The images indicate temperature differences
between surfaces, so the camera is most effec-
tively used when there is a temperature difference
of at least 10°F from the inside to the outside.
Using a blower door in conjunction with the
infrared camera can help accentuate and locate
problem areas.
Infrared cameras have become more common
as they’ve become more affordable ($1,500 to
$5,000), but interpreting the information can be
subtle. Generally, darker colors indicate cold air,
whereas lighter hues indicate warm air. With a
typical color palette, cold air leaks tend to appear
as blue fingers. As with any tool, using an infra-
red camera takes training and practice, without
which results can be difficult to interpret.
duCT TESTInG
Take thermal images in early morning, when the temperature differences (delta T) between inside
Duct testing is important because leaky ducts
and outside air are the greatest. The greater the delta T, the greater the color contrasts in the
can be responsible for as much as 30% of lost
thermal image.
energy, to say nothing of heat-starved rooms or,
in some cases, a buildup of carbon monoxide in
living spaces.
The auditor starts by temporarily sealing
heat registers and supply grilles. He connects a
variable-speed duct blower to a central air return,
a supply plenum, or the HVAC system’s fan cabi-
net. You can test ducts without pressurizing the
inside of the house. However, as Donn Davy of
www.greenhomesavvy.com points out, “If one
pressurizes the interior of the house to 25 pascals
and then adjusts the duct to equalize that pres-
sure in the duct system, the reading will reflect
‘leakage to the outside,’ which is more useful for
calculating real energy losses, since leakage with-
in the envelope still heats (or cools) the interior,
just not as effectively.”
To find and fix individual leaks, a theatrical
fog generator is often placed next to the duct
blower. Ducts fill with “smoke,” which then
escapes out of duct connections, missing end
caps, faulty register-to-boot seals, or leaky con-
nections at the plenum. Occasionally, flexible
ducts in crawlspaces get crushed or gashed by
clumsy “repairmen,” and some types of older
flexible ducts degrade over time and develop
holes and tears. Predictably, the largest leaks are
sealed first, with special attention given to leaks
Leaky ducts in a forced hot-air system can squander energy.
in return-ducts near combustion appliances such After sealing heat registers and air intakes, an energy auditor
as gas water heaters. There, leaking ducts could
uses a fan to pressurize the ductwork, sometimes blowing
create negative pressure, pulling dangerous flue
theatrical smoke as well, so technicians can see just where
gases back into living spaces. Sealing ductwork is ducts are leaking.
covered on p. 396.
Energy Conservation and Air Quality
389
TESTInG CoMBuSTIon And
gobble more than two-thirds of the kitchen total.
Ovens, microwaves, cooktops, and dishwashers
HouSEHold ApplIAnCES
account for the remaining third.
Because heating and cooling appliances can affect
energy costs, health, and safety, many home
THE AudIT REpoRT
audits include those devices, as well as gas-fired
Reports vary, but those based on a whole-house
water heaters. According to a GreenHomes®
energy audit such as the widely used HERS-II*
America spokesman, “We see potentially serious
(home energy rating system) will typically include:
combustion safety and gas leak issues in as many
An energy-efficiency rating that places
as 25% of the homes we visit before we touch
the house along a continuum, with a 0 rating
anything. And equipment that has poor or mar-
(net zero) meaning that the house’s net
ginal draft before an air-sealing—or any retrofit
purchased energy is zero, and a 100 rating
project—can be made even worse. Carbon mon-
indicating that it meets 2008 IRC energy specs.
oxide is deadly, and even chronic low levels can
Ratings for most existing homes are
make people sick.”
considerably above 100, showing a need for
Auditors use digital combustion analyzers to
improvements. HERS ratings are helpful to
see how efficiently your furnace, boiler, or gas
homeowners because they can see, at a glance,
water heater is consuming fuel. Such tests can
their home’s relative efficiency.
also detect problems within a furnace, such as a
Scoring individual components. The
cracked heat exchanger, which could allow
aggregate HERS score is broken down to show
exhaust gases to enter ducting—and living spaces. the efficiency of each house system. Based on
To test the draft in flue pipes, the auditor will
the auditor’s diagnostic tests, the report
shut all doors and windows, turn on all exhaust
includes duct leakage, ACH or cfm numbers,
fans in the house in an attempt to create negative insulation R-values, windows’ solar heat gain
pressure, and then insert a digital probe into the
coefficient (SHGC) ratings and U-values,
flue pipe. A good auditor will also look for telltale furnace AFUE scores, and so on. A companion
signs of earlier backdrafting, such as rust or
document, usually software generated,
scorch marks near the draft hood of a furnace or
explains scores and industry acronyms at
water heater. Audits with health and safety com-
greater length and suggests probable savings
ponents routinely check gas pipe and meter con-
based on improvements such as, say,
nections for leaks as well.
increasing roof insulation.
A thorough audit will also employ electricity-
usage monitors to determine how efficient house-
Auditor’s recommendations. Here,
hold appliances are. Kitchens are fertile testing
skilled and personally committed auditors can
grounds: They account for nearly 30% of the util-
really shine. Having gotten to know you and
ity bill, and refrigerators and freezers together
your house, they can make specific
recommendations on where you should spend
to improve efficiency, safety, health, and
comfort. For example, “If you want to get
serious about air quality—which makes sense
with a 2-year-old in the house—I would seal
the crawlspace with plastic sheeting, 9-mil or
better.” Above all, an auditor’s recommend-
ations should be objective, putting
homeowners’ needs above anything else.
* In California, there are two types of HERS
reports: One has to do with Title 24 verification,
relat
ing to 14 measures in the energy code. HERS-
II is a whole-house verification, projecting how a
house will use energy over the years.
How To FInd An EnERGy AudIToR
The best way to find a reputable energy consul-
tant, architect, or contractor is to ask a building
professional whose opinion you trust. Two com-
panies that have helped develop energy-auditing
Digital combustion analyzers see how efficiently a furnace, boiler, or gas water heater is consuming standards now certify independent auditors and fuel. An audit may also test the draft in flue pipes.
390 Chapter 14
A whole-house energy audit, such as
the HERS-II (home energy rating
system) report shown here, will
typically rate a house’s energy profile
so homeowners can see at a glance
how energy-efficient their home is.
maintain databases of consultants. They are the
Air-Sealing
Residential Energy Services Network (www.
As noted early in the chapter (“How Heat
resnet.org) and Building Performance Institute
Moves”), most insulation achieves its full R-value
(www.bpi.org). The Department of Energy’s
only when used with an air barrier. Air leaks
Energy Star website, www.energystar.gov, also
allow conditioned air to escape, but they also
has a list of certified auditors and contractors.
prevent insulation from doing its job. In new
Given the growth in energy audits, a number
construction—or when gutting finish surfaces
of contractors have become home performance
in a renovation—installing a continuous air bar-
contractors who do both the audits and the
rier is a straightforward task because access is
remedial work. This niche is so promising that
easy. But in most energy retrofits, upgrading the
GreenHomes America, which offers energy
air barrier means finding air leaks in the build-
audits, does retrofit work, and helps homeowners ing envelope and sealing them one at a time. As
“secure low-interest financing or government…
tedious as this task can be, it’s time and money
incentives to offset the cost”, will soon have
well spent because, dollar for dollar, sealing air
26 locations in 14 states.
leaks is the most cost-effective energy retrofit
The question invariably arises: Can a company you’ll undertake—especially if the attic is uncon-
doing the work also be an unbiased auditor?
ditioned (unfinished and unheated). Air infil-
Clearly, an independent energy auditor has fewer tration can account for 20% to 30% of energy
conflicts of interest. But it has become clear that
losses, especially when a home has fiberglass
more energy retrofits are actually completed
batts or cellulose insulation.
when homeowners hire a combined auditing-
contracting company. Having one entity oversee
CAulkS, SEAlAnTS, And oTHER AIdS
the retrofit and sift through a slew of government
incentives simplifies things for homeowners.
Because this section is about sealing air leaks,
Careful air-sealing takes a lot of
So does knowing exactly whom to call if you’re
sealants is probably the best overall term for dif-
time—and many cans of expanding
not happy how the work was done. Whatever
ferent materials that stop air infiltration. Most of polyurethane spray foam. Local codes
auditing-contracting model you choose, interview
may require the use of fire-rated
us use caulk or caulking when filling building
foams to seal penetrations and gaps
carefully, call references, check the company’s
gaps and cracks, but here let’s use “caulk” to
that could become fire updrafts.
record with the state licensing board, and get a
denote a flexible sealant that is squeezed out of a
second opinion if ever you’re feeling pressured
tube and doesn’t expand to fill the gap or crack.
or uncertain.
By the way, sprayed-on foam insulation—
sometimes called flash foam—is often used to
Energy Conservation and Air Quality
391
insulate and air-seal building seams but I’ll dis-
Polyurethane foam sealants expand to fill gaps.
cuss it in the following section on insulating.
They are the workhorses of air-sealing, typically
applied using 12-oz. to 33-oz. aerosol cans with
caulk choices. Caulks are covered in chapter 4,
straw-type applicators. Though their formulas
so let’s keep it short and specific here. Caulks are
vary slightly, for the most part they are rigid once
best used for gaps less than 1⁄2 in. wide; for wider
cured, so they should not be used to fill gaps that
gaps, start with a foam backer rod, then apply
will be subject to movement. They should not be
caulk. Surfaces being caulked need to be clean,
exposed to weather or used outside. Important:
stable, and dry or the caulk may not stick.
All foam sealants expand, and some so aggres-
Scraping away flaky substrates, blowing or wip-
sively they can bow window frames. When
ing away dust, and drying the surface are impor-
choosing a foam, first decide whether the task
tant prep steps. Important: Caulks have become
requires low-, moderate-, or high-expanding
extremely specific, so choose a type well suited to foam. By naming foam products for their intend-
your task. Here’s an overview of general categories:
ed uses—“Windows and Doors,” “Gaps and
Water-based caulks, which include latex,
Cracks,” “Maxfill,” “Fireblock”—manufacturers
vinyls, and acrylics, are easy to work with and
have made choosing a little easier.
probably the best choice if you’re sealing
Because foam sealants make contact when
around interior door and window casings and
they’re wet and then expand to fill the space, sur-
other moldings. Because they are so easy to
face prep is not as critical as it is with caulks to
clean up, you can use a wet finger to tool
ensure adhesion. Ideally, though, the surface
(shape and compress) caulk joints. They can
should be stable (not loose) and reasonably free
be painted.
of debris. And there’s a limit to the width of the
Silcone-based caulks are famously
gaps they can fill, so if a gap is wider than 1 in.
tenacious, weather well and stay flexible,
you may want to first pack it with loose fiber-
adhere to many different substrates, and aren’t
glass and then seal it with foam. For the most
affected by UV rays. Solvent-based, they can be
part, foam sealants are benign, but read the
difficult to work with. Pure silicone can’t be
labels and take appropriate safety precautions,
painted, but siliconized acrylics can be.
including adequate ventilation, turning off pilot
Synthetic-rubbe
r caulks adhere well and
lights and not using around open flame, and
stay stretchy, so they are a good choice for
wearing a respirator and safety glasses.
sealing gaps in exterior trim and wood siding.
Weatherstripping, discussed at length in
Once cured, they can be painted with latex.
chapter 6, is the sealant of choice when a gap or
Note: They are volatile until they cure. Wear a
opening will be subject to movement, such as the
respirator when applying, don’t use them
perimeter of an attic hatch, a basement’s bulk-
indoors, and check local VOC regulations to
head door, or a leaky basement window. Tubular
see if they’re allowed.
stripping made of neoprene or sponge foam can
Modified silicone polymer caulks are as
be compressed to seal out drafts.
easy to work as latex and as tenacious as
silicone. They stay flexible in cold weather, can
Foam outlet and switch plate gaskets can be
be painted with water-based paints, don’t
quickly installed beneath the cover plates of elec-
shrink, and aren’t as volatile as synthetic
trical receptacles and switches. Typically the
rubbers. They are the most expensive caulks,
gaskets are sponge foam or, in tech-speak,
however, and don’t have as long a track record
“UL-listed, cross-linked close cell polyethylene
as the others.
insulating foam.” Bought in bulk, they’re cheap
enough to use throughout the house.
Sprayable caulk is intended to seal new-building
seams before installing fiberglass batts, but it
might be a fast way to seal gutted walls or an
addition. There are presently two brands of
Fire-Blocking cAUlkS And FoAmS sprayable caulks—EnergyComplete™ and
EcoSeal™—both developed by fiberglass insula-
Holes in an attic floor allow heated air to escape from conditioned spaces and so
tion makers. Both caulks are quite thick and
waste energy. In the event of a fire, penetrations in top plates especially can hasten
must be applied by high-pressure sprayers to the
the spread of fire from one floor to the next. To fill such penetrations, local codes may
inside of stud bays, as shown in the top photo on
specify fire-barrier (fire-blocking) foams or caulks. Being intumescent, these caulks
the facing page.
and foams expand when exposed to superheated air and can withstand direct flame.
Neither product touts any appreciable
Renovation 4th Edition Page 91