Renovation 4th Edition
Page 90
housewrap, or building paper and, increasingly, rigid insu-
The nagging feeling that if you don’t whip your
lation; interior air barriers are usually drywall. In either
house into airtight, energy-sipping, good-as-
case, sealing the seams and gaps of materials in the build-
green shape right now, you’re not doing your
ing envelope is the key to making air barriers continuous
part. Fact is, an all-at-once deep energy retrofit
and airtight.
that cuts energy use 50% to 90% can cost
*Spray foam and rigid-foam panels effectively stop
$100,000 and up.
airflow and may not require separate air barriers.
Energy Conservation and Air Quality
385
GETTInG GREEn
and a few passive intake vents (p. 400). The only
downside of this solution is that it draws uncon-
wITHouT GoInG BRokE
ditioned air into the house, which will need to be
The good news is that you don’t have to get green heated (or cooled). The solution to that waste of
all at once. With planning, patience, and paying
energy, a somewhat more costly and complicated
as you go—rather than going into hock—you can fix, is incorporating a heat-recovery ventilator
lower utility bills incrementally and feel good
(HRV) into the house’s HVAC ductwork. There’s
P R O T I P
about the progress you’re making. It’s still a green an illustration of an HRV system on p. 403 but, in
path; it just meanders a bit more.
brief, an HRV uses the heat of stale exhaust air to
If the attic is insulated, you’ll
The nine steps below are a logical progres-
temper fresh incoming air.
need to put on gloves and a face
sion—which renovations rarely are. So if your
Step 4: Insulate, starting at the top. Because
mask and move that insulation
home has a pressing need, tend to that first, and
hot air rises, few energy retrofits are more effec-
before you can seal openings in
as you do so, try to find solutions that will
the attic floor. But don’t merely
tive than insulating an attic or roof. If you need a
improve the energy profile as well. In the remodel
cuss those batts; examine them.
new roof, stripping it and installing rigid-foam
described on p. 40, for example, the homeowners
Fiberglass batting actually filters
panels before reroofing is a pricey but premium
had a drafty house with asbestos siding. After
dirty air, so look for blackened
route to take. If you want to convert the attic to
stripping the siding, they built up 2x4 studs into
areas on the undersides of
living space, spraying foam to the underside of
2x6s, sealed air leaks, and insulated—all from the
batts, where heated air has
the sheathing is a viable and less expensive way
exterior. This, in turn, meant that interior finish
blown through ceiling cracks
to insulate from the inside. But if your attic is
surfaces were undisturbed.
into the attic.
unfinished and accessible, blowing in cellulose is
The rest of this chapter more or less follows
hands-down the most cost-effective way to go—
this sequence—with the exception of upgrad-
after you’ve sealed drywall gaps, pipe chases,
ing windows, which is covered at length in
electrical penetrations, the framing around the
chapter 6. So search below for a fuller explana-
chimney, and so on. Especially in cold climates,
tion of most steps.
more is better: Roughly 17 in. of blown-in cellu-
Step 1: Get an energy audit. A thorough energy lose will get you an R-60 attic floor.
assessment is essential because it’s a specific
Step 5: Insulate inside the basement.
analysis of your house. Using diagnostic equip-
Basement walls are an easy energy retrofit
ment such as blower doors, duct blaster fans
because they’re accessible. Insulating rim joists
and infrared cameras, audits can pinpoint where
and basement walls is worth the money in the
heated or cool air is escaping. If mechanical
Cold Belt; less so in sunny climes unless you want
ventilation is needed, an audit will note that, too. to convert the basement to conditioned living
After the inspection, you will get a report that
space. In either case, correct moisture problems
includes the home’s energy rating, along with an
first. If you can’t afford to insulate the walls, do
estimation of annual energy use and costs. The
insulate the rim joists. To insulate basement walls,
report will usually include recommended energy
use rigid-foam panels, as described on p. 417.
retrofits and their costs, as well as the potential
Heat loss through floors is negligible, so insulat-
annual savings and probable payback times for
ing them makes little financial sense unless you
each improvement.
intend to install a finish floor over the concrete.
Step 2: Seal air leaks. It has been estimated
Step 6: Upgrade wall insulation. If you’re gut-
that up to 30% of the heat loss in some houses
ting finish surfaces and exposing studs, insulat-
is due to leaks in the thermal envelope, so air-
ing walls is a romp. Dense-pack cellulose and
sealing should always precede insulation. In a
fiberglass batts are both effective. More often,
“gut” renovation when the sheathing is exposed,
older homes have some wall insulation, but it has
it’s a straightforward task to seal building seams
settled or was never installed uniformly. Blower-
and openings. In a selective retrofit, an audit is
door and smoke-stick testing and thermal imag-
invaluable in tracking down elusive leaks, such as ing can show cold spots that need air-sealing and
gaps where drywall panels don’t quite meet,
supplemental insulation. Typically, insulation is
under or over wall plates, around the perimeter
added by prying up siding, drilling holes in
of the attic, and around openings for electrical
sheathing, blowing in dense-pack cellulose or
outlets or plumbing penetrations.
injecting foam, plugging holes, and restoring sid-
Step 3: Add or upgrade mechanical ventila-
ing. It can be cost-effective, but takes great skill
tion. Once you’ve cut infiltration by sealing air
to do a thorough job that doesn’t look piecemeal.
leaks, stale air may build up inside the house.
Step 7: Replace or upgrade windows.
This problem can be remedied inexpensively,
Replacing all single- or double-pane windows
however, by adding a whole-house exhaust fan
with high-efficiency, full-thickness (13⁄8-in.) triple-
not much bigger than a standard bathroom fan
386 Chapter 14
pane windows is a huge expense: Installed, new
units cost $900 to $1,200 each. Those without<
br />
EnERGy Rebates And IncEntIvES
tens of thousands of dollars on hand might
choose instead to replace one wall of windows at
Renovators looking for ways to finance energy retrofits should start at the Department
a time or, yet more frugally, to weatherstrip exist-
of Energy’s website, www.energy.gov.
ing windows and then install low-e storm win-
From there you’ll find additional links and descriptions of federal, state, and
dows. Good-quality storm windows can achieve
private programs:
about half the U-factor of new windows at roughly
Approved Energy-Efficient Appliance Rebate Programs: www.energysavers.gov/
one-sixth the cost.
financial/70022.html
Step 8: Upgrade your heating system.
Database of State Incentives for Renewables and Efficiency: www.dsireusa.org
Compared with the cost of replacing windows,
Energy-Efficient Mortgages and Financing: www.energysavers.gov/financial/
installing a 92% AFUE (annual fuel-utilization
index.cfm/mytopic=70030
efficiency) furnace for $4,000 to $6,000 seems
This last site has additional links to:
like a bargain. It’s not higher on the list because
Financing an Energy-Efficient Home: www.energysavers.gov/your_home/
without improvements to the thermal envelope
designing_remodeling/index.cfm/mytopic=10380
you’re not making the most of the investment.
This fact sheet from the Department of Energy features an overview of energy-
Further, by tightening the house you can reduce
efficient financing programs from mortgages to home improvement loans.
the size of a new furnace or boiler. If you want to
save money beforehand, seal leaky ductwork,
U.S. Department of Housing and Urban Development: Energy-Efficient Mortgage
guided by the Duct Blaster® testing of your ener-
Program: http://portal.hud.gov/hudportal/HUD?src=/program_offices/housing/sfh/
gy audit. Sealing and repairing ducts is relatively
eem/energy-r
cheap—$300 to $400—and in winter months can
The Energy-Efficient Mortgage Program is one of many Federal Housing Authority
save up to 20% on utility bills.
programs that insure mortgage loans to encourage lenders to make mortgage credit
Step 9: Install renewable energy devices. A
available to borrowers, such as first-time homebuyers, who would not otherwise
solar panel or some other renewable-energy
qualify for conventional loans on affordable terms.
device may be part of your new HVAC system.
Energy Ratings and Mortgages: www.resnet.us/home-energy-ratings
More commonly in retrofits, solar hot water or
Energy-efficient homes may qualify for mortgages that take into account a home’s
photovoltaic panels that generate electricity can
efficiency. Residential Energy Services Network (RESNET) provides information on
supplement an existing system. Incorporating
home energy rating systems, energy-efficient mortgages, and finding certified energy
renewable components into existing HVAC sys-
raters and lenders who know how to process energy-efficiency mortgages.
tems can be a costly and complex undertaking,
Refinancing for Energy-Efficiency Improvements: http://ase.org/topics/saving-
but, presently, there are a number of federal and
money-and-energy
state incentives for renewables, including energy-
An overview of refinancing to make energy-efficiency improvements from the
efficient mortgages and financing, as explained
Alliance to Save Energy.
at right. Passive solar designs reduce energy costs
by taking advantage of solar energy. Although the
basic ideas are fairly simple, putting them into
practice can be complex, requiring the help of a
design professional.
Getting an Energy Audit
Improving a home’s energy profile begins with a
homeowners have access to incremental rebates,
careful diagnosis of where it’s losing heat. This
based on the number of energy-saving measures
diagnosis can be intuitive, based on years of
they implement. As of 2010, 25 states had adopted
remodeling houses. Most energy loss is due to air climate action plans to reduce greenhouse gases,
infiltration, after all, and old houses leak air in
so many cities now require energy audits as part
predictable places—attic floors, for example.
of the permit approval process. Typically, energy
Moreover, you can feel cold air entering a leaky
audits are triggered by some combination of a
window on the back of your hand. Yet as building project’s size and valuation—say, a project size of
science has become more pervasive, the pressure 500 sq. ft. or more and a $50,000 budget.
for rigorous scientific audits has become irresist-
Lastly, there are emerging state and federal
ible. That trend will continue as energy prices
incentives for energy-efficient mortgages and
continue to rise.
financing, all of which require energy ratings as a
Regulations and incentives have also increased condition for lending (see above). It’s worth not-
the need to verify causes—and remedies—in a
ing that bank loan officers who keep abreast of
scientific manner. From federal tax credits and
such programs also smile on energy-efficient
programs to state or utility incentives, many
mortgages because borrowers with lower monthly
Energy Conservation and Air Quality
387
Blower-door testing helps quantify
envelope has been tightened, blower-door testing
the amount of conditioned air (and
is also an essential tool to determine if a house
hence energy) being lost through
needs mechanical ventilation and to make sure
leaks. As the blower depressurizes the
that combustion appliances have adequate air
house, outside air is pulled in through
supply and that running bath fans, range hoods,
holes in the thermal envelope.
and other fans won’t cause backdrafting.
SMokE pEnCIlS And
THEATRICAl SMokE
When the house is depressurized, an auditor may
use a smoke pencil (also called smoke toys or
smoke sticks) to help make individual air leaks
visible. Smoke pencils emit a chemical smoke, so
you can see the air being pulled in through leaks.
Theatrical smoke, as the name implies, is a drama-
tic volume of “smoke” generated by a theatrical
fog generator, primarily used to indicate duct leaks.
Who requests the audit usually determines
how the information is used. When a homeowner
gets an audit to satisfy a city planner or a mort-
gage lender, the smoke demonstration is usually
educational. Seeing air leaks in unexpected places
utility bills are better loan prospects and their
often convinces homeowners that they need to
homes are more highly valued than comparables
spend a little more to get a tighter house. If, on
that waste energy.
the other hand, an auditor is working with a home
Now let’s look at diagnostic tests that may be
performance contractor, the blower door, smoke
part of a scientific home energy audit, which
pencil, and thermal images shown here are used
takes four to six hours to complete.
to direct the retrofit work. Typically, the blower
BlowER-dooR TESTInG
keeps running as the crew seals air leaks—until a
targeted (lower) leakage rate is attained.
Because air infiltration is the major cause of
energy leaks, auditors first try to quantify the vol-
THERMAl IMAGInG
ume of air being lost. After closing exterior doors An infrared camera’s ability to see invisible
and windows, turning off combustion appliances sources of heat loss can inform even a pro,
such as furnaces and gas water heaters, closing
whether he’s trying to track down elusive air leaks
flues and shutting fireplace dampers, the auditor
or develop a retrofit strategy. Thermal images
uses a blower door to depressurize the house.
This pulls outside air into the house, in effect
exaggerating the holes in the thermal envelope.
A blower-door assembly includes an airtight,
expandable frame, a calibrated fan, and a
manometer—a pressure gauge with two chan-
nels. One of the manometer channels measures
the difference between inside and outside pres-
sure, while the other measures the difference
between the calibrated fan and the inside. The
door fan blows air out of the house until the pres-
sure difference reaches 50 pascals (Pa), a stan-
dard reference basis. Once pressure readings are
steady, the manometer calculates the total flow of
all leaks in the house. That airflow can be mea-
sured as air changes per hour (ACH) or in cubic
feet per minute (cfm).
Getting an aggregate figure for house air leak-
age will suffice for some audits, but a blower-
door fan can also be used in tandem with other
devices to help pinpoint leaks, as described
below. It’s important to note that once the house
A smoke pencil helps make air leaks visible.
388 Chapter 14
show not only air leaks but also settled or absent
insulation and thermal bridging (heat loss through
relatively poor insulators, such as framing). It
can also help locate and identify moisture issues.