generally
Hillside Lots Are Cooler, So Plan Accordingly
provide the most exposure to year-round
Donald Trump once said that the three most
doors and windows at night and by closing
important considerations when buying real estate are location, location, and location. I doubt that he was referring to the potential for lower heating and cooling costs, but a house’s location on a piece of land can make it less expensive to heat and cool. If you’re considering building on a hillside, for example, locate the house according to its most appropriate zone. In cold or temperate climates, it’s best to locate a house midway between the ridge and the valley. 130
Heating and Cooling
cooling breezes. In hot, arid climates such as the Desert Southwest, valley floors tend to collect cold air overnight that helps to cool a house. You can trap this cold air by opening them during the day. Building on a south-facing slope, or aspect, of a landform increases the exposure of the house and surrounding grounds to the low-angle rays of the sun during the winter. In cold and temperate climates especially, you should avoid north-facing aspects whenever possible. You should also take a good look at the adjacent area to the south of the building
Window Height ÷ Shade Factor = The Right Overhang An effective window overhang shades summer sun but allows for winter-sun penetration. The overhang’s depth depends on the shade-line factor, determined by the house’s geographic latitude and the direction the window faces. See the chart below, and also measure the overhang’s height above the windowsill; then plug those numbers into the equation above to get the overhang’s ideal depth.
Midsummer sun
Midfall/ spring sun Depth
Midwinter sun
SHADE-LINE FACTORS Direction Window Faces
Latitude in Degrees 25
30
35
40
45
50
55
East
0.8
0.8
0.8
0.8
0.8
0.8
0.8
Southeast
1.9
1.6
1.4
1.3
1.1
1.0
0.9
South
10.1
5.4
3.6
2.6
2.0
1.7
1.4
Southwest
1.9
1.6
1.4
1.3
1.1
1.0
0.8
West
0.8
0.8
0.8
0.8
0.8
0.8
0.8
site. Avoid building on areas that will be
strategies provide additional, permanent in-
shaded during winter by tall buildings, co-
sulation against both winter winds and sum-
niferous trees, or landforms (ridges, etc.).
mer overheating.
If you’re in a cold or temperate climate,
Earth-berming strategies require careful
where it’s best to build midway along the
detailing to prevent water damage to the
hillside rather than at the ridge or in the
structure. They are generally more expen-
valley, you should study the contours of the
sive than typical aboveground construction.
hillside. Any natural drainages or depres-
When properly done, however, earth berm-
sions in the topography are poor choices for
ing provides long-term, low-maintenance
a building site (see the drawing on p. 132). A
energy savings.
natural drainage or depression channels cold
Height
If you are not familiar with earth-berming
air down the hillside. This cold air collects
strategies but have a site that is suitable,
behind obstructions to its natural flow, so a
consult an architect or a designer experi-
house should be built away from these cold-
enced in this type of construction.
air flows. If you simply cannot follow this strategy, use evergreen vegetation or solid fencing to divert cold air around and away from the house. Whenever possible, recess the north, east, and west sides of the house into the natural slope of the site, or pile soil against the house on these sides. These earth-berming
Make the Wind Work for You Generally, summer and winter winds come from different directions. It’s usually possible to divert winter winds and to channel Finding the Sweet Spot: Siting a Home for Energy Ef ficiency
131
summer breezes by carefully locating the
cess of evaporation cools summer breezes
house in relation to its surroundings. Check
as they pass over water bodies. These water
with your local airport, meteorological sta-
bodies don’t have to be big to have an effect.
tion, or state energy office to determine the
Locate the house to catch prevailing sum-
prevailing summer- and winter-wind direc-
mertime breezes coming off lakes, ponds,
tions for your area. Also, this data can be
rivers, and even streams.
obtained from the U.S. Department of Com-
Conversely, in cool and temperate cli-
merce National Climatic Center in Asheville,
mates, avoid locations near bodies of water
N.C. (www.ncdc.noaa.gov/oa/climate/
on the lee side of prevailing winter winds. In
climatedata.html).
other words, if winter winds generally blow
Study the adjacent topography, trees, and buildings during your initial site inspection. Look for those existing conditions that can
from the north, avoid sites at the south end of a water body. Water isn’t the only medium that induces
block or divert cold winter winds around the
cold winter winds. Landforms, vegetation,
building site. Locate the house in these lee-
and buildings all can increase wind veloci-
side areas (see the top drawing on p. 134).
ties because of a phenomenon called the
In warm or humid climates, place the house in a part of the site that maximizes summer ventilation. For example, the pro-
Venturi effect. The Venturi effect occurs when any moving medium—in this case air—squeezes
Build at an Elevation to Match the Climate On a hilly site, locate your house on the part of the slope that offers the best conditions for your climate. Ridges are subject to year-round breezes and lower humidity. Valleys collect cool air at night. Midway along a slope, houses are protected from winds at the ridge and from cold air at the valley.
COLD AIR FLOWS DOWNHILL Cold air is heavier than warm air, so at night, cold air travels downhill along natural drainages and depressions.
Cold Temperate Cold air Hot, arid
Hot, humid
In hot, humid climates, ridges offer more exposure to cool summer breezes. In cold or temperate climates, build away from cold-air flows. In hot, arid climates, valleys collect cold air overnight that helps to cool a house.
132
Heating and Cooling
Natural drainage
Depression
House is located on a knoll to avoid cold air.
through a constricted opening. To maintain
through the building skin than narrow or
a constant volume of air passing through
elongated shapes.
the opening, the wind velocity increases
As a general rule for siting a house in cold
accordingly. That’s why it’s so windy at the
regions, the long dimension of the house
base of tall buildings.
should be approximately 1.1 to 1.3 times
Keep away from topography, adjacent
the length of the short side. This proportion
buildings, or vegetation that funnels cold
yields a high ratio of heated interior space
winter winds at increased velocities. If you
to exterior skin. Remember that the longer
do have a problem because of the Venturi ef-
side of the house is oriented along the east-
fect, you can position adjacent outbuildings
west axis.
and evergreen trees and shrubs where they will block winter winds. Conversely, locate the house (and any
For temperate climates, the configuration is not as important. There is less environmental stress on the building skin, so
new vegetation, fences, or outbuildings) to
the designer has more freedom in terms of
take advantage of increased wind velocities
building configuration. For this region, a
created by the Venturi effect during summer
ratio between 1.6:1 and 2.4:1 provides good
months (see the bottom drawing on p. 134).
energy performance.
Use buildings and vegetation to channel
In hot, arid climates, the environmental
summertime breezes into the house. As a
stresses are greater, so buildings should be
rule, try to orient the house within 30 de-
shaped similarly to cold-climate configura-
grees of perpendicular to prevailing summer
tions. A ratio somewhere between 1.3:1 and
winds to maximize their cooling effects.
1.6:1 is the most energy-conserving for hot,
If solar orientation and siting for wind are at cross-purposes (that is, if optimum solar
arid climates. In warm or humid climates, elongated
orientation is perpendicular to optimum sit-
shapes with openings on the long sides al-
ing for wind), then solar orientation should
low for cross ventilation. Generally, ratios
take precedence because it has a greater cu-
in the range of 1.7:1 to 3.0:1 are preferred.
mulative effect on the heating and cooling
When these elongated plans are oriented
of a house.
with the long side on the east-west axis, summer overheating at the short east and
House Shape Should Fit the Climate
west elevations is avoided.
Are you familiar with the aluminum heat-
exterior-wall surface is exposed to wind,
radiating fins that can be slipped over hotwater pipes in a basement? They’re supposed to turn hot-water pipes into heating elements to heat the basement space. The principle behind the fins is that they increase the heated surface area so that more heat escapes from the pipe with the fins than from the bare pipe. The same principle applies to a house’s shape, or configuration. As a house’s surface area increases, so does the amount of heat it loses. To hold on to the heat, configure the
Try to keep corners on the house to a minimum. Unnecessary corners mean more which increases heating loads on the house. Regardless of wind direction and particularly in areas where wind direction changes frequently, a good overall strategy is to use a compact, low-profile house design. Avoid tall facades and roof designs that block or trap wind. For example, a tall, broad gable is less aerodynamic than a hip roof, which allows for smoother airflow around and over the house. Orient the narrowest dimension of the house into prevailing winter winds to minimize wind exposure.
house so that it is relatively compact. Compact shapes, such as cubes, lose less heat Finding the Sweet Spot: Siting a Home for Energy Ef ficiency
133
Control Exposure to the Wind Use plants and outbuildings to direct prevailing summer breezes into the house and to divert prevailing winter winds away from the house. Once you know the direction of prevailing winter winds, choose a site where topography, vegetation, and other buildings offer protection.
Prevailing winter winds
Lee-side protection
Backwash exposure
Windward exposure
Garage Evergreen trees and a garage shelter the house from prevailing winter winds. House
Prevailing summer breezes are funneled by deciduous trees into the house at increased velocity due to the Venturi effect.
Configure the house and its surroundings to funnel or channel cooling summer
into window openings. On the other hand,
breezes into windows and screened-door
locate and configure the house to avoid
openings. For example, you can orient
channeling any cold winter winds into
breezeways and window openings to accept
doors and windows.
these summer winds. Use roof overhangs to
134
Heating and Cooling
trap incoming breezes and channel them
Learn More about the Principles of Siting a House
Although out of print, another good resource available at used-book stores and libraries is Climatic Building Design: EnergyEfficient Building Principles and Practice by
For more information on siting principles, additional detailing, and solar-design strategies for houses, as well as the mathematical formulas required to analyze these strategies for their potential energy savings, check out the second edition of Sun, Wind
Donald Watson and Kenneth Labs (McGrawHill, 1993). Both books contain a wealth of helpful charts, meteorological data, and examples of solar siting and building design. M. Joe Numbers is an architect with Gile-Buck & Associates in Boise, Idaho.
& Light: Architectural Design Strategies by G. Z. Brown and Mark DeKay (John Wiley & Sons Inc., 2000).
Guidelines for Shaping an Energy-Efficient House A house with a high ratio of interior space to exterior surface costs less to heat and cool. In very cold or very hot areas, then, houses should be more square than rectangular. In temperate areas, shape is not critical, but in humid areas, a long, narrow house allows for cross ventilation. In cold climates, an energyefficient house has a long side that is no more than 1.3 times the length of the short side. Cold
In temperate climates, a house’s long side should be 1.6 to 2.4 times the length of its short side. Temperate Hot, humid Hot, arid
In hot, arid climates, a house whose long side is 1.3 to 1.6 times the length of its short side offers the best ratio of cool indoor space to exterior wall area.
In hot, humid climates, a house whose long side is 1.7 to 3.0 times the length of its short side promotes cross ventilation.
Finding the Sweet Spot: Siting a Home for Energy Ef ficiency
135
heating and cooling
4
Cool Design for a Comfortable Home By Sophie Piesse
I
live in North Carolina, and I love the look on people’s faces when I tell them
that I haven’t turned on my first-floor airconditioning in 10 years. There’s always a pause, and then they lift their jaw off the floor and ask me, “Really? How?” As an architect who designs new homes, renovations, and additions, I encourage my clients to explore options for passive heating and cooling and energy-smart design before we ever look at mechanically assisted options. To make your house truly energyefficient, you must design it with the goal of using as little energy as possible. It’s great when people get excited about adding solar hot-water panels and photovoltaic systems, but before exploring any of that, you should first look at how you can design your new home or alter your existing home to reduce its energy needs. When your house naturally needs less energy, you can use smaller mechanical systems to support it. This saves
Passive in practice. The author’s house demonstrates passivecooling strategies that include east-west orientation, overhangs formed both by eaves and a second-floor balcony, and a vertical design that promotes good ventilation.
money both up front and in the long run.
Passive Solar vs. Passive Cooling
1. Face the Sun, and Shade the Glass
When we talk about passive-solar design,
The first step to passively cooling your home
we often focus on how it can help to heat
is to stop the heat before it ever comes in.
your home. Passive-cooling design is really
This is where siting and shading come into
the opposite side of the same coin, using
play. When designing a new house, you
the properties of the sun to promote cooling
have a great opportunity to take advantage
rather than heating.
of orientation, but it’s also important (and
Passive-solar design can cut heating bills, but in the South and in many areas of the country, keeping your house cool in the
often ignored) when adding to or altering an existing house. Here in the Northern Hemisphere, a
summer is a bigger concern. Here, passive-
house that faces south is optimal because
cooling strategies become more important,
that is where the sun comes from. Southern
and more economical. These simple design
orientation makes it easier to control the
elements can save you hundreds of dollars
amount of sunlight that enters the house.
every year in energy bills and also make
Even in the South, designing a house with
your house more comfortable to live in.
a long east-west axis (minimal exposure to
Passive cooling refers to nonmechani-
the east and west, maximum exposure on
cal ways of cooling your home. It focuses
the north and south) allows you to take the
on orientation and shading, air movement,
best advantage of the sun. This strategy is
thermal mass, and a tight building envelope.
associated with passive heating, but passive
All these strategies can be complemented by
cooling also benefits from the same type
mechanical means—from air-conditioning
of siting.
to ceiling fans—but these passive elements can also work successfully on their own. While the potential for saving energy with any design-focused strategy is greatest
When the house faces south, simple overhangs can shade it for the hottest part of the day, generally from 10 a.m. to 2 p.m. The
Degrees of shade. Pergolas can be designed specifically to admit or block sunlight at various times of the day or year, making them an especially versatile type of shade structure.
when you’re planning a new house, several of the techniques I describe can be used when renovating or adding to an existing home. You may not be able to pick up your house and face it in another direction, but you can add shade structures and window overhangs, relocate window openings, and mitigate nearby “heat islands” (such as a driveway baking in the midday sun), all of which enhance your home’s ability to maintain a comfortable temperature with less mechanical intervention. So let’s take a look at how your house can work with the environment. By designing your home to work with nature instead of against it, you can benefit from lower energy bills, better daylighting, and greater indoor comfort.
Cool Design for a Comfor table Home
137
Orientation
House Maximum glazing, this side 2 p.m. sun
10 a.m. sun South
West is best. placing a screened porch on the west side of the house minimizes late-afternoon heat gain in the summer and leaves the south side unobstructed so that it can collect as much solar gain in the winter as possible. This porch runs along the entire west side of the house, adding living space and providing cross breezes to the living room and master bedroom through two French doors.
or west sides of the house to provide protection from the low sun. By keeping the porch away from the south side, you’re not compromising the daylighting and heat benefits available from the south. Other options for shading include pergolas, screens, and plantings. Pergolas, in particular, are a great op-
overhangs need to be sized correctly so that
tion; they not only shade the house but also
they not only block the sun at its hottest,
create an outdoor space to enjoy. Growing
but also allow light and warmth inside when
vines on pergolas can increase the structure’s
the sun’s angle changes in the winter, and in
shading ability. Be sure to select deciduous
the mornings and evenings. Because this fac-
varieties; they’ll provide maximum shade
tor is based on the latitude where you live,
when fully leafed out in summer, but won’t
the proper size of the overhang varies from
block sunlight in winter.
region to region. The latitude where I live in North Carolina is 35 degrees north. That
visually and also can help to keep it cool.
means the sun rises to 78 degrees above the
Plant larger plants and trees to the east and
horizon in summer and 30 degrees in winter.
west for shade. Plants absorb heat, lowering
Here, a 2-ft. overhang is optimal because it
the temperature of air moving over them,
blocks the hottest summer sun but lets the
so air that enters your house after traveling
low winter sun shine inside (see the drawing
over the garden is actually cooler than the
on the facing page). To determine the opti-
surrounding air. Low bushes and plantings
mal overhang where you live, see the chart
also help by minimizing hard surfaces that
on p. 131.
absorb heat and radiate it back toward the
In the early morning and at sunset, when
walkways, and patios—work against any
it’s harder to keep heat out of the house,
passive-cooling measures you might have
even with overhangs. You can minimize this
taken, particularly if your house has win-
morning and evening heat gain by minimiz-
dows that are low to the ground and capture
ing the number of windows on the east and
the hot air that radiates off these surfaces.
west sides of the house.
Lower roofs on porches or bump-outs, espe-
Another strategy is to locate shading de-
Heating and Cooling
house. These “heat islands”—driveways,
the summer sun is much lower in the sky,
vices, such as a screened porch, on the east
138
Landscaping complements your house
cially those covered with asphalt shingles, radiate heat that can enter the house
through windows open above them. In these situations, casement windows are the most
Overhangs
effective at guiding cool breezes into the house, and they allow less of the heat radiating off the roof to gain access inside. Avoid awning windows, which channel rising hot air into the house.
Based on the sun angle where I live in North Carolina, a 2-ft. overhang is optimal.
Summer sun
Enhancing passive cooling through orientation and siting is easiest when designing a new home. But installation of window over-
2 ft.
hangs and the use of plantings and attached
Winter sun
structures can boost the cooling power of
78°
existing homes as well.
30°
BLINDS DON’T REALLY HELP People often use internal shading, such as blinds, to keep the heat out of their homes.
Ligh
While it’s certainly better than letting sunlight stream in unimpeded, it’s really not a good strategy if you look at the science. When sunlight shines through the glass in
[inside]
t th r ough
g las
s
[outside]
[outside]
windows, its wavelength lengthens. These
Short UV light rays
longer wavelengths cannot travel back out
[inside] Long infrared heat
through the glass, so the heat gets trapped inside. (This is how greenhouses maintain their warm environments.) When you put up blinds, you block light from getting into the room. However, the heat from the sun’s rays has already entered through the glass. Because heat always moves from hot to cold areas, the heated air trapped between the window glass and the blind moves into the cooler areas of the house. Blinds may help a bit, but it’s better to invest in exterior shading devices to stop the sun from ever entering the house rather than trying to control it once it’s there.
2. Let the House Breathe a Bit
design houses to work in partnership with their environment rather than to function with no regard for it? To understand best what ventilation can do for your home, you need to remember two simple principles: One is that heat always moves from hot areas to cold areas, and the other is that warm air rises. If you are designing a new house, spend some time on the site, learn where the breezes come from, and use that informa-
When mechanical systems are sized for
tion when locating the windows on your
a home, they’re often designed with the
house. Use casements that swing open to
mind-set that the house is never open to
help catch breezes. Having different units
the elements. I find this is rarely true; in
open in different directions allows you to
fact, most of my clients very much want to
take advantage of winds coming from mul-
connect their home’s indoor and outdoor
tiple directions.
spaces. Doesn’t it make more sense, then, to
Cool Design for a Comfor table Home
139
A studied approach. designing this secondfloor library as an open balcony permits warm air to rise unimpeded up and out the secondfloor windows. ceiling fans assist the natural airflow.
The simplest form of smart ventilation is cross ventilation. When you open a window
Chimney Effect
in your home, you can let in a slight breeze,
Hot air exits; cross ventilation accelerates air movement.
but when you then open a window on the opposite side of the room, the strength of that through-breeze increases significantly. If the entry window is small and the window through which the breeze exits is large, it increases in speed. A cool breeze in the evening when the sun is going down absorbs the heat in your house (heat moving from hot to cold); as the air heats up, it rises. So the best way to let hot air out of your house
140
Heating and Cooling
Air warms and rises.
Cooler air
is to have a large opening up high. The greater the distance between the intake and
Agriboard panel
the output, the better. This air movement is called the chimney effect (see the drawing on the facing page). I use it in my three-story home. When a cool breeze comes at the end of the day, I open the windows downstairs and the French doors on the third floor and wash out the entire house in minutes. The effect is heightened by an open plan, a small footprint, and a staircase in the middle that makes the whole house very much like a chimney. Vaulted ceilings and high windows in a clerestory or cupola also promote the chimney effect. The sloped ceiling encourages
in and out when you choose and to close up the house when you want. If you can, use more insulation than local
air to move to the top of the cupola, and
codes require, and add the sealing package
operable windows on both sides allow cross
that many insulators offer. Spray-foam in-
ventilation.
sulation provides a high R-value in a small
If you live in a dry climate, you can boost
amount of space and can double as an air
your home’s ventilation cooling with water
seal. That’s particularly important here in
cooling. Dry air moving over water absorbs
the Southeast, where moisture in the air can
moisture and subsequently drops in tem-
lead to mold, poor indoor-air quality, and
perature. (This is how evaporative coolers
even structural damage.
work.) Placing windows near a pond or an-
If you’re building a new house, look into
other water feature lets you capture the cool
building systems that offer insulation values
air as it comes off the water and into the
that are at least double what standard stick-
house. You get free air-conditioning along
built structures offer. In addition to precast
with the soothing bonus of a water view.
concrete panels and AAC (aerated autoclaved concrete) block, you might consider
3. Tighten Up and Insulate the House
agriboard panels. Made of compressed wheat
As I mentioned in section 2, passive cooling
R-value of 25.4 versus the R-13 or R-15 of a
involves being able to control the airflow and heat moving through a house. This
straw sandwiched between oriented strand board (OSB), these 8-in.-thick panels offer an standard 2×4 fiberglass-filled wall.
tighten up the house with good insulation,
4. Control Heat with Mass
caulking all penetrations and sealing around
With the correct orientation and south-
windows and doors. Weatherstripping ex-
facing windows, your house can have great
terior doors and installing double-paned,
light and heat in winter—but it also can
argon-filled windows with low-e coatings
have the potential for overheating if you
can help as well. Put a tight-fitting damper
don’t balance the amount of windows in the
in the chimney and a properly insulated
house with the amount of mass. Thermal
cover over any attic access. Making your
mass comes from materials that absorb heat,
home’s envelope tight enables you to let air
such as concrete, tile, brick and concrete
means stopping unwanted air infiltration by creating a tight building envelope. You can
Cool Design for a Comfor table Home
141
Floor mass. The floor is the easiest place to add thermal mass, which regulates temperatures all year long. This colored concrete floor is covered with a soy-based sealer and runs throughout the first level of the house. During the day, it absorbs excess heat from the south-facing windows, releasing it at night.
block, and water. However, water requires
once more, the cooled mass material starts
diligence to prevent algae and mold, and it
to absorb the day’s heat all over again.
is harder to incorporate into the structure of a house. The easiest mass to build into a
on the floor. A significant amount is needed:
house is some form of masonry.
In a typical passive-solar home, the concrete,
Generally, the more south-facing win-
installed on cementboard on a subfloor is
needs to balance the heat gain indoors and
not enough. Trombe walls are another design option.
windows, it strikes interior surfaces. Sun-
They are interior masonry walls behind
light can either radiate into the air, heating
south-facing windows with a narrow air-
the house, or be absorbed by the material
space between them. When the sun comes
it strikes. If it is absorbed, you get light in
in, the heat is trapped in the airspace and
the house but not heat. Because heat moves
then is absorbed by the wall. It acts as a heat
from hot to cold, the mass material will
sink for the house and can radiate the heat
continue to absorb heat as long as it remains
inside.
colder than the surrounding air.
Heating and Cooling
tile, or brick floor should be 4 in. thick. Tile
dows there are, the more mass a house keep it cool. When sun shines through the
142
The easiest way to add mass to a house is
If you’re planning a new house, you
The right amount of thermal mass draws
also can build mass into the walls. Precast
heat out of the air during the day, and radi-
concrete panels or AAC blocks introduce a
ates the heat to warm the home in the eve-
significant amount of mass. These walls can
ning when the air temperature drops, mak-
be finished in a variety of ways; stucco is
ing mechanical heating less necessary. In
the simplest and most low-maintenance op-
the morning, when the atmosphere heats up
tion, but you can attach siding if you prefer.
On the inside, concrete panels are typically painted, while the AAC can be finished with stucco or drywall. Finished this way, the interiors look like any other house, except for the added aesthetic of deep windowsills. Thermal mass has an added benefit: Not only does it absorb heat, but it’s also cool to the touch, which cools you. You can keep the air temperature of your home several degrees higher in the summer if you’re walking on a cool floor. One way heat is transferred is through conduction—the movement of heat from one object to another through direct contact. You touch the floor, and because you are warmer than the floor, the heat in you (the warmer object) moves to the floor (the cooler object). You feel cooler, no mechanical means required. Massing is the hardest strategy to add to an existing home. If the house was not designed to accommodate a 4-in.-thick masonry or concrete floor, it’s not easy to add one. If you are adding to the south side of your house, however, you can consider a slab floor, a masonry wall, or a masonry fireplace.
5. Choose Energy-Efficient Mechanical Help While I’m a firm advocate for passive cooling, I also believe there is a place for mechanical systems. Used in conjunction with passive-cooling techniques, the effectiveness of both can be enhanced, leading to lower energy use without any compromise in comfort. That said, if you are going to use both passive and mechanical systems, it’s important they work together. When hiring a heating and cooling contractor, choose someone who can size a mechanical system with your passive-cooling elements in mind and who will recommend energy-efficient equipment.
Start small. Strategically placed mechanical devices, such as the fan at the top of the hallway, can enhance passive design.
Cool Design for a Comfor table Home
143
Sources Seeking Solar Professionals When considering passive design, you should seek the services of a qualified pro familiar with the right strategies for your home and climate. Professionals accredited by the U.S. Green Building Council’s LEED (Leadership in Energy and Environmental Design) program are a good place to start. Make sure anyone you hire to size or install mechanical systems understands the effect your home’s passive elements will have on the system. The following resources can help in your search:
• U.S. Green Building Council: www.usgbc.org • American Solar Energy Society: www.ases.org • North Carolina Solar Center: www.ncsc.ncsu.edu • Energy Star program: www.energystar.gov • Southface Energy Institute: www.southface.org
Mechanical assist. This fan, at the top of the sloped ceiling, can also enhance passive design.
If your climate demands it, one mechani-
That brings us back to mechanical air-
cal component you might consider is a de-
conditioning. I like to view the AC as sup-
humidifier. When you rely on natural ven-
port for the passive systems in the house,
tilation to cool your house, you need to be
rather than the default switch we all reach
aware that letting in the breeze also means
for the moment the weather outside heats
letting in moisture. When the air leaves,
up. For those of us whose climate or
the moisture may remain. In these cases,
personal comfort level demands some air-
mechanical systems can help to dehumidify
conditioning, passive cooling can still
the air, preventing mold and damage to
extend the “shoulder seasons,” limiting AC
your home.
use to a few weeks a year. In the hot, moist
The best way to introduce mechanical
Southeast, occasional AC use is particularly
cooling to a passive house is to start small.
beneficial for dehumidification. Like the
Ceiling fans are a simple way to enhance
passive-cooling strategies you choose, the
natural ventilation. If you’ve installed
mechanical system you install should be
radiant-floor heating tubes in the floor slab,
geared to your home, your climate, and your
you can boost its cooling effect by pumping
comfort needs.
cool water through the pipes in summertime. Although this strategy must be carefully monitored to avoid condensation, it can have the added benefit of preheating your domestic hot water. 144
Heating and Cooling
Sophie Piesse is a LEED-accredited architect in North Carolina.
Central Air-Conditioning: Bigger Isn’t Better By Chris Green
S
itting in a green-and-white woven lawn
abound nationwide. According to a recent
chair, fanning away the sweat, my
study, 95% of new air-conditioning instal-
grandmother said, “It’s not the heat, it’s the
lations fail in regard to operating efficiency,
humidity.” With seven Virginia summers
with more than 70% of systems improperly
behind me, I suspected that the heat did
sized or installed.
have something to do with it, but I kept this thought to myself. It turns out that each of us had it partly
The top three reasons for poor airconditioner performance are improper sizing (1.5 to 2 times too large is common);
right. It was the combination of high heat
improper installation (incorrect refrigerant
and humidity that raised us to our exalted
levels and airflow); and poorly designed
level of discomfort on that oppressive
and installed duct systems. Because air-
summer day.
conditioning systems integrate refrigeration,
Seven years later, my parents finally built a house that included central air-
air distribution, and electronics, there are lots of opportunities for mistakes.
conditioning. Although it was better than
spots, and my basement bedroom always felt
Air Conditioners Move Heat Outside
cold and damp.
Heat naturally moves from a higher energy
being without, the air-conditioning system wasn’t ideal. The house had cold and hot
Unfortunately, these problems weren’t limited to my parents’ house nor to the 1970s. Problematic air-conditioning systems
level (warm) to a lower energy level (cool). You could say that heat, like water, flows
HEATING AND COOLING
4
Whether it’s new or a replacement,a properly sized and installed system affords greater savings and comfort.
downhill. Without help, heat that accu-
late refrigerant in a loop. By manipulating
mulates within a home will not leave on
pressure and temperature, the indoor unit
its own unless the heat sources (the sun,
absorbs heat by blowing warm indoor air
people, appliances, etc.) are removed. Help
over a cold coil. The heat is released to the
comes in the form of air-conditioning,
outdoor unit, which houses a compressor
which uses refrigeration combined with ven-
(which compresses refrigerant and itself
tilation essentially to push heat uphill, or
generates heat) and a condenser coil and fan
move it outside, where it’s even warmer.
(which dissipates the heat to the outside).
Residential air-conditioning systems are
146
Heating and Cooling
In addition to cooling, air conditioners
made up of an indoor and an outdoor unit
serve another important function: They
connected by a pair of pipes that circu-
dehumidify the air. In the same way that
How It Works Residential air conditioners are split systems—an indoor and an outdoor unit—that remove heat from the house and release it outdoors. A pair of pipes, which circulate refrigerant, form a loop and connect the units. Cold air is produced when compressed refrigerant is forced through a tiny valve or metering device (1) and expands into the evaporator coil (2), similar to the cold spray an aerosol can produces as the compressed liquid passes through the valve. This causes the refrigerant’s pressure and temperature to drop quickly, cooling the coil. As warm air passes over the evaporator, it is cooled and dehumidified. Moisture condenses on the evaporator’s fins and drains away. After absorbing heat from the home’s interior, the refrigerant is pumped to the outdoor unit, where it passes through the compressor (3) and is sent to the condenser (4) to lose some of its heat.
4
1 3
2
moisture condenses on the side of a cold
designed to run efficiently.” The first prob-
soda can sitting outside on a hot day, air
lem is that they dehumidify poorly. Oversize
conditioners wring moisture from warm,
units satisfy the temperature at the thermo-
humid air as it is forced across the indoor
stat so quickly that only a little moisture
unit’s cold evaporator coil. Once past the
has time to condense on the evaporator
evaporator, cool dehumidified air is deliv-
coil. This phenomenon is known as short
ered to the rest of the house—unless there’s
cycling, and it’s more of a problem in humid
a problem.
climates. If cycles are very short, moisture on the coil can evaporate back into the
Oversize Units Dehumidify Poorly and Waste Money
house before it drains away.
Approximately two-thirds of all residential
more of their time is spent running in the
air conditioners are too large. According to Bruce Harley, an HVAC consultant with Conservation Services Group in Westborough, Mass., these oversize units “will cool your house, but they’re not necessarily
Second, air-conditioning units are least efficient when they start up. It can take 15 minutes to reach operating efficiency, so oversize units run more short cycles, and least efficient part of the cycle. As a result, they use more energy, and costs to operate them run 20% to 30% higher than for properly sized systems. Finally, at an installed
Central Air-Conditioning: Bigger Isn’t Better
147
Reducing Your Cooling Needs
A
ir conditioners consume about two-thirds of electricity use during peak summer periods. Save money by making energy-efficient improvements before installing a new air-conditioning system. • A tight, well-insulated building reduces cooling needs by keeping warm, humid air outside. • Buy high-performance, low-e, argon-filled windows to reduce solar gain, which accounts for up to 70% of the cooling load on air-conditioning systems. • Wide overhangs, trees, or vegetation is helpful. East-west glass is more of a problem than south-facing glass in summer. • Use radiant barriers on the underside of uninsulated roof rafters if the HVAC equipment is in the attic; otherwise, just insulate the attic. In addition, insulate the ductwork. • Install smart thermostats that turn off the air-conditioning when it’s not needed and then bring the house to the right temperature before you arrive home.
cost of around $1,000 per ton, oversize sys-
as the insulation values of walls, ceilings,
tems cost more. Why pay for 5 tons if 21⁄ 2
and floors. Window types, locations, and
will do the job?
specifications as well as internal-heat gains (people, lighting, and appliances) also are
How Much Cooling Do You Need?
figured in.
Smaller systems use less energy and re-
footage of a house. In her book Air-
move more moisture because they run long enough to reach peak efficiency. So what’s the right size for an air-conditioning system? It depends. The standard method for calculating the proper size for a residential central airconditioning system is found in ACCA’s (Air Conditioning Contractors of America) Manual J—Residential Load Calculation by Hank Rutkowski, P. E. It’s a methodical approach to arrive at room-by-room cooling loads for sizing ducts and whole-house systems. The room-by-room totals are important because you can’t design a duct system properly without this calculation. Manual J takes into account and averages solar-heat gains, which don’t peak in all rooms at the same time. It also includes the house’s orientation to the sun and shading, which greatly affect the cooling load as well 148
Heating and Cooling
The right-size system is not a rule-ofthumb amount derived from the square Conditioning America (Johns Hopkins University Press, 1998), Gail Cooper writes that air-conditioning engineers 100 years ago called sizing by the rule-of-thumb method “futile and foolish.” According to the folks that I’ve talked to, that remains true today.
Contractors Sell Large Systems because They Fear Complaints In defense of the people selling and installing large air-conditioning systems, they do so for a reason. Profit plays a part, sure: If you install a bigger system, you make more money. More important, though, contractors fear complaints about their systems’ inability to maintain set temperatures in extremely hot conditions. Using a rule-of-
thumb measurement or some other method, the contractor sizes the system larger. If
You Just Want to Be Comfortable
3 tons is good, 4 is better, right? Besides, “Maybe Manual J sizing isn’t quite big enough,” a contractor might say, or “Here, it gets hotter than that.” A recent study, however, puts these fears to rest. Proctor Engineering Group (PEG), Electric Power Research Institute, Nevada Power, and Arizona Public Service tested a typical house with outdoor temperatures of up to 116°F (3°F above the mean extreme). The actual cooling required was less than Manual J predicted in all but three of the 1,316 hours that the house was monitored. It’s not necessary to oversize beyond Manual J, which has a built-in oversizing margin. On the first page of the introduction, Manual J states that “slightly undersized cooling equipment—by a margin of 10% or less—may actually provide more comfort at a lower cost.”
Most Air-Conditioning Systems Are Installed Improperly
M
ost of us don’t want to worry about our air conditioners. They aren’t high on our priority list. We expect air conditioners simply to make our homes comfortable, summer after summer. But what is comfortable? Feeling comfortable isn’t about temperature only. It’s about a favorable blend of temperature and humidity. And of course, what’s just right for one person might not be right for another, so comfortable becomes a range. That comfort zone is somewhere between 68°F and 78°F with relative humidities ranging from about 25% to 65%. To remain in the comfort zone as temperatures go up, relative humidity must go down (see the drawing below). Even though most of us can sense changes in temperature of 1°F to 2°F, we are less sensitive to humidity. Levels between 25% and 65% feel about right. According to ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), less than 25% relative humidity can lead to dry nose, throat, eyes, and skin. Greater than 70% can lead to mold, corrosion, and decay. High relative humidities in carpet and fabric can lead to dust-mite infestation and mildew (mildew is mold growing on fabric).
Winter
Another major reason for poorly performing
Summer
air-conditioning systems is faulty installation: incorrect refrigerant levels, low airflow, and poorly designed and installed duct systems. In one study of 55,000 air-conditioning systems by PEG, refrigerant levels were wrong 62% of the time; in another study, the figure was 68%. Condenser units arrive from the factory with the proper amount of refrigerant for a given length of piping—usually 15 ft. or 25 ft.—to connect the indoor and outdoor units. Refrigerant levels often are wrong because line length in the field can vary, and technicians frequently don’t make adjustments according to the manufacturer’s
90 80 Relative 70 humidity 60 %
50 40 30 65˚ 70˚ 75˚ 80˚ 82˚ Winter and summer comfort zones differ, but each is a favorable blend of temperature and humidity.
Tempera
ture
recommendations. What difference does it make if refrigerant levels are wrong? According to Armin Rudd of Building Science Corporation, if
Central Air-Conditioning: Bigger Isn’t Better
149
How Do You Find a Good Installer?
they are a little low, up to 20%, there’s some loss of cooling. More than that, and there’s an unacceptable loss of cooling along with
B
ecause 70% of all central air-conditioning systems are installed improperly (according to a California new-home construction study), you could be paying anywhere from 25% to 50% too much in air-conditioning bills. Choose your airconditioning installer carefully, or pay the difference in higher energy and maintenance costs. One measure of a technician’s expertise is whether he or she has completed a training program. All the major manufacturers offer training on installing their systems. In addition, several national certification programs are available through NATE (National Association of Training Excellence®; www.natex .org) and CheckMe! (through Proctor Engineering Group; www. proctoreng.com). CheckMe! is available in California, much of the Northeast (in some places under the Cool Smart name), and several other states. Technicians who complete their program perform diagnostic tests on each system and call in their results to a CheckMe! staff person to receive immediate feedback on the health of the system. Afterward, PEG sends a certificate of completion to the homeowner. Local electric utilities are another source for installercertification programs similar to NATE or CheckMe! Rebates or incentives might be available for high-efficiency equipment. In addition to asking about certified training, here are some other questions to ask installers: • Do they use Manual J for sizing air-conditioning systems? • Are they using proper design temperatures for your area? • Will they verify that the indoor unit’s evaporator coil and the outdoor unit’s condenser coil match and that the system has the proper amount of refrigerant? • Do they seal the ducts and test the system for leaks to a level of 10% or less? • Do they test airflow at the evaporator coil? • Can they provide references?
frosting of the evaporator coil and, eventually, complete loss of cooling. If refrigerant levels are too high, the story is similar: loss of cooling with possible damage to the compressor. The speed and the volume of air moving through air-conditioning systems were incorrect (usually too low) in about 72% of units tested in the PEG study. This was due partly to mismatched indoor and outdoor units, which occurs more often on retrofits than on new installations because only the exterior compressor/condenser unit typically is replaced. Also, airflow at the evaporator coil often is low because it usually isn’t tested, so no one actually knows what it is. Fan speeds at the evaporator coil should be around 400 cfm (cu. ft. per minute) per ton of cooling capacity. Slightly lower fan speeds improve dehumidification. In dry climates, fan speed should be increased. Tied to airflow and directly affecting it are duct design and installation. Ducts are the least expensive part of the system and frequently are given short shrift. A properly designed duct system begins with determining the cooling load for each room (not based on the square footage), which can vary greatly. Duct runs need to be as short as possible; they need to be insulated; and when possible, they should be installed within conditioned space. Ducts also should be sealed. Leaky ducts waste energy and in the right conditions might draw dust, spores, or combustion gas from a gas appliance back into the house. Adequate return air also is important to minimize air-pressure imbalances that can affect cooling. The placement of registers in the room and the quality of the grilles greatly affect the duct system’s ability to throw air across the room and to mix the air properly. Chris Green is a carpenter and cabinetmaker in New Milford, Conn.
150
Heating and Cooling
Low-Energy Lighting, High-Energy Design By Randall Whitehead
T
alk about energy-efficient lighting these
connector into a screw-in socket). We keep
days, and there are two technologies
expecting these new lighting technologies to
that are sure to dominate the discussion:
act (and cost) the same as the old ones. The
fluorescents (usually compact fluorescents)
problem is that they don’t.
and light-emitting diodes, or LEDs. As a
A prime example is the typical screw-in
lighting designer in California—where
compact fluorescent lamps (“lamp” is the
energy regulations are the strictest in the
industry term for “bulb”) offered at big-box
nation—I have a lot of these conversations.
stores. Technology-wise, they are the worst
And I can tell you that rather than get-
examples of what’s currently available. But
ting turned on by these newer, watt-saving
marketers wanted to provide a CFL at rough-
technologies, most people are immediately
ly the same price as an incandescent lamp.
turned off.
What you end up with is a cheaply made
Why? Because most people have already
bulb that can buzz, produce an off-color
had a lifetime of bad experiences with flick-
light, and is not dimmable. So what hap-
ering, buzzing fluorescents and know little
pens? CFLs in particular, and energy-
about LEDs, except that they’ve become
efficient lighting in general, gets a bum rap.
ubiquitous as strings of the latest must-have
The fact is that many manufacturers (see
holiday lights.
“Bulb Sources,” p. 154) are making efficient
It’s not that these new light sources aren’t
lamps that perform well. Yes, they do cost
as good—or better—than the incandescent
more up front, but in the long run, they
bulbs they’re designed to replace. But here is
offer greater energy savings and let you be
a classic example of trying to fit a square peg
earth friendly and design savvy at the
in a round hole (or in lighting terms, a pin
same time.
lighting and appliances
5
Evocative and efficient. In the author’s living room, a collection of photographs is uplit with LED festoon lamps from Phantom™ Lighting. Ambient light is provided by recessed fixtures from Lucifer® Lighting that are outfitted with LED MR16s from Focus Lighting®.
It’s my job to practice what I preach.
layering that designers have long relied on
My house is filled to the brim with energy-
to produce attractive, well-lit spaces. Light
efficient light sources. In fact, the only two
layering incorporates four specific types of
incandescent lamps I own are in my refrig-
lighting to create a well-lit environment:
erator and oven. Other than that, it is all
task, accent, decorative, and most impor-
high-efficacy all the time. Is it warm and in-
tant, ambient light. The rule here is that
viting? Absolutely. You don’t have to change
more than one light source is needed to
every lamp in your house, as I did. Start
illuminate a room properly. The challenge
slowly. Maybe put A-lamp shaped CCFLs
when working with new, energy-efficient
(cold-cathode compact fluorescent lights)
types of lighting is that you have to go be-
in your exterior lanterns and CFLs in the
yond light layering and understand how
basement and the attic. Try using daylight-
these new sources create light in order to use
colored CFLs in your closets for better color
them correctly.
matching for articles of clothing. Every little
For example, CFLs, CCFLs, and ESLs (see
bit helps—but it helps the most when each
“Low-Energy Lighting: The Latest
of these different light sources is used to its
Bulb Technologies” on the facing page) are
best advantage.
omnidirectional sources of light. This means they throw light out evenly in all directions,
Layering: Shining New Light on the Old Rules
which is what a standard household “A”
While new ways of producing light offer lots
accent lights.
of design possibilities, it still makes sense to stick with the tried-and-true basics of light 152
Lighting and Appliances
lamp (like our old incandescent) does. That makes all of these types good sources of ambient and decorative lighting, and occasionally task lighting; but they are ineffective as LEDs, by contrast, are unidirectional, meaning that their light is projected out in
one direction. As a result, they can provide a very good source of accent lighting and task lighting, and occasionally ambient light if used correctly or if designed in a luminaire (fixture) that compensates for their unidirectional tendencies. In addition to the differences in how they project light, these new light sources differ in the color (temperature) of light they produce. Other characteristics, such as resistance to temperature change, ability to dim, and available wattages, also can influence your decision on what type of bulb to use where. Once you know the properties of these earth-friendly light sources, you can begin to include them more confidently to produce each of the layers of light that combine to produce a well-lit room.
Low-Energy Lighting: The Latest Bulb Technologies compact FluorEscEnt l amps An aversion to fluorescents is understandable because they have been so awful for so long. They didn’t dim easily; they buzzed and gave off weird colors. And sadly, the push to offer CFLs at a price point close to that of a standard incandescent household bulb has given fluorescents a bad name all over again. The color of these cheap CFLs is poor, they burn out prematurely, and they aren’t dimmable. There are much better products on the market. Be prepared to pay more, but they will be worth it. Topof-the-line screw-in CFLs by manufacturers like MaxLite™ and Earthtronics® (see “Bulb Sources,” on p. 154) offer an energyefficient, dimmable (down to 30%) light source that can be controlled by a standard incandescent dimmer. A new category of CFL is the GU-24, characterized by a proprietary lamp and socket assembly that cannot be replaced with a standard screw-in incandescent lamp
Esl: the next bright idea in low-Energy lighting
y
ou may not have heard of ESL technology, but it’s the newest kid on the lighting block. It looks like an incandescent lamp, and it dims like an incandescent lamp—but it’s not. ESL (electron stimulated luminescence) lighting technology uses accelerated electrons to stimulate phosphors to create light. But unlike fluorescents, ESLs contain no mercury, turn on instantly, and promise full-range dimming. They also don’t require the heavy heat dissipation designs of LEDs. The color of the light is warm— very close to that of incandescent. Developed by Seattle-based VU1® Corporation (www.VU1 .com), they began shipping R30 reflector lamps, commonly used in recessed fixtures, in late 2010. Other lamp styles are expected to follow.
(although MaxLite makes a screw-in adapter that allows a typical lamp to accept a GU24 socket). The GU-24 lamps meet California’s Title 24, which requires that 50% of the wattage in kitchens must come from hardwired high-efficacy sources and 100% of the wattage in the bath must come from high-efficacy sources, unless controlled by a switched motion sensor. For savvy people everywhere, lighting manufacturers are now offering decorative fixtures in modern and traditional styles that have hardwired fluorescent sources.
cFl
Many use the new GU-24 socket and lamp technology, which is no bigger than a standard household bulb and socket assembly. They
Low-Energy Lighting, High-Energy Design
153
Bulb sources 1000BULBS.COM ® : specialty lamps online; www.1000bulbs.com
can be installed where there is an existing
cents. Companies like Cree Lighting® and
incandescent fixture and can be dimmed
Progress Lighting® offer both screw-in and
with the existing incandescent dimmer. No
hardwired LED kits as retrofits for existing
special wiring or dimmer is needed.
housings, as well as IC-rated, airtight housings for new construction.
Earthtronics: dimmable cFls and ccFls; www.earthbulb.com
colD cathoDE FluorEscEnt l amps
Philips Color Kinetics: led MR16 lamps and color-changing leds; www.colorkinetics.com
household bulbs, globe lamps, or flame-tip
Cree Lighting: Recessed led lights, including retrofit trims; www.creelighting.com
8w CCFL produces 40w worth of illumina-
Edge Lighting: led strip lights; www.edgelighting.com LiteTronics ® :
cold cathode fluorescent lamps (ccFls); www.litetronics.com
CCFLs are a newer generation of fluorescent lamps. They can look just like regular lamps. They cost more than an incandescent, about $12 each, but save an average of $33 in energy costs over their lifetime. An tion and lasts 25,000 hours, compared to an
High-Energy Design: Creating a Well-Lit Room with Four Types of Lighting
incandescent with an average rated lamp life
tasK lighting: both lEDs anD FluorEscEnts arE up to thE job
of 750 hours. What makes them better than
Task lighting is the lighting by which you do
regular CFLS is their wide variety of color
work, including undercabinet lighting in a
temperatures and that they can dim down
kitchen, closet lighting, and reading lamps.
MaxLite: gU-24 lamps and sockets, and screw-in cFls; www.maxlite.com
ccFl
a full 90% (CFLs can’t
The optimum task light provides shadow-
dim that much). Their
free light and is located between your head
swirls are thinner, and
and the worksurface.
they’re more widely
Depending on the type of fixtures
available than CFLs in
being used, both fluorescents and LEDs can
Phantom Lighting: led shelf & display lights; www.phantom lighting.com
low wattages. They are
provide effective task lighting. Fluorescent
still a bit hard to find;
puck lights, such as those by Tresco Interna-
they must be special-
tional (www.trescointernational.com), offer
Progress Lighting (Everlume™ Series): Recessed led lights, including retrofit trims; www.progresslighting .com
ordered through light-
shadow-free illumination along worksurfaces
ing specialty stores or
such as kitchen counters. Because much of
bought online.
today’s architecture is open plan (where one
Tresco International ® : Fluorescent , led, and xenon puck lights; www.trescointerna tional.com
room flows into the other), choose a light
light-Emitting DioDEs
with a color temperature of 2,700 K so that
In use since the 1960s, LEDs were used as
the color is complementary to light sources
colored indicator lights. About three years
in other rooms.
ago, manufacturers came up with an LED
For task lighting in closets and laundry
source with the same color qualities of in-
rooms, consider using 5,000 K lamps from
candescent light and daylight. These new
LEDs or CFLs for excellent color matching.
LEDs use considerably less electricity than
Although some people dislike the lag time
standard incandescent sources and last
associated with CFLs, I like to use them in
much longer—30,000 to 50,000 hours, while
closets. In fact, I don’t need a sudden punch
emitting no ultraviolet radiation. Even bet-
of light in the morning. I also appreciate
ter, they contain no mercury, as do fluores-
the color rendering—very important when matching clothes—that’s possible with a combination of CFLs and LEDs. Those energy-eating xenon and halogen festoon lamps used in undercabinet task lights and shelf lights come in LED versions; those offered by companies such as Phan-
led
154
Lighting and Appliances
tom Lighting (www.phantomlighting.com)
Closet coordinated. A strip of 5,000 K LED festoon lights above the clothing shows their true colors under daylight conditions (top) compared to incandescent lighting (bottom).
are dimmable. Other options for undercabi-
and family. This unfortunate result is often
net task lights include LED puck lights from
referred to as the “museum effect.”
Lucifer Lighting (www.luciferlighting.com)
LEDs work well as accent lighting for
and LED strip lights by Edge Lighting (www.
several reasons: They provide directional
edgelighting.com).
light, they produce no UV (ultraviolet) rays
One caution when using LEDs as task
that can harm fine artwork or textiles, and,
lights: because they are point sources of il-
unlike incandescents, the color temperature
lumination, they tend to create multiple
doesn’t alter when they are dimmed. Fluo-
shadows, which can be distracting. Hiding
rescent light sources are usually too broad in
LED sources behind a diffusion material
their beam spreads to be effective as accent
eliminates this problem.
lights. An exception to this rule would be the illumination of a wall mural or a large
Accent lighting: The spotlight goes to LEDs
hanging tapestry. In these cases, I recom-
Accent lighting is used to highlight specific
to reduce possible degradation of the art.
objects, adding depth and dimension to an environment. Recessed adjustable fixtures,
mend adding a UV-filter to the light fixture
track lights, portable uplights, and directional
Decorative lighting: CCFLs show off just enough
landscape lights all fall into this category.
Decorative lighting also could be called ar-
Accent lighting can be very dramatic, but
chitectural bling. Its purpose is simple: to
when overused can make the objects you
look pretty and to add visual sparkle to a
own appear more important than friends
space. Chandeliers and candlestick-type wall
The right accent. Here, this niche is illuminated with a single LED MR16 housed inside a square-trimmed recessed low-voltage fixture from Lucifer Lighting. The absence of UV light will help to preserve the integrity of the photograph.
Low-Energy Lighting, High-Energy Design
155
Just enough light. Because they can be obtained in flametip styles and lower wattages than typical CFLs, CCFLs are often more suitable (and less overpowering) in decorative fixtures with multiple bulbs, such as this breakfastroom chandelier.
sconces fall into this category. Decorative
provides overall illumination, but it also
lighting should not be relied on to provide
softens the shadows on people’s faces, help-
primary light for a room. If it’s too bright,
ing them to look more relaxed and youth-
it can be overpowering. These fixtures were
ful. I refer to it as architectural Botox. The
originally designed around incandescent
best ambient light comes from illumination
light sources, particularly those of a low-
that is bounced off the ceiling. Opaque wall
enough wattage so as not to be overpower-
sconces, torchieres, pendant-hung indirect
ing. The best replacement, then, among
fixtures, and cove lighting can be used to
the newer light sources would be CCFLs,
create ambient light (see “Green—and
because they can have a color temperature
Unseen,” below). Translucent fixtures can
similar to that of a dimmed incandescent
sometimes serve double-duty as both
lamp. I particularly like the MicroBrite™
ambient and decorative light. Both LEDs
A19 by LiteTronics, which has a very warm
and fluorescents can provide excellent
color temperature of 2,250 K and, being a
ambient light.
CCFL, dims down a full 90%. LEDs would lighting because they do not provide an
Green—and Unseen
even, overall glow.
When I show my clients a typical CFL—
have to be the worst choice for decorative
the type shaped like swirly soft ice cream—
156
Ambient lighting: Fluorescents have a slight edge
they immediately hate it. It doesn’t matter
Ambient lighting is the gentle light that
if it operates quietly, or if it’s dimmable.
fills the volume of an interior with a warm
They just have a visceral, negative reac-
glow. Because it is indirect light, it not only
tion because they can see that the source
Lighting and Appliances
if the light it produces has a beautiful color,
of light is fluorescent. I’ve learned to apply a technique I call stealth lighting. Stealth lighting simply means hiding the bulb behind a diffusion material such as a shade, an architectural detail, or a lens. If they can’t see that it’s a fluorescent source, most people assume the light is incandescent and find it perfectly acceptable.
Layers of efficiency. All four basic layers of light combine in this open-plan living room/ kitchen. The Flotation pendant fixtures by Ingo Maurer® are fitted with dimmable CFLs, providing both decorative and ambient light. Reading lamps flanking the sofa provide task light, and the square aperture recessed lights add ambient light.
When selecting a decorative fixture—for example, a pendant light—find a bowlshaped one that hides the bulbs; in the case of a drum-shaped fixture, look for one with a lensed (translucent) bottom. The CCFLs that are now on the market are available in shapes that are closer to traditional ”A” lamps and flame-tipped bulbs that are easily accepted as incandescent without any disguise. Another good way to create energyefficient ambient light for a space is to install the light source within an architectural
High on efficacy. Ambient light for this kitchen comes from linear fluorescent lighting mounted on top of the kitchen cabinets. The lighting over the counters comes from warmcolored fluorescent puck lights, made by Tresco International. Low-Energy Lighting, High-Energy Design
157
Sources for Energy-Efficient Decorative Fixtures The Basic Source ® : Faux and real alabaster pendants with fluorescent lamp options; www.thebasicsource.com Birch & Willow: Light fixtures made of natural materials with fluorescent lamp options; www.birchandwillow.com Boyd Lighting: High-fashion fixtures with fluorescent lamp options; www.boydlighting.com Dave Meeker Art : Pendants, wall sconces, and portable fixtures made of plastic straws, using CFLs; www.davemeekerart.com Elica ® : Pendants with integrated fans; www.elica.com Hans Duus Blacksmith: Traditional and transitional fixtures
with LED and GU-24 options; www.hansduusblacksmith.com JH Lighting: Traditional and transitional alabaster fixtures with hardwired CFL options; www.jhlighting.com
Stealth lighting. Energy-efficient light sources can be unobtrusive: The Lightspann pendant fixtures in this living room conceal dimmable CFLs. Art and tabletops are lit by Juno® track fixtures using LED MR16s, and LED strips by Edge Lighting mounted on top of the trusses provide ambient light.
Juno Lighting: Recessed, track, undercabinet, and decorative lighting; www.junolightinggroup.com
detail that runs the perimeter of the room
Kalco ® : Decorative lighting, much of which is available in hardwired fluorescent versions using GU-24 technology; www.kalco.com
linear fluorescent source can do an excel-
Lightspann: Sculptural fixtures with GU-24 lamp options; www.lightspann.com
to make sure that the actual light source is
Schmitt Design: Bamboo pendants with GU-24 lamp options; www.schmittdesign.com
paint on the ceiling is a flat or matte finish.
or on top of cabinetry that does not go all the way to the ceiling. Here, a dimmable lent job, as well as some of the newer LED strip lights now available. In these cases, the light is bounced off the ceiling, so you want completely hidden from view and that the A gloss, semigloss, or eggshell finish reflects an image of the light source onto the ceiling and ruins the effect. Randall Whitehead is a San Francisco–based lighting designer.
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Lighting and Appliances
LIGHTING AND APPLIANCES
5
The Bright Future of Lighting BY SEAN GROOM
Small, powerful, and efficient. Now that they produce white light appropriate for residential settings, LEDs grouped together in a bulb pack enough punch that this 8w LED from Nexxus™ can replace a 75w PAR30 incandescent bulb.
A
lthough still a relatively small slice of the incandescent-dominated light-
The Energy Independence and Security Act (EISA) of
ing market, energy-efficient compact fluo-
2007 soon will limit the
rescents (CFLs) and light-emitting diodes
number of watts a bulb can
(LEDs) have gained traction over the past
consume for a given number
few years, thanks to green-building pro-
of lumens, a measure of light output. The
grams and some progressive local energy
legislation takes effect Jan. 1, 2012, when the
codes. They’re about to get a real boost.
luminary equivalent of today’s 100w incan-
Continuous task lighting. The unique tubes and connectors of Feelux®’s Slimline allow end-to-end installation, eliminating shadows and dark spots between fixtures in undercabinet and cove lighting.
sion. Today’s CFLs, however, produce light in the 2,700 K range, mimicking the warm, amber-hued light of incandescent bulbs (see the sidebar on the facing page). Also, the old magnetic ballasts have been replaced with quiet electronic ballasts that don’t flicker. CFLs are dramatically more efficient than incandescent lightbulbs, using between 50% and 80% less energy, and they last for about 10,000 hours, nearly 10 times longer than incandescents. They also cost dramatically more. However, replacing one 50¢, 75w incandescent bulb with a $3.50, 19w CFL saves 563kwh of electricity over the life of the bulb. That comes to about $75 in savings, Replacement bulbs for every application. Often part of the fixture, fluorescent lights need a ballast to operate. These replacement bulbs from Philips, however, have onboard electronic ballasts, which means they can be screwed into existing fixtures for more efficient ambient and decorative lighting. CFLs with pin bases are for fluorescent-only fixtures required by some energy codes.
descent bulb will be allowed to consume
depending on the cost of electricity where
only 72w. (Lower-wattage bulbs also will
you live.
be affected.) In other words, incandescent lightbulbs
On the downside, a typical CFL contains somewhere between 4 mg and 5 mg of mer-
need to become about 28% more efficient to
cury. Critics of CFLs highlight the health
survive. Some industry insiders think they
and environmental hazards of mercury, and
will, but CFLs and LEDs already meet the
special precautions should be taken if the
new requirements. Consequently, the most
bulbs break in your house. Proponents argue
likely scenario is that incandescent bulbs
that the mercury in a CFL is far less than the
will be replaced either by CFLs or LEDs, de-
amount of mercury emissions that would be
pending on the application.
released from a coal-fired power plant if you were using an incandescent bulb. Regardless,
Compact Fluorescents Come of Age
when a CFL burns out, it must be recycled so
CFLs were introduced in the early 1990s,
cluding Ikea® and The Home Depot®, offer
but they weren’t ready for prime time. Early CFLs produced harsh blue light, hummed, and flickered, making a poor first impres160
Lighting and Appliances
that the mercury doesn’t end up polluting the environment. Some retailers of CFLs, inCFL recycling. To find other recycling locations, visit www.epa.gov.
The Color of Good Light
N
Light-Emitting Diodes Are the Future LEDs are a Silicon Valley technology, manufactured in a clean room, just like a computer chip. Electrical current runs through the 1-sq.-mm chip, exciting the electrons and creating light. A small bulblike cover focuses the light. LEDs can’t actually produce white light; white light must be created either by combining colors or by using a phosphor coating inside the bulb. The lighting industry is betting heavily on forging ahead with significant advances in white-light LED technology in the next few years. Many of today’s LEDs, however, already perform well when used in the appropriate location. Manufacturers describe LEDs as cooloperating lamps. While it’s true that the lit end of an LED is cool to the touch, the semiconductors do produce heat. And just as
10,000 K North light (blue sky)
9,000 K
8,000 K
7,000 K Overcast daylight
Degrees kelvin
Dedicated ambient light. Retrofitting an old recessed can with a screw-base CFL could cause premature heat-induced bulb failure. CFL-dedicated recessed cans properly dissipate heat and maximize light output. The can at top, from Halo®, is remarkably similar to a standard incandescent fixture with the addition of a ballast attached to the junction box. The fixture below, from Lightolier®, orients the bulb horizontally and needs just 31⁄ 2 in. of clearance.
o matter what type of fixture or bulb you’re using, you need to understand light temperature to light your home effectively. There is a spectrum of white light from “warm,” which has a yellowgold hue, to “cool,” which has a bluish cast. The hue of the light is described by correlated color temperature (CCT) and is measured in degrees kelvin, as shown on the scale on the right. Lower numbers are associated with warmer light and higher temperatures with cooler light. For example, an incandescent bulb commonly used in homes has a temperature of about 2,700 K, while the daylight fluorescents commonly used in office buildings are about 4,100 K. Along with most finishes in our homes, people look best under warmer light—2,700 K to 3,000 K. Although cooler light looks harsh on wood, it can be complementary to white and stainless-steel finishes, which are common in homes with modern designs. A second measure of light quality is color-rendering index (CRI). When you compare the same color under different light sources, you might notice a color shift. CRI is an attempt to quantify this shift by describing— on a scale of 0 to 100—how well a light source renders color. Good CFLs have a CRI above 80. If you’re in the market for LED lighting, you’ll have to see the light for yourself to make an educated purchase. LED standards for CCT or CRI have been voluntary, and some manufacturers’ ratings might be called generous.
6,000 K
5,000 K Noon daylight Direct sun Electronic flashbulbs
4,000 K
3,000 K
Household lightbulbs Early sunrise Tungsten light Candlelight
2,000 K
1,000 K
computer chips require cooling to perform The Bright Future of Lighting
161
Out-of-sight task light. Under cabinets is a natural place to use LEDs because their small size keeps them out of sight and because they’re cool to the touch. Also, unlike fluorescents, they don’t interfere with radio or TV reception. Lights are available in a range of styles. Select only the amount of light you need so that glare off the counter isn’t an issue. The fixture to the left from Kichler® is one example.
Replacement bulbs. Most LED replacement bulbs are directional for accent or task lights, such as the MR16 replacement from Nexxus, above left. A new generation of LEDs is trying to offer multidirectional ambient light with replacements for fluorescent tubes (from Ilumisys®, above center) and for the common table lamp (from Philips®, above right).
properly, LEDs need thermal management. The heat sink, usually a number of large aluminum fins located near the base of the lamp, is a critical component of an LED. LEDs are already more efficient than incandescent bulbs, producing approximately 60 to 70 lumens per watt, and manufacturers expect efficiency to surpass that of CFLs soon. Their 50,000-hour average life span translates into 34 years when used four hours a day. There are other advantages to LEDs’ solid-state engineering as well: They are immune to vibration, and their performance improves in cold temperatures, making them ideal for outdoor applications. Cost is currently the biggest drawback to LEDs. A screw-in LED replacement for a recessed light costs about $120, but remember that LEDs are the lighting equivalent of a computer chip: Just as Intel® founder Gordon Moore predicted that chip capacity would double every two years (Moore’s Law), Haitz’s Law (named for scientist Roland Haitz) states that every decade, LED prices will fall by a factor of 10 while performance will increase by a factor of 20. Excellent accent lighting. Small disks (from Kichler, above left) and night-lights (from Kichler, above right) provide the low light levels needed for highlighting artwork or providing safe nighttime navigation. Easily concealed, they work in enclosed cabinets without heat buildup and use very little energy to illuminate.
162
Lighting and Appliances
Still, a word of caution is appropriate. There are some well-engineered LED bulbs and fixtures on the market, but with so many manufacturers jumping on the band-
wagon, there are plenty of LEDs with harsh light and poor switching and dimming
Efficacy at a Glance
response. It’s a good idea to evaluate these products carefully before purchasing.
Match the Light to the Job Both CFLs and LEDs are available with screw-in bases as replacement bulbs for existing fixtures, but if you are building a new home or remodeling, you might consider
O
ne measure of lighting efficiency is efficacy. Efficacy is expressed as lumens per watt (lm/w)—the amount of light produced for each unit of electricity consumed. Incandescent lights have efficacies between 10 and 20 lm/w, and fluorescents range from 60 to 100 lm/w. LED products tested recently by the U.S. Department of Energy’s Solid-State Lighting program were in the 70 to 80 lm/w range. However, LEDs are expected to surpass fluorescents soon and exceed 150 lm/w by 2015. The chart below shows representative examples.
fixtures dedicated to one technology or the other. Dedicated fixtures can lengthen
COMPARING RECESSED FIXTURES
the lifespan of the bulb and maximize its strengths. Both CFLs and LEDs play a role in
Incandescent
CFL
LED
Watts
65
15
12
Lumens
52
675
730
Efficacy (lm/w)
10
45
60
providing ambient, accent, task, and decorative lighting, the four layers that create a well-lit room. But CFLs and LEDs aren’t necessarily interchangeable. That’s largely because CFLs are a multidirectional light source and LEDs are a point source. Because they are multidirectional and produce large amounts of diffuse light, CFLs work well for ambient, task, and decorative lighting (photos pp. 160–161). They can be used nearly everywhere that incandescent bulbs are used, particularly in table lamps and in shielded sconces, where the fabric or glass adds color to the light. In the bathroom, when they’re used behind opaque glass, CFLs do a great job of lighting your face. In kitchens, in laundry rooms, and in offices, CFLs produce bright-enough ambient light to illuminate worksurfaces. CFLs are not appropriate everywhere, however. Locations where lights are switched on and off quickly—say an entry hall or a coat closet—are not ideal because CFLs need time to attain their full brightness and because short-cycle switching reduces the bulbs’ lifespan. Also, if you’re using a CFL bulb in an outdoor fixture, make sure that it’s labeled for outside use, which means that the ballast will work in cold temperatures.
Task and Accent Lighting Require Focused Light LEDs produce a focused beam of light. Although their relatively small output means they can’t throw light as far as some incandescents, there are plenty of circumstances where they work well as task lights. And they’re ideal for accent lights because they don’t produce UV-light that damages paintings and fabrics. Because LEDs are small and easily produced as pucks or strip lighting, they are ideal for undercabinet illumination or as accent lights hidden in coves or inside cabinets, where small size and low heat output are important. Glare can be a concern with bright LED fixtures, especially recessed lights. San Francisco Bay Area lighting designer Eric
The Bright Future of Lighting
163
Kind of canlike. Although the fixtures look quite common, like the Halo model above, the light module for recessed LED fixtures bears little resemblance to a bulb. With a screw-in adapter like the one shown attached to the Halo module at right, LEDs can be retrofit to existing recessed fixtures.
Johnson recommends using a diffuser with
Under the first approach, variations in the
recessed cans or, at the very least, recessing
amount of phosphor coating on each diode
the bulb as deep into the fixture as possible.
affect the overall color of the light. When
Lightolier®’s
Calculite™ is a lensed fixture
you have multiple downlights in a room,
that uses a diffuser to create white light.
this can result in variations in the light from
Instead of coating the LED bulbs with phos-
the different fixtures. It’s easier to apply an
phor, the phosphor is applied to the diffuser.
even, consistent phosphor coating to a glass diffuser, improving the consistency and the color of the light. Placing the reflector above the phosphor layer results in more light
Sources
output than other methods and less glare,
The companies listed here had products that impressed us at LightFair®, the annual lighting-industry trade show. Visit www.americanlightingassoc.com for a comprehensive list of lighting manufacturers. American Fluorescent : www.americanfluorescent .com Cooper Lighting (Halo): www.cooperlighting.com Cree: www.cree.com Feelux: www.feelux.com Ilumisys: www.ilumisys.com Journée Lighting ® : www.journeelighting.com
164
Lighting and Appliances
Kichler: www.kichler.com Lightolier: www.lightolier.com MaxLite: www.maxlite.com Nexxus: www.nexxuslighting.com OSRAM ® Sylvania ® : www.sylvania.com Philips: www.philips.com
according to the manufacturer. A unique feature of LEDs is that a single fixture with different types of diodes can create multiple temperatures and colors of light, opening new design possibilities for accent lighting. One last thing: Both CFLs and LEDs can be tricky to dim. The ballasts and drivers, respectively, must be compatible with the dimmers, and the light may cut out before dimming down all the way. This information is usually indicated on the product. Sean Groom is a contributing editor to Fine Homebuilding. He lives outside Hartford, Conn.
lIGhTInG and applIancES
5
The EnergySmart Kitchen by alEX wIlSon
10% 26%
W
64%
hen it comes to electricity consump-
for nearly two-thirds of kitchen energy
tion, the kitchen is the hungriest
use, with ranges, ovens, and cooktops ac-
room in the house. Kitchen appliances—
counting for a little over one-quarter, and
including refrigerators, freezers, ranges, and
dishwashers the rest. Add in the heating,
dishwashers—account for nearly 27% of
air-conditioning, hot water, and lighting
household electricity use. Collectively, that’s
used in a kitchen, and this room is clearly
more than 300 billion kilowatt hours (kwh)
the energy hog of most houses. Putting your
per year in the United States, or roughly the
kitchen on an energy diet might be one of
electricity output of 90 average-size coal-
the best things you can do to save money
fired power plants.
and resources. Like most diets, it all comes
Not all appliances are equally voracious, however. Refrigerators and freezers account
down to making informed choices.
Where does the energy go? kitchen appliances on average account for more than a quarter of household electricity use, and the appliances we use to keep food cold— refrigerators and stand-alone freezers— together are the biggest consumers. ovens, coffeemakers, and cooktops, as a group, are the secondhungriest appliances in the kitchen, followed by dishwashers.
Two Tools to Measure Energy Efficiency
T
he blue Energy Star label and the yellow EnergyGuide sticker help consumers identify energy-efficient appliances. Energy Star labeling denotes compliance with guidelines set by the U.S. Environmental Protection Agency and the U.S. Department of Energy. Appliances rated by the program include dishwashers, refrigerators, and freezers (but not cooking appliances). Although Energy Star compliance indicates an energy-efficient appliance, some models exceed the requirements more than others (see www.energystar.gov). Unlike the voluntary Energy Star program, the EnergyGuide label is required by the Federal Trade Commission on all fridges, freezers, and dishwashers (but not on cooking appliances). The label shows the model’s capacity, its estimated annual energy consumption and operating costs, and a scale that compares its efficiency to that of similar models. The EnergyGuide label helps in comparison shopping but does not indicate Energy Star compliance.
Refrigerators Are the Top Energy Guzzlers In a typical American home, the refrigerator accounts for about 15% of total electricity use. Assuming heat and hot water are not electric, that makes the refrigerator a home’s single largest electricity consumer. This is the case even though refrigerators have improved dramatically since the mid-1970s; today’s models use about a third as much power as those from 30 years ago.
Refrigerators: Style and Use Determine Efficiency What to avoid • Through-the-door ice and water dispensers. Both the lost insulation and the additional cooling coils in a throughthe-door ice and water dispenser increase electricity consumption.
Frugal features. The most popular features with consumers—such as automatic defrosting and through-thedoor ice and water dispensers—are not always the most energy efficient. Still, Maytag®’s Ice20® refrigerator meets Energy Star requirements and is equipped with two potentially energy-saving features: an alarm that alerts homeowners to a refrigerator door left ajar and a vacation mode that saves energy by limiting automatic defrosting when the fridge isn’t opened for several days.
166
Lighting and Appliances
•A utomatic ice makers. Ice makers consume energy, though exactly how much is
Innovations to Watch For
difficult to determine.
What to look for
Vacuum-panel insulation
efficient refrigerators and freezers
Thermos bottles keep coffee hot because most of the air molecules in the double wall have been removed, keeping conductive heat transfer very low. The same idea has been incorporated into flat vacuum panels. Back in the mid-1990s, Whirlpool® produced high-efficiency refrigerators that used inchthick vacuum panels made by Owens-Corning, which had center-of-panel insulating values of R-75. The technology hasn’t completely caught on, but it’s currently used by KitchenAid®, a Whirlpool brand. Silicaaerogel insulation is another material that could find its way into refrigerators; it insulates better than the polyurethane foam used in most models.
have manual defrost, although they can
Variable-speed compressors
• The Energy Star label. The U.S. Environmental Protection Agency confers its Energy Star label on models that are at least 20% more energy efficient than the federal minimum. Shopping for this label is an easy way to be sure the refrigerator you choose is not an energy waster. • Freezers on top or bottom. Side-by-side refrigerators use more energy. • Manual defrost cycles. The most energy-
be hard to find, particularly among highend models. • Door alarms. Some manufacturers offer an alarm that will sound if the fridge door is left open—helping to save energy and to prevent food spoilage.
Maintaining high performance • Place fridges away from heat sources— especially a range or oven, but also a dishwasher. Radiant heat from these appliances
Compressors account for 83% of a refrigerator’s energy use, so an efficient compressor means an efficient refrigerator. Variable-speed compressors save energy by operating at low speed during low-usage periods (such as overnight) and then running faster during periods of high usage. Still mostly limited to European brands and professional-style built-ins, variable-speed compressors are used in some GE® Profile™ and Monogram® products, as well as Whirlpool’s high-end built-in lines. Other manufacturers may soon follow suit.
warms the surface of the fridge, requiring more energy to keep the inside cool. If the refrigerator must be adjacent to a heat source, provide space for air circulation. • Clean the coils, at least annually. Dust and dirt buildup on refrigerator/freezer coils reduces the heat-exchange efficiency and makes the compressor work harder. Most refrigerators now have coils that can be accessed from the front, eliminating the need to pull the unit away from the wall. • Turn off the condensation-control feature. Essentially, these are heating elements under the protective shell that consume energy in two ways: by using electricity to warm the outer shell and by increasing the difference in temperature across the unit’s insulation. Models with
this feature usually have a switch to turn it off; do so, unless condensation becomes a problem. • Keep the freezer full. Frozen food serves as a thermal stabilizer that reduces the amount of on-off cycling. If you don’t have a lot of frozen food, freeze containers of water (use plastic, and allow for expansion as the water freezes) to take up the extra space. When you need ice for a cooler, you can use these frozen containers. • Don’t keep an extra fridge in the garage. When you buy a new refrigerator, avoid the costly mistake of keeping the old one as a backup.
The Energy-Smar t Kitchen
167
Cooking Options Pit Efficiency against Cost More efficient cooking saves energy and money directly, of course, but by keeping waste heat out of the kitchen, it also saves on air-conditioning. Although this impact might not be huge in a typical home, it can make a difference. As a rule, electric cooking
and on during the cooking or self-cleaning process. Those 375w (or even as much as 500w in some ovens) are a significant amount of electricity. If low electricity use is a priority in your home, consider a model without a glow bar, such as ranges made by the Peerless-Premier Appliance Co. (www. premierrange.com), which operate with a pilot or a spark ignition.
fueled appliances a more economical choice.
Cooktops & Ovens: Electric Wins over Gas
Gas cooktops also afford better heat control
Cooktop efficiency is difficult to measure,
than their electric counterparts.
and relatively little attention has been paid
appliances are more efficient than gas-fueled ones. But the relative price of natural gas versus electricity often makes natural-gas-
Because their functions are so different,
to it, primarily because stovetop cooking ac-
it’s important to consider cooktops and ov-
counts for a small percentage of household
ens separately, even though they might be
energy use—about 5%, according to the
combined in a stand-alone kitchen range.
American Council for an Energy Efficient Economy. My research shows that electric
Gas Ovens Draw Electricity, Too
cooktops are the most efficient, and gas the
With ovens, rapid heat-up and cooldown
of efficiency based on the energy factor,
aren’t as important as with cooktops, mak-
which is the ratio of the amount of energy
ing electric ovens more competitive with
conveyed to an item being heated to the de-
gas, even for serious cooks. In fact, it is not
vice’s overall energy consumption. Expressed
uncommon for high-end ranges to have a
as a decimal, it reflects the proportion of
gas cooktop and an electric oven. Again,
energy used that actually contributes to the
electric models are more efficient: Electric
cooking of food.
ovens are 1.8 to 3.5 times as efficient as gas ovens, according to U.S. Department of Energy (DOE) data. Cost efficiency, however, largely depends on which type of fuel costs the least in your area. Most gas ovens also use a lot of electricity while operating. In nearly all gas ovens today, when the gas burner is operating, an electric glow-bar igniter (sometimes called a “gas oven igniter”) is on, drawing about 375w. (Interestingly, at a recent International Builders’ Show, not one kitchen-appliance salesperson who was asked seemed aware of this fact.) Found in all self-cleaning models, the glow bar ignites the gas when the oven is turned on and reignites it as it cycles off
168
Lighting and Appliances
worst. The section below ranks the most common cooktop technologies in order
Cooktop T ypes Induction Although induction technology initially failed to take off when introduced a decade or so ago, it’s back, with more highend induction cooktops entering the market. On an induction cooktop, electrical energy is transferred directly to ferrous-metal cookware through magnetic induction. Efficiency is the highest of any cooktop (about 84%) because the cookware is heated directly. It’s also a safer way to cook: The cooking surface does not heat up, enabling photos like the one at top left on facing page, where water boils in a cutaway pan while ice cubes rest intact on the “burner’s” surface. Induction
Induction Energy Factor: 0.84
electric coil Energy Factor: 0.737
gas, no pilot Energy Factor: 0.399 radiant Energy Factor: 0.742
gas, pilot Energy Factor: 0.156
cooktops also heat up and cool down quick-
Electric coil Available on low-cost ranges
ly, providing precise controllability. Down-
and cooktops, these old-fashioned open-coil
sides include high cost and the fact that on-
elements are slow to heat up and difficult to
ly certain cookware can be used. Cast-iron,
clean, but fairly efficient at transferring elec-
enameled cast iron, and some stainless-steel
tric energy to the pot.
cookware work. Test yours to make sure a magnet sticks to it, or look for a label.
Gas (natural or propane) Cooks prefer gas burners for speed and controllability, but
Radiant ceramic The most common mid-
indoor-air-quality experts often recommend
to high-end electric cooktop today, it has rel-
against gas for health reasons. Although gas
atively fast-heating radiant elements under
cooktops rate worst in terms of energy ef-
ceramic glass, providing a sleek, easy-to-clean
ficiency, they are usually more cost-efficient
stovetop surface. Flat-bottom cookware
because the price of natural gas is typically a
is needed for good surface contact; older-
lot lower than electricity. Gas cooktops use
style cast-iron pans are not recommended
only about 40% of the energy produced, and
because burrs on the metal can scratch the
if there’s a continuously burning pilot light,
glass surface. Radiant-ceramic cooktops heat
the overall efficiency is far lower (about
faster than electric coils and are nearly equal
16%). In some areas, propane is nearly as
in energy efficiency.
expensive as electricity per unit of delivered
The Energy-Smar t Kitchen
169
energy, making electric cooktops a more eco-
ovens and oven Fans
nomical option. The efficiency of natural gas and propane is essentially the same.
S
elf-cleaning ovens typically have more insulation than standard ovens, so if you have a choice, go for a selfcleaning model. The extra insulation keeps the outer surface of the range from becoming too hot during the self-cleaning cycle, but it also helps the oven to operate more efficiently.
Microwave Ovens Are Tops in Efficiency First introduced as a practical kitchen appliance in 1965, microwave ovens have
oven fans
revolutionized cooking and offer substantial
Convection ovens have a fan in the back that circulates air to maintain more-even temperatures. As a result, either the cooking time or the temperature can be reduced. The energy savings from reduced gas or electricity use for cooking easily outweigh the fan’s electricity use.
energy savings over standard ovens (They are 5 times as energy efficient as a standard electric oven). They work by producing non-ionizing microwave radiation (a certain frequency of radio waves) with a magnetron and directing that radiation at the food. The microwave radiation is absorbed by water, fats, and sugars, producing heat. Because the microwaves penetrate the food, heating is more rapid and requires less energy than in a conventional oven. Microwave ovens are about 5 times as energy efficient as standard electric ovens and more than 10 times as energy efficient as gas ovens. Increasingly, manufacturers are combining cooking functions with microwave ovens to produce a new generation of “rapid-cook” appliances. These models combine microwaves with electric grilling elements so that food can be browned as well as cooked. Quartz elements are often used to create radiant heat, though General Electric’s Advantium® microwave oven (www.geappliances .com) uses a halogen-lamp element. Convection is another feature offered by the Advantium and some others, such as TurboChef®’s Speedcook Oven (www.turbochef.com). In the future, most ovens likely will include
ovEn EFFiciEncy By typE
170
oven type
Energy Factor
Microwave
0.557
Electric (self-cleaning)
0.138
Electric (standard)
0.122
Gas (self-cleaning)
0.054
Gas (standard)
0.030
Lighting and Appliances
multiple heating options to speed up cooking and to serve a wider range of functions, from defrosting to reheating to grilling.
odors but should not be relied on to remove
Tips to Cut Consumption Lid on or off? If you use a convection oven, keep the lid off a casserole dish. Otherwise, it will cook no more quickly than in a standard oven. On a cooktop, closing the lid on a pot will retain heat and reduce energy use.
Consider a Crock-Pot Slow-cooking, plug-in crock pots offer an energy-efficient way to cook soups, stews, and other dishes.
combustion gases. A significant energy-saving feature to look for in a range-hood exhaust fan is a variable-speed motor. This allows the fan to operate at a lower airflow rate when full ventilation capacity is not needed, thus saving energy and reducing noise.
Dishwashers Are Shaping Up Dishwashers have changed quite a bit in recent years. They use a lot less water, which translates into lower energy use for water heating. In 1978, water use by dishwashers ranged from 11 gal. to 15 gal. for a normal dishwashing cycle. By 2000, that usage had
Exhaust Fans Are Important to Health
dropped to 6 gal. to 10 gal. As water use has gone down, total energy use has also dropped, while the proportion of energy use for processes other than water
Exhaust fans add to energy consumption,
heating has risen. In 1978, 83% of the total
but their importance with regard to kitchen
energy use for dishwasher operation was for
air quality—and the health of your home’s
heating water; 10% was for motor opera-
occupants—cannot be ignored. Chemical
tions, and 7% for drying. By 1994, energy
impurities in natural gas, along with incom-
use for water heating had dropped to 56%,
plete combustion, can result in dangerous
according to a 2003 Virginia Tech report.
levels of carbon monoxide (CO), causing
However, that does not mean most dish-
headaches and fatigue at low levels and, at
washers are as energy efficient as they could
high concentrations, death. Because of this
be. Nearly all dishwashers today have boost-
concern, gas ranges should be installed with
er heaters that increase the temperature of
quality, outdoor-venting range-hood fans,
incoming water to about 140°F to improve
which should be operated when the cooktop
wash performance. An integral electric ele-
or oven is on.
ment provides this heat, and it can use a lot
Exhaust fans are most efficient when
of electricity. Recent independent testing
placed above the cooktop or range. Down-
shows that booster heaters operate through-
draft fans, which are installed at the back
out the dishwashing cycle, resulting in
or in the center of a range, rely on signifi-
total electricity use per cycle of 2.0 to
cant airflow (and power consumption) to
3.5 kwh. Used an average of 215 times per
ventilate cooking fumes effectively. Because
year (the frequency DOE assumes), a dish-
fumes are more easily channeled into a fan
washer could easily consume more elec-
installed in a range hood, fan performance
tricity annually than a refrigerator. More
is better.
research is needed to determine the signifi-
If you can’t vent an exhaust fan outdoors,
cance of this electricity use.
avoid the use of gas cooking appliances. Recirculating range-hood fans can remove
The Energy-Smar t Kitchen
171
Dishwashers vary considerably in their energy use, much more so than refrigerators. For comparison, dishwashers are rated by the federal government according to their energy factor (EF), a measurement based on the energy usage for an average number of cycles (a completely different formula than the one used to rate cooking appliances). The higher the EF, the more efficient the dishwasher: The current federal standard mandates a minimum EF of 0.46; Energy Star dishwashers must meet a minimum EF of 0.65. The most-efficient dishwashers have an EF that approaches or slightly exceeds 1.0. Although the EF is used to compute the annual energy consumption and cost estimates found on the EnergyGuide label on many appliances, the EF itself might not appear there.
Dishwashers: Less Hot Water Equals Less Energy Use Drawerful of savings. Compact dishwasher drawers can be highly efficient (both of these models from New Zealand manufacturer Fisher & Paykel® are Energy Star compliant). An added bonus is that the integrated models, like the one pictured above, blend seamlessly into kitchen cabinetry.
What to look for • The Energy Star label. Energy Starqualified dishwashers are at least 41% more energy efficient than the federal minimum. Keep in mind that some models exceed the standard significantly more than others; check the EnergyGuide label or the list of qualifying dishwashers at www.energystar.gov for high-performing machines. • Soil sensing. With this technology, “fuzzy logic” is used to determine how dirty the dishes are. Water use and wash cycle are adjusted accordingly, saving significant water and energy. • No-heat drying. Most dishwashers have an electric heating element and fan for drying dishes. Make sure the one you buy has a no-heat drying option, which can save a significant amount of energy.
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Lighting and Appliances
Top performers. The Bosch® Evolution line includes dishwashers that exceed the minimum federal energy-efficiency standard by 147%—far more than any American-made dishwasher—using approximately the same amount of energy as a dishwasher half its size.
Easy button. The “EcoAction®” button offered on some Bosch dishwashers allows homeowners to reduce energy usage by up to 25%. Activating the feature lowers the wash temperature and extends the cycle by a few minutes.
A new way to clean dishes. Tshe LG® Steam Dishwasher™ uses only 2.8 gal. to 3.2 gal. of water in an average load.
Usage Tips • Insulate hot-water pipes from the water
Innovations to Watch For
heater so that water stays hot all the way to the dishwasher and doesn’t cool off as much between the different wash and rinse cycles. • Wash full loads only, even if it means waiting a day or two. • Avoid high-temperature cycles. Many dishwashers have a setting for more intensive cleaning in which the temperature is boosted, which can significantly increase electricity use per cycle. To conserve energy, don’t use this setting. Alex Wilson is founder and executive editor of Environmental Building News and president of BuildingGreen Inc. in Brattleboro, Vt. (wwwbuildinggreen.com). His latest book is Your Green Home (New Society Publishers, 2006).
Steam-cycle dishwashers LG has introduced a steam-cycle dishwasher that the company claims cleans dishes better. The washing cycle uses steam at over 200°F, apparently saving energy in the process because it uses a lot less water. You can choose different wash intensities for the bottom and top racks or a halfload option that cleans the top or bottom rack only.
Drawer dishwashers The New Zealand company Fisher & Paykel and KitchenAid both
offer drawer-type dishwashers. They can save energy and water by allowing you to use one smaller drawer rather than a partially loaded full-size dishwasher, or by allowing two drawers to be operated at different cycles.
Condensation drying While most dishwashers vent moist air into the kitchen as dishes are drying, Bosch models use condensation-drying technology, which the company claims improves hygiene and saves energy.
The Energy-Smar t Kitchen
173
LIGHTING and appliances
5
Solar Hot Water By Scott Gibson
T
here’s nothing like a looming energy
Florida brought the solar hot-water business
crisis to bring history full circle. More
to its knees.
than a century has passed since Clarence
Unobtrusive, efficient, and energy-smart. Heating water with the sun can be almost as simple as installing a solar collector on the roof. Resembling skylights, these collectors can provide hot water for baths, laundry, and even heat.
Does the story sound familiar? It should.
Kemp, a Baltimore heating-equipment deal-
A spike in energy prices and short-lived gov-
er, came up with the first commercial solar
ernment incentives created a solar hot-water
water heater. His patented Climax Solar
boomlet in the 1970s and 1980s. The inter-
Water Heater, which sold for $25, was a hit.
est withered when energy prices dropped
More-efficient designs soon came along,
and government subsidies dried up, stick-
and by 1941, half the houses in Florida had
ing homeowners with systems that didn’t
solar hot-water systems. Roof-mounted solar
always work and couldn’t be serviced due
collectors were common in California, too.
to the lack of qualified technicians. Rising
But natural-gas discoveries in the West and
energy prices are once again making solar
a utility blitzkrieg to sell more electricity in
attractive. But this time around, the industry
is offering more-dependable, better-designed hot-water systems that give homeowners in all parts of the country a reliable way to cut
Passive Systems Are an Affordable Option in Warm Climates
energy bills. Heating water with the sun can be pretty simple. In the right climate, a 55-gal. drum
Hot water to storage tank
ICS (batch) collector
painted black and perched on the roof provides plenty of hot water. Collectors like that, called batch heaters, are producing hot water all over the world. But technology has a lot more to offer these days, making solar hot water feasible for any region of the country and for just about any application, from swimming pools and hot tubs to domestic hot water and even space heating.
There Are Many Ways to Heat Water, but Keeping It Hot Is Another Story Although solar hot-water systems vary widely in design and complexity, they share some basics. The sun heats water, or another liquid capable of transferring heat, in a collector. Specialized materials called selective coatings are made to absorb available solar
In their simplest form, these systems consist of a batch collector (also known as integrated collector storage, or ICS) that’s pressurized by the household-water supply and exposed to the sun. When a hot-water tap is opened, water is forced from the batch collector to a conventional water heater or directly into the distribution system. Relatively easy to install, these systems are suitable only for warmweather areas. Solar Direct (www.solardirect.com) sells a passive-system kit for about $1,400.
radiation. They include black chrome, black nickel, and aluminum oxide combined with nickel or titanium nitride oxide.
Cold water in
Once water is hot, it’s either moved to a storage tank or piped directly to where it’s needed. That much seems simple, but the trick is making sure the water doesn’t cool down too much or, worse, freeze. To cover the wide range of temperatures and solar potential that hot-water systems can
Hot water to fixtures
encounter, manufacturers offer a variety of equipment and plumbing options. In general, systems are either active or passive, meaning they operate with or
Hot-water storage tank/water heater
without electric pumps. They also can be direct or indirect (sometimes called open loop or closed loop), which means the collectors heat the water that’s used in the house or, alternatively, heat a nonfreezing transfer medium that in turn heats potable
Solar Hot Water
175
water in a heat exchanger. In virtually all
have no trouble delivering that kind of
cases, solar-heated water is routed through
volume, but there aren’t any safe generaliza-
a conventional water heater, where it gets a
tions about whether it will be enough to
temperature boost (if necessary) before being
satisfy household demands.
distributed to its point of use.
“The thing with hot water is that there are wide variations in demand,” says Brad
How Much Hot Water Do You Need?
Collins, executive director of the American
Most Americans use about 20 gal. of hot
substantially less demand than the exact
water a day, a standard industry benchmark. Most hot-water tanks are sized for a single day’s consumption, so an average family of four, for example, might end up with an 80-gal. tank. Solar hot-water systems should
Solar Energy Society. “A 3,000-sq.-ft. house occupied by two elderly people will have same house next door that has five people, including two teenage girls. Their demand is tenfold what it is in the other house.” Other variables include the time of day when demand for hot water is high-
Passive Thermosiphons Rely on Convection Heated water to storage tank Tank
Cold return from tank
Hot water to fixtures
Cold water in
Hot-water storage tank/water heater
176
Lighting and Appliances
More-advanced passive systems employ a method of heat exchange called thermosiphoning. Water heated in the collector rises into the rooftop tank, displacing cold water that is returned to the bottom of the collector for heating. When a hot-water tap is turned on, water flows from the collector’s tank to the conventional water heater or into water-distribution lines. Solahart® (www.solahart.com) offers closed-loop models that provide freeze protection in colder climates. An online search found one dealer’s prices at $3,000 to $4,000 for models suitable for households of three to five people; another dealer quoted $5,000 to $7,000.
Collector
They work on the ground, too. As long as the solar exposure is good, it’s often easier and less expensive to install large collectors on the ground.
est, whether use comes all at once (morn-
systems. In Europe, says Tim Merrigan of
ing showers, for example) or is distributed
the National Renewable Energy Laboratory
throughout the day, the number of appli-
in Boulder, Colo., package systems that do
ances in the house and when they are used,
both are relatively common. But due to
and the amount of solar potential the house
heavy winter-heating loads and reduced
has. “It’s a different environment for each
solar potential, homeowners in this country
and every house,” says Collins. “It’s very
shouldn’t expect to get much more than
much occupant-driven.”
one-third of their winter heat from solar
If there’s such a thing as an average, the
sources with today’s technology.
Arizona Solar Center estimates that a solar
Elia Kleiman, the president of Synepex
hot-water system should be able to deliver
Energy in Cambridge, Mass., says the pro-
100% of hot water in the summer and about
portion of winter heat from solar depends
40% on a year-round basis. Performance var-
on the type of heating system, the amount
ies by region. A household of four people
of insulation installed, and the tightness
would need 40 sq. ft. of collectors for an
of the house. A best-case scenario in New
80-gal. tank in Arizona, 55 sq. ft. in South
England, land of snowy winters and cold,
Carolina, and 106 sq. ft. in Vermont.
dreary springs, is that a solar system meets
How this translates into savings on gas or
40% to 70% of the heating load. That’s in a
electric bills is also a wild card. Most solar
well-sealed house with a radiant-floor heat-
hot-water systems are used to heat water
ing system.
before it goes into a conventional water
Radiant-floor heating is especially well
heater, not as an outright replacement for
suited to solar hot-water systems because
a water heater fueled by gas or electricity.
it requires lower water temperatures, 120°F
Careful consumers who are flexible about
versus the 180°F that would be pumped
when they use hot water will see more solar
through a typical baseboard hydronic sys-
benefit than a family that wants a lot of hot
tem. Solar hot water also can be used for
water all at once. Under the right circum-
newer forced-air systems that use a technol-
stances, virtually all of a household’s hot-
ogy called “hydro air.” These boilers heat
water needs can be met by a solar system.
water forced through a heat-transfer coil,
But that’s no guarantee.
where it warms outgoing air.
“It’s like buying a
Toyota®
Prius®,”
says
For a hypothetical house of roughly
Collins, likening an investment in solar
2,500 sq. ft.—well insulated and well
hot water to owning one of Toyota’s hybrid
sealed—Kleiman says Synepex would prob-
cars. “You change the way you drive because
ably recommend eight evacuated-tube col-
it’s rewarding. You see how your involve-
lectors covering roughly 400 sq. ft. of roof.
ment can impact your miles per gallon. In
That would provide 100% of domestic hot
the same way, your involvement can im-
water in addition to what the system sup-
pact how much energy you’re going to be
plied to the space-heating side.
charged for, whether it’s thermal or electrical
Systems like that aren’t cheap. Although
energy. People become energy literate and
it’s difficult to offer meaningful numbers
smart energy consumers.”
without knowing specifics, Kleiman says that a solar-radiant floor system could eas-
Using Solar for Space Heating
ily cost $16,000 and possibly as much as
Solar collectors are commonly used for do-
for only domestic hot water. If the collectors
mestic hot water, but they also can supplement both forced-air and hydronic heating
$24,000 before tax credits and rebates. That’s many times more than a system designed were tied to a baseboard hot-water system rather than a radiant floor, a homeowner
Solar Hot Water
177
How Much Will My System Cost?
c
ost is a key consideration when weighing the merits of renewable energy, not only because the systems tend to be expensive, but also because they force us to think about energy in an entirely different way. A conventional water heater doesn’t cost much, but it’s expensive to operate over its lifetime. A solar hot-water system is much more expensive up front but costs less to use. Thinking in generalities isn’t helpful when it comes to deciding whether solar hot water is a reasonable investment. For specifics, I went to www.findsolar .com, a website run under the auspices of the Department of Energy, the American Solar Energy Society, and the Solar Electric Power Association. It’s an excellent place to get started on a hot-water system and provides a variety of other useful links. A worksheet let me plug in a lot of specifics: my state, county, electric utility, and the number of people living in the house. In just a few seconds, the site came up with the size of the system I’d need, length of payback, annual utility savings, and even return on investment. 1. In southern Maine, I’d need one collector of about 32 sq. ft. to produce the 35 gal. of hot water my wife and I would use in a day. Having the system installed would cost about $3,500, but after a state rebate and the federal tax credit, the net cost would be less than half that. Moreover, my property
value would increase by as much as $3,690, my annual utility savings would be from $224 to $335, and I would remove 21 tons of greenhouse gases from the air. That’s the equivalent of 42,000 auto miles. Years to break even? Between three and four, not including the system’s impact on property-value appreciation. If I wanted estimates, a link would take me to a list of local installers, complete with contact information, services offered, and a brief summary of their experience. 2. In Tucson, Ariz., where utility rates are lower but the sun shines brighter, a similarly sized system would produce between $252 and $378 in annual utility savings. 3. In Pensacola, Fla., lower state incentives and utility rates drive the savings down to a range between $74 and $110. 4. In Dayton, Ohio, the savings are about the same as in Pensacola (about $85 per year). If electricity rates increase more in the future than now forecast, solar hot water will become a viable option for more people. Until then, when it comes to saving money with solar hot water, it seems that if you have high utility rates, you’d be smart to get a system on your roof. If not, the decision depends on your commitment to a cleaner environment.
1 4
3
2
kwh/m²/day kilowatt hours per square meter per day 4-4.5
178
Lighting and Appliances
4.5-5
5-5.5
5.5-6
6-6.5
6.5
Map indicates an annual average of daily solar-radiation potential for a south-facing flat collector array, mounted at an angle equal to its latitude. Data courtesy of National Renewable Energy Laboratory.
Active Systems Reduce Heat Loss Photovoltaic panel powers pump; grid current can also be used. Hot water to tank Flat-plate collector Hot water to fixtures
Cold water in
In active systems, electric pumps speed circulation to reduce heat loss. As illustrated here, water is run through flat-plate collectors (essentially heat collectors plumbed with a network of copper pipe) to the water heater. In areas subject to occasional freezing, an optional valve drains water into a secondary storage tank when its temperature approaches 32°F. The Alternative Energy Store® (http://home.alten ergystore.com) sells an open-loop kit consisting of two large flat-plate collectors, hardware, and pump for about $3,600. Shipping and installation are not included.
Hot-water storage tank/water heater
DC pump
Cooler water settles at bottom of tank and circulates to collector.
might expect to see solar take care of only
tal project in Canada where solar collectors
20% to 40% of the heating load.
are used to heat the ground when solar
A big drawback of trying to heat a house
potential is abundant in summer. In winter,
with solar hot water is that demand is high-
geothermal heat pumps can be used to ex-
est when the heat potential of the system
tract the stored heat. This seasonal storage of
is lowest. On an overcast day in northern
heat is one idea that could make 100% solar
New England, the sun is long gone by late
heat possible in the future—even in Calgary,
afternoon, and the call for heat goes up ac-
Alberta.
cordingly. The answer is to store hot water generated during the day in storage tanks so that it can be used for heat when the sun goes down or when the days are cloudy. Tanks can be very large, 2,000 gal. or more, although Kleiman says newer systems can use much smaller tanks that hold as little as 200 gal. Researchers are also looking down the road at promising new possibilities. Merrigan, for example, describes one experimen-
Rebates and Tax Breaks Could Be the Keys to the Future What takes the sting out of the high cost of buying into renewable-energy systems is a combination of federal tax credits and state and utility rebates. The federal credit, pegged at 30% of system cost, is open to
Solar Hot Water
179
Indirect Systems Are Most Efficient and Most Expensive In these active systems, a pump circulates glycol in a closed loop. After running through high-efficiency evacuated-tube collectors (or flat-plate collectors), the hot glycol returns to the storage tank, where a heat exchanger warms potable hot water. Essentially freezeproof, these glycol-charged systems are able to perform in any season. ReVision Energy® in Portland, Maine, put the price of an installed system adequate for a local family of four at about $10,000. Photovoltaic panel powers pump.
Temperature sensor
Heated glycol to heat exchanger
Hot water to tap
Evacuatedtube collectors
Cold water in Cooled glycol to collectors
Hot-water storage tank/water heater
Controller Heat exchanger
DC pump Temperature sensor
Expansion tank
everyone. State and utility rebates, however,
be enough to make people think about it,
vary. Where they are generous, such as in
but to not want to make that investment.
California or Hawaii, you can expect robust
If you have incentives that can bring
growth for the solar industry.
down that first cost, you see good market
Originally due to lapse in 2008, the federal tax credit has been extended for eight
penetration.” Still, credits and incentives are available
years. However, the on-and-off nature of
now, and they make a much bigger differ-
government support is a “travesty,” says
ence proportionally for hot water than for
Collins, and a chronic problem for the solar
photovoltaic systems. “You displace roughly
industry. “You can’t do this with stops and
2kw of energy with your water system, so it’s
starts,” he adds. “It’s been the history of
like putting a 2kw PV system on your roof,”
incentives for renewables for the past
says Collins. “But it’s hot water. A 2kw sys-
25 years.”
tem of PV might be $20,000, but a 2kw solar
Merrigan says that as many as 35% of all
hot-water system might be $6000. I’ve often
houses in Hawaii have solar water-heating
said that solar hot water is the most misun-
systems, in part because of generous rebates.
derstood bargain out there.”
“I think it’s key,” he says. “It’s just like for photovoltaics. PV is growing where there are incentives. The first cost of the system can
180
Lighting and Appliances
Scott Gibson, a contributing editor to Fine Homebuilding, lives in East Waterboro, Maine.
Collector Installation at a Glance
S
olar hot-water systems involve a fair amount of labor-intensive planning and plumbing, but a typical collector installation is fairly straightforward. On this membrane-covered shed roof, (1) the first step was to erect the aluminum frames that hold the panels. The frames are adjusted to a fixed angle that maximizes the collector’s solar gain and are bolted to blocking that has been integrated into the roof. (2) The panels, which weigh about 100 lb. each, are carried up and clipped onto each pair of frames. (3) Simple compression fittings connect the panels to plumbing. (4) The installers added two more panels and finished in about half a day. They spent another two days setting up the system.
Resources for Solar Information Alternative Energy Store: http://home. altenergystore.com; Solar information and products American Solar Energy Society: www.ases.org; Links, background information on solar energy Database of State Incentives for Renewables and Efficiency (DSIRE™): www.dsireusa.org; Database of energy incentives listed by state and type Find Solar: www.findsolar.com; Worksheets for estimating costs of solar hotwater systems
1
2
Florida Solar Energy Center ® : www.fsec.ucf.edu; Comprehensive site on all things solar, including efficiency ratings of collectors and systems by manufacturer Interstate Renewable Energy Council: www.irecusa.org; News, resources related to renewable energy National Renewable Energy Laboratory: www.nrel.gov; Lots of background information on renewable energy Solar Direct: www.solardirect.com; Solar information and resources
3
4
Solar Rating and Certification Corp.: www.solar-rating.org; Ratings for solar collectors and systems by manufacturer
Solar Hot Water
181
LIGHTING and appliances
5
Energy-Saving Thermostats By Sean Groom
I
nstead of turning down the thermostat
on cooling costs with a setting of 78°F to
on the way to bed and again on the way
85°F when you’re out or sleeping.
out the door, you can cut home-heating
mable thermostats. Basic models ($30 and
Check for Compatibility
up) store different settings for weekdays and
A programmable thermostat has to be com-
costs and count on a reliable, comfortable temperature with one of today’s program-
weekends. More advanced models ($90 and up) store a different program for each day of the week.
Minimize Operating Time to Save Money Whether a thermostat is manual or programmable, your savings result from the setback,
patible with your HVAC system. Be especially careful when choosing one for use with heat pumps or radiant floors. A temperature setback in heating mode can cause a heat pump to operate inefficiently. And because high-mass radiant floors are slow to lose and gain heat, temperature setbacks have to be timed differently. Finally, look for an Energy Star rating,
or the reduction in temperature from the
which ensures the thermostat is capable of
typical occupied setting. Studies by the U.S.
four daily temperature settings and is pre-
Department of Energy have found that the
programmed for efficient operation.
energy required to raise a home’s temperature to its normal level approximately equals the energy saved as the temperature falls to the lower setting. For each degree of setback over an eight-hour period, you’ll reduce energy consumption by 1%; the longer the setback, the more energy savings you enjoy. During the heating season, utility companies recommend a 68°F setting in the morning and evening and 55°F overnight and when you’re not home. You can economize
Installing a Programmable Thermostat Replacing a standard thermostat with a programmable one is easy on most HVAC systems, but there are a few things you need to pay attention to that usually aren’t included in the instructions. Hydronic (boiler) sys-
Choosing a Thermostat
HSIP15_illoA
Simple and inexpensive
M
T
W
T
F
S
S
HSIP15_illoAWeekday and weekend modes Hunter®’s most basic model has four heating or cooling periods each It follows S schedule M Tday.W T Fthe same S andschedule weekend modes for all weekdays, but you can set aWeekday different for the weekend. HSIP15_illoB Designed for simple installation, the device is battery-powered for W T F S S M T broad system compatibility. HSIP15_illoA HSIP15_illoB Weekday and two weekend modes
Smart and versatile White-Rodgers®’s
M TT W S W F ST S F M T Weekday and weekend modes Weekday and two weekend modes
S
midlevel HSIP15_illoC thermostat allows separate schedules for Saturday and Sunday, but uses the same program for weekdays. M Energy Star-rated S S T W T F thermostats HSIP15_illoB HSIP15_illoC Daily program modes such as this one take the guesswork out of recovering from a temperW T F S S M T ature setback, automatically reaching temperature by the S S M T the W target T F Weekday and two weekend modes Daily program modes start of the programmed period. This model adjusts its call for heat by five minutes for each degree of setback. (For example, the heat turns on at 6:05 if you program a 5°F change for 6:30.) HSIP15_illoC
easy, flexible programming
M
T
S W T F Daily program modes
Hunter Fan company Set & Save 44110, $35 (www.hunterfan.com)
White-rodgers IF80-0471, $60 (www.white-rodgers.com)
S
The flexibility of a high-end model like Honeywell®’s Vision Touch Screen allows you to enter a different schedule for each day. The touch screen relies on a menu-driven program similar to an ATM. A feature called “adaptive intelligent recovery system” tracks heating and cooling periods over time to “learn” how long it takes to bring your house to the programmed temperature, minimizing the system’s run time. The “auto changeover” setting Honeywell of thermostats in this price range switches between Vision Touch Screen rTH8500d, $109 heating and cooling modes automatically. (www.yourhome.honeywell.com)
tems are wired differently; a professional
transformer in the unit and the new ther-
can advise you on the best approach for
mostat. Remote thermostats for electric
your setup.
baseboards are typically line voltage (either 120v or 240v). In that case, be sure the
FOR A RETROFIT
thermostat you’re installing is made for
• First, cut power to the HVAC unit. That’s
line voltage, and be sure the power is off to
usually done by shutting off one or more circuit breakers: one if the unit is a heat pump, two if it’s an air conditioner and furnace. The breaker for a heat pump or AC compressor is a two-pole breaker, usually two breakers with a handle tie. Most thermostats operate at low voltage (24v), which comes from the unit, and you want the power off to protect both the
protect yourself. • Remove the old thermostat body from its base. It will either be a press-fit unit or be held together with screws. The leads from the thermostat cable usually are attached to terminal screws on the base. Each screw has a letter next to it; often, they’re molded into the plastic base and are not easy to see. If standard thermostat Energy-Saving Thermostats
183
Don’t Toss Your Old Thermostat
about 3⁄ 8 in. For a screw terminal, I usually strip about 11⁄ 2 in. off each wire and cut off the excess after I’ve tightened the screw.
o
ld mercury-switch thermostats contain enough mercury to poison a 60-acre lake. They should be recycled so that they don’t end up in a landfill, where the silvery element could leach into the water table. Mercury Manufacturers have established switch the Thermostat Recycling Corporation (TRC) for suppliers to collect old thermostats from contractors for recycling. (Visit www.thermostat-recycle.org for a list of participating wholesalers.) If a TRC participant won’t accept thermostats from homeowners, contact your local municipality’s hazardousmaterial recycling program.
• Run the cable through the hole in the new base, and fix the base to the wall with a suitable anchor. Insert each wire into the terminal clamp, or wrap each wire around its terminal clockwise so that tightening the screw closes the loop. Make sure there’s no insulation caught under the clamp or screw. If the cable is so short that I can’t make the new connections or if I want to relocate the thermostat, I splice on a length of new cable. For low-voltage wiring like this, no junction box is needed. I use a crimp connector or small wire nuts, and I tape or cable-tie the two cables together to take the strain off the splices. • Before you complete the installation, plug the cable’s hole in the wall with caulk or non-hardening putty. This keeps
cable was used, the colors usually match up: red lead (wire) to the terminal marked “R,” green lead to “G,” yellow to “Y,” and white to “W.” By convention, the red lead is the power supply, green controls the air mover or blower, yellow controls cooling/ air-conditioning, and white controls heat. The simplest programmable thermostat typically has two R-terminals: RC for power from the cool transformer, and RH from the heat transformer. If your cable has only one R lead, connect it to one of the two R terminals, and leave or install
drafts inside the wall from influencing the thermostat.
FOR A NEW INSTALL ATION • Run the thermostat cable to an interior wall close to the return-air location and out of direct sun. • Keep runs of low-voltage cable at least 2 in. away from line-voltage cables. Use 6-conductor, 20-gauge standard thermostat wire unless you are sure that your HVAC unit and thermostat need fewer wires. • Run the cable into the stud bay and
the provided jumper wire between the
through a 3⁄ 8-in.-dia. hole in a 1×6 block
two. If the color of the wires doesn’t match
affixed to adjacent studs, flush to their
the terminal designation, use masking tape
faces. Make a service loop by leaving 2 ft.
to label each wire before you disconnect it.
of cable in the stud bay, taped to the side
• Pull out a few inches of cable, and put a
of a stud.
clothespin or binder clip on the wire to
• Wrap 6 in. of cable around a nail driven
keep it from slipping back into the wall. If
partway into the block. This helps to keep
there isn’t any slack, I wrap some electrical
it from being buried under drywall.
or masking tape around the cable, leaving a tail long enough to stick to the wall. If you’re lucky, there’ll be enough slack in the cable to cut off the bare copper and to restrip. For a clamp-type terminal, strip 184
Lighting and Appliances
Sean Groom is a freelance writer in Bloomfield, Conn. Mark Eatherton, a heating contractor in Denver, provided technical information. “Installing a Programmable Thermostat” is written by Clifford A. Popejoy, a California electrical contractor.
CREDITS All photos are courtesy of Fine Homebuilding magazine (FHb) © The Taunton Press, Inc., except as noted below: p. iii: Charles Bickford (FHb); p. iv: (left & right) Daniel S. Morrison (FHb), (center) Charles Bickford (FHb); p. 1: (left) courtesy © Peter Bastianelli-Kerze, (right) courtesy © Rheem Manufacturing Co. p. 4: Every House Needs an Energy Audit by Jefferson Kolle, issue 200. All photos by Chris Ermides (FHb) except photos on p. 6 (left to right) Daniel S. Morrison (FHb), Charles Bickford (FHb), courtesy © John Curtis, Charles Bickford (FHb) and p. 7 courtesy © What’s Working. p. 12: Home Remedies for Energy Nosebleeds by Bruce Harley, issue 190. Photo on p. 14 courtesy © Kevin Kennefick; photos on p. 15 courtesy © John Curtis; photos on pp. 16 and 18 by Daniel S. Morrison (FHb). Drawing on p. 13 courtesy © Jackie Rogers; Drawings on pp. 14–15, 16 by Don Mannes (FHb). p. 20: Can a Vintage Home be Energy Efficient? by Betsy Pettit, issue 194. All photos by Daniel S. Morrison (FHb). Drawings courtesy © Bob La Pointe. p. 30: Efficient Houses Need Fresh Air by Max H. Sherman, issue 178. Photo on p. 33 by Daniel S. Morrison (FHb); photo on p. 35 courtesty © Aprilaire (www.aprilaire.com); photo on p. 36 courtesy © Fantech (www.fantech.com). Drawings by Don Mannes (FHb). p. 39: A Practical Look at Deep-Energy Retrofits by Martin Holladay, issue 214. Photos on pp. 40, 43, 45, courtesy © Green Building Advisor; photos on pp. 42–43 by Charles Bickford (FHb); photo on p. 44 by Daniel S. Morrison (FHb); photo on p. 45 courtesy © Advanced Energy. p. 46: Upgrade Your Attic Insulation by Mike Guertin, issue 200. All photos by Charles Bickford (FHb) except photo on p. 49 by Krysta S. Doerfler (FHb). Drawings by Dan Thornton (FHb). p. 56: Beef Up Your Old Insulation without Tearing Into Walls by Justin Fink, issue 206. All photos by Dan Thornton (FHb) except p. 60 (left) by Andy Engel (FHb); p. 62 (top right) courtesy © Demilec USA;p. 62 (bottom right) Daniel S. Morrison (FHb); p. 63 (bottom left) courtesy © John Curtis; p. 64 (top) Courtesy © Johns Manville. p. 65: All You Need to Know about Spray Foam by Robert Yagid, issue 204. Photos on p. 66 and p. 67 (top) by Rodney Diaz (FHb); p. 67 (bottom) courtesy © BASF; p. 69 courtesy © BioBased Insulation. Drawings by Dan Thornton (FHb). p. 70: Making Sense of Housewraps by Fernando Pagés Ruiz, issue 177. All photos by Scott Philips (FHb) except magnified photo on p. 73 courtesy © Tyvek; p. 77(bottom right) by Krysta S. Doerfler (FHb); p. 78 (top) by Justin Fink (FHb). Drawing by Dan Thornton (FHb). p. 79: Using Rigid Foam for an Efficient and Dry House by Martin Holladay, issue 213. Drawing courtesy © Steve Baczek. p. 82: Basement Insulation Retrofits by Daniel S. Morrison, issue 206. All photos by Dan Thorton (FHb) except bottom right photo on p. 84 courtesy © Roxul. Drawing courtesy © Steve Baczek. p. 85: Weatherstripping by Matthew Teague, issue 118. Photos on p. 85 (bottom), p. 86, and p. 88 (right) by Krysta S. Doerfler (FHb); photos on p. 85 (top) and left photos on p. 88 by Roe A. Osborn (FHb); photos on p. 87 (top right) and p. 89 courtesy © Dean Della Ventura; left photos on p. 87 by Scott Phillips. Drawings courtesty © Bob La Pointe.
courtesy © Eagle; p. 102 (bottom right) courtesy © Simonton; p. 103 (bottom left) courtesy © Joseph Kugielsky; p. 103 (top right) Randy O’Rourke (FHb); p. 97 Maps courtesy © Energy Star; p. 97 Drawing by Dan Thorton (FHb). p. 104: Do Europeans Really Make Better Windows? by Martin Holladay, issue 213. Photos on p. 104, 105, 106, and top drawing on p. 106 courtesy © Optiwin; bottom drawing on p. 106 courtesy © NFRC; p. 107 courtesy © Marvin; photos on p. 108 (top) and p. 109 by Robert Yagid (FHb); p. 108 (bottom) courtesy © SeriousWindows. p. 110: Installing Replacement Windows by Mike Guertin, issue 185. Photos by Daniel S. Morrison (FHb). Drawings courtesy © Bob La Pointe. p. 118: Is Your Heating System an Energy Beast? by Dave Yates, issue Energy-Smart Homes/Winter 2009. All drawings courtesy © Jackie Rogers except technical drawings on p. 120 and p. 126 courtesy © John Hartman; photos on p. 120 (top right) courtesy © Hardcast; p. 121 courtesy © Dave Yates; photos on p. 122 (top) courtesy © Owens Corning; p. 124 courtesy © York; p. 125 (bottom left) courtesy © Aprilaire; p. 125 (top right) courtesy © Danfoss. p. 128: Finding the Sweet Spot: Siting a Home for Energy Efficiency by M. Joe Numbers, issue 93. All drawings courtesy © Malcolm Wells. p. 136: Cool Design for a Comfortable House by Sophie Piesse, issue Energy-Smart Homes/Winter 2009. Photos on pp. 136, 140, 143, and 144 courtesy © Seth Tice-Lewis; p. 137 courtesy © Peter Bastianelli-Kerze; photos on pp. 138, 141, and 142 courtesy © Michael Sanford. Drawings courtesy © Sophie Piesse. p. 145: Central Air-Conditioning: Bigger Isn’t Better by Chris Green, issue 164. Photo courtesy © John Curtis. Drawings by Don Mannes (FHb). p. 151: Low-Energy Lighting, High-Energy Design by Randall Whitehead, issue Energy-Smart Homes/Winter 2010. Photos on pp. 152, 155 (bottom), 156–158 by Dennis Anderson courtesy © Randall Whitehead; p. 153 (top) courtesy © VU1; p. 153 (bottom) courtesy © MaxLite; p. 154 (top) courtesy © LiteTronics; p. 154 (bottom) courtesy © eW™; p. 155 (top) courtesy © Randall Whitehead. p. 159: The Bright Future of Lighting by Sean Groom, issue 205. All photos by Dan Thorton (FHb) except photos on p. 161 (top left) and p. 164 (top) courtesy © Cooper Lighting; p. 162 (middle left) courtesy © Kichler Lighting. p. 165: The Energy-Smart Kitchen by Alex Wilson, issue 191. Photos on p. 166 courtesy © Maytag Corp.; p. 168 and p. 169 (left photos), p. 170 (top) courtesy © General Electric; p. 169 (right) courtesy © Whirlpool Corp.; p. 170 (bottom) courtesy © Peerless-Premier Appliance Co.; p. 172 courtesy © Fisher & Paykel Appliances; p. 173 (left and center) courtesy © Bosch Appliances; p. 173 (right) courtesy of LG Appliances. Drawings courtesy © Matt Collins. p. 174: Solar Hot Water by Scott Gibson, issue 194. Photo on p. 174 courtesy © Viessmann Manufacturing Co.; p. 176 courtesy © Rheem Manufacturing Co.; p. 179 and p. 180 photos courtesy © Solarwrights Inc.; p. 181 photos by Charles Bickford (FHb). Drawings courtesy © Toby Welles/WowHouse.net. p. 182: Energy-Saving Thermostats by Sean Groom, issue Energy-Smart Homes/Winter 2009. All photos by Scott Phillips (FHb) except center photo on p. 182 courtesy © White-Rodgers.
p. 91: A Buyer’s Guide to Windows by Sean Groom, issue 203. Photos on p. 92 and p. 94 by Rodney Diaz (FHb); p. 101, p. 102 (left and top right) courtesy © Marvin; p. 102 (middle right)
185
INDEX
186
A
B
Accent lighting, 155, 162–64 AFUE (annual fuel utilization efficiency), 124 Air-conditioning systems failure in operating efficiency, size, and installation, rate of, 145 function of, 145–47 how it works, 147 installation of, 149–50 installer, finding a good, 150 large systems, reasons contractors sell, 148–49 reducing the need for, 148 short cycling, 147 size of, 18–19, 145, 147–48 See also Passive cooling Air handlers in attics, 17 Air leaks in the attic, 47–49, 51–53 in the basement, 82–83 chimneys and, 47, 50 ductwork and, 15, 17 in the heating system, 119–20 percentage of a home’s heating and cooling costs attributed to, 65 recessed lights and, 52 sealants for, 49 See also Weatherstripping Ambient lighting, 156 American Society of Heating, Refrigerating and AirConditioning Engineers (ASHRAE), 30, 149 Architectural massing, 13–14 AttiCat, 54 Attic insulation batts, 49, 53 blown-in, 53–55 deep-energy retrofits vs. practical alternatives, 42 payback period for upgrading, 46 priority of upgrading, 57 See also Air leaks Attics access panel or pull-down stairway, 47, 53 air handlers, 17 air leaks, 47–49, 51–53 (see also Air leaks) cost and labor for an upgrade, example of, 55 hidden holes, 13, 14–15 safety when working in, 47 wiring, 49
Backdrafting, 31 Balsam wool insulation, 58 Basements air-sealing, 82–83 insulating, 42–43, 83–84 water management, 82 Blinds, 139 Blower-door tests, 5–6 BTU (British thermal unit), 124
C Calculite (Lightolier), 164 Canada, energy rating for windows manufactured in, 100 Cantilevers, 13–14 Cellulose insulation, 63 Chandler, Michael, 69 CheckMe! (Proctor Engineering Group), 150 Cheimets, Alex, 43 Chimneys, 15, 47, 50 Cold cathode fluorescent lamps (CCFLs), 154 Collins, Brad, 176–77, 180 Color-rendering index (CRI), 161 Compact fluorescent lamps (CFLs), 153–54, 160–61 Cooktops, efficiency and types of, 168–70 Cooper, Gail, 148 COP (coefficient of performance), 123–24 Correlated color temperature (CCT), 161 Cotton batts, 60 Crock pots, 172
D Decorative lighting, 155–56 Deep-energy retrofits, 39–41 basement insulation, 42–43 costs and payback of, 41 HVAC, 44–45 phases of, 41 results, examples of, 43, 45 roof insulation, 42 wall insulation, 44 windows, 44 Dishwashers, 171–73 Doors, weatherstripping options for, 87 Duct blasters, 6, 8
Ductwork balancing, 123 sealing, air leaks and, 15, 17, 119–20 types of, 122
E EER (energy-efficiency ratio), 124 Eldrenkamp, Paul, 42 Electric wiring, in attics, 49, 52 Electron stimulated luminescence (ESL) lighting, 153 Energy audits costs and reports, variation in, 10–11 free audits by local utility companies, 8–9 the future of, 11 hiring a qualified auditor, 8–10 for new homes, 8–9 online, 10–11 scientific, 5–7 unscientific but learned assessments, 4, 6 Energy efficiency, 3 durability and, 23 in older homes (see Old houses) of ovens, by type of, 170 siting a home for (see Siting a home) tools to measure, 166 Energy factor (EF), 172 EnergyGuide stickers, 166 Energy Independence and Security Act of 2007, 159 Energy leaks architectural massing and, 13–14 framing and, 13–16 insulation and, 14 (See also insulation) subcontractors’ responsibilities and, 12–13 Energy-recovery ventilator (ERV), 36–37 Energy-saving thermostats, 182–84 Energy Star program energy audits and, 9, 11 ratings for appliances, 166, 167, 172 ratings for windows, 97–99 rebates, 127 Exhaust fans, 171 Expanded polystyrene (EPS), 61, 79, 84 Extruded polystyrene (XPS), 61, 79, 84
F
I
Fiberglass insulation, 59 batts, 49, 53 blown-in, 64 Fisette, Paul, 71–72 Foam pour, 62 rigid, 61, 79–81, 84 spray (see Spray foam) Framing, holes constructed during, 13, 14–15
Infrared thermographs, 7 Insulation amount needed, calculation of, 27 attic (see Attic insulation) basement (see Basements) removing, 60 roof, 42 sources of, 64 spray foam (see Spray foam) substandard work by installers, costs of, 13, 14 types of, 56–64 ventilation and, 141 (see also Ventilation) in walls (see Walls) in windows, 95–96
H Haitz’s Law, 162 Harley, Bruce, 68, 147 Heat. See HVAC (heating, ventilation, air-conditioning) Heat Mirror glazing, 108–9 Heat-recovery ventilator (HRV), 36–37 Home-energy rating system (HERS), 8 Hot water. See Solar hot water Housewrap, 70 chemical compatibility of, 76 choices for, 72–77 evaluating performance of, 71–72 felt paper as, 75 functions of, 70–71 installation as key, 77–78 seam tape and fasteners for, 78 siding material and, 74 HSPF (heating seasonal performance factor), 123–24 Humidity, 149 HVAC (heating, ventilation, airconditioning) air-conditioning systems (see Airconditioning systems) boiler basics, 126 deep-energy retrofits vs. practical alternatives, 44–45 ductwork (see Ductwork) furnace basics, 120 furnace service call, 121 heating system questions and answers, 119, 121–25, 127 heat-pump basics, 122 heat sources for U.S. households, 118 passive cooling and, 143–44 programmable thermostats and, 182 replacing a furnace, decision regarding, 127 substandard work by installers, 13 terminology of, 124 ventilation (see Ventilation) See also Passive cooling
J Jensen, Dustin, 9 Johnson, Eric, 163–64
K Kemp, Clarence, 174 Kitchens cooktops and ovens, 168–70 dishwashers, 171–73 electricity consumption in, 165 exhaust fans, 171 lids, use of, 171 microwave ovens, 170–71 refrigerators, 166–67 Kleiman, Elia, 177 Klingenberg, Katrin, 107 Kneewalls, 13, 16
L Lead paint, 112 Light-emitting diodes (LEDs), 154, 161–63 Lighting bulb technologies, 153–54 color of good, 161 compact fluorescent lamps (CFLs), 153–54, 160–61 efficacy as a measure of efficiency, comparing fixtures using, 163 energy-efficient, attitudes and realities regarding, 151–52 energy-efficient decorative fixtures, sources for, 158 focused, need for, 163–64 the future of, 159–60 layering, new technologies and, 152–53 light-emitting diodes (LEDs), 154, 161–63 sources for, 154, 164
stealth lighting, hiding energyefficient bulbs through, 156–58 types of, using varied, 154–56, 163 Luxton, Steve, 7
M MacKensie, Leslie, 4 Merrigan, Tim, 177, 179–80 MERV (minimum efficiency reporting value), 124 Microwave ovens, 170–71 Mineral-wool batts, 84 Moisture in basements, 82–83 exterior foam as vapor barrier, 81 hot and humid climates, options for, 34 housewrap and, 70–71 Moore’s Law, 162 Motorized dampers, 125
N National Fenestration Rating Council (NFRC), 95, 100, 105 Net-zero energy use, seven steps to, 22–23
O Old houses air leaks as ventilation in, 30–31 case studies of renovations, 21–23 cost of renovating, 21 durability and energy efficiency, relationship of, 23 first renovation, insulation and moisture control in, 24–25 net-zero energy use, seven steps to, 22–23 renovating, 20–21 second renovation, insulation and moisture control in, 26–27 third renovation, insulation in, 28–29 Ovens efficiency by type of, 170 electric vs. gas, 168 microwave, 170–71
P Paradigm Windows, 109 Passive cooling, 136 energy-efficient mechanical systems and, 143–44 insulation and, 141 passive solar vs., 137
Index
187
siting: face the sun, shade the glass, 137–39 (see also Siting a home) sources for solar professionals, 144 thermal mass and, 141–43 ventilation, 139–41 Permeance ratings, 71–72 Pfeiffer, Peter, 68 Polyisocyanurate (POLYISO), 61, 79, 84 Porter, Chris, 67 Price-Jones, Cador, 45 Programmable thermostats, 182–84
R Radiant reflective membrane, 46–47 Recessed lights, 52 Refrigerators, 166–67 Renovating older homes. See Old houses Replacement windows, 110 choosing, 103, 111, 114–15, 117 evaluating existing windows, 110–11 installing, 114–15 measurements and sizing of, 116–17 removing existing windows, 112–13 Residential Energy Services Network (RESNET), 8–9 Rim joists, 13, 32 Rock wool insulation, 59 Rudd, Armin, 149–50 Rutkowski, Hank, 148
S Safety attics, when working in, 47 of spray foam, 65–66 SEER (seasonal energy-efficiency ratio), 123–24 Siting a home, 128–29 hillside lots, 130–31, 132 house shape and climate, matching, 133–35 more information on, 135 southern exposure for long side, 129–30 sun, orienting to, 130–31, 137–39 wind, taking advantage of, 131– 33, 134 Solar energy, information resources, 181 Solar heat gain coefficient (SHGC), 97–100, 105
188
Index
Solar hot water active systems, 179 basics of, 175–76 cost of, 178 energy crises and, 174–75 financial incentives, 179–80 hot water usage, 176–77 indirect systems, 180 installing collectors, 181 passive systems, 175 passive thermosiphons, 176 Solar space heating, 177, 179 Spray foam cost, 69 durability, 18 for the eco-conscious, 69 installing, two approaches to, 68 open-cell vs. closed-cell, 66–67 safety/toxicity, 65–66 as sealant, 49, 65 sources of, 69 thickness of installed, 67, 69 Superinsulation retrofits. See Deepenergy retrofits
T Task lighting, 154–55, 162–64 Thermal mass, 141–43 Thermostatic radiator valves, 125 Thermostats, energy-saving, 182–84
U Urea-formaldehyde foam insulation (UFFI), 58
V Vented roofs, 16 Ventilation approaches to good, 32 balanced, 36–37 breathe, tight houses need to, 38 definition of, 30 exhaust, 32–34 filters for large particles, 37–38 house pressure and air movement, 31 insulation and, 141 (see also Insulation) leaky houses and, 30–31 passive cooling and, 139–41 pollution of indoor air, 31–32 residential standards, 37 supply, 34–35 tempered air, 38 tight houses and poor indoor-air quality, problem of, 30 See also Moisture Vermiculite insulation, 58–59 Visible transmittance (VT) rating, 100
W Walls discovering what’s inside, 59 exterior, rigid foam for, 79–81 insulating, 44, 56–57 insulation upgrade options, 61–64 removing insulation from, 60 types of insulation in, 56–60 Water heaters, 19 Weatherstripping, 85 door sweeps, 90 door thresholds, 89–90 felt, 86 interlocking metal, 88–89 kerf-in, 88 options for windows and doors, 87 pressure-sensitive, adhesivebacked tapes, 86 rigid jamb, 85 sources for, 87 V-strips, 86 Windows anatomy of, 94 coatings, 97 comparing European and American, 104, 106–7 deep-energy retrofits vs. practical alternatives, 44 energy efficiency, significance for, 19 energy-saving, choosing, 97–100 European, 105–8 films, 100 frame materials, 91–93 frame quality, evaluating, 93, 95 functions of, 91 impact-resistant glass, 101 insulated glass, 95–96 natural light, 100 NFRC label, reading the, 95 North American, 108–9 performance of, 105 privacy and acoustic, 101 replacement (see Replacement windows) self-cleaning, 101 site-specific approach to choosing, 100 sources for, 103, 109 spacers, 96–97 styles of, 101–3 U-factor, explanation of, 96 weatherstripping options, 87 Wraparound porches, 13–14
HOUSE & HOME
Be Energy Smart Conduct an energy audit Upgrade your attic insulation Install replacement windows Choose the right housewrap Buy the best new windows
We’d all like to cut do n on home energy use, and, if possible, to cut down on energy bills. The Energy-Smart House, from the editors of Fine Homebuilding, shows you ways to do just that. From conducting an energy audit—the first step for any homeowner trying to improve on energy efficiency—to chapters on insulation, windows, heating and cooling, lighting, and appliances, The Energy-Smart House provides all the advice you’ll need to become an energy-smart homeowner. With expert advice from the leaders in the field, The Energy-Smart House includes articles on the methods, materials, and technology needed to help make your home more energy efficient and to ensure that you cut back on both home energy use and energy bills.
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