If high energy bills are causing
you shock and frustration, take
heart. There’s something you
can do — call your local utility company
and ask for an energy audit.
An energy auditor will come to
your home and conduct a series of
tests to provide detailed information
about your home's energy usage and
energy loss. A report, generated at the
conclusion of the two- to three-hour
audit, will detail:
• the condition and efficiency of
your heating and cooling system
• the overall efficiency of
your home, including the primary
areas of air leakage in your walls
and ceilings
• low-cost ways you can improve
energy efficiency and save energy
• larger upgrades that will pay back
their cost with energy savings within
a relatively short period.
In this article, we'll walk you through
a professional energy audit and show
you how it works. An audit typically
costs $250 to $400, but most utility
companies offer a rebate to reduce the cost to you. We worked with
Erik Lindberg, a Minnesota
state certified energy auditor,
whose company,
Enervision, has performed
more than
12,000 audits. The
house we audited
was built in 1979.
Erik Lindberg, Certified Energy Auditor
“An energy audit
addresses five priorities:
First is home safety. If your house isn’t safe, energy efficiency
doesn’t matter. Second is durability. Finding and fixing moisture
problems and rot helps the house last longer. Third is comfort.
The audit identifies drafts and cold spots. Fourth is to set up
the best action plan to make your home more efficient,
especially things you can do yourself. Fifth is cost benefit,
which tells you what it’ll cost to make improvements, and
how long it’ll take for the savings to pay off those costs.”
Checking heating and hot water systems
The audit starts with a furnace combustion
efficiency test. With the furnace
running, Erik inserts a gas analyzer in
the furnace's draft diverter (Photo 1). If
there's no draft diverter, he drills a small
hole in the flue for the wand, then later
patches it. The analyzer provides an
immediate reading. Our furnace had a
76.9 percent combustion efficiency.
not bad considering furnaces at least 15
years old are usually 55 to 68 percent
efficient and this unit is 27 years old
(typical lifespan is 15 to 20 years).
This test also measures:
• amount of carbon monoxide in the
flue gases
• draft pressure in the flue to determine
if gases could leak into the
house.
These are safety issues. If waste gases
aren't being drawn up the chimney,
moisture, carbon monoxide and other
pollutants could be flowing into your
home. Common causes of vent problems
(allowing gases to "backdraft" into the home) are birds’ nests in the vent
pipes or vents that have come apart.
Erik often finds these problems. He
notes one common clue: “If you have
moisture on your windows, the first
thing to check for is backdrafting in the
furnace and water heater flues.”
Erik tests for backdrafting in the
water heater flue as well by holding a
flame or a smoke stick next to the draft
diverter (Photo 2).
The check of the heating and hot water
systems concludes with a visual inspection.
Rust particles (called “scaling”)
inside the furnace heat exchanger indicate
corrosion, which will eventually lead to
holes and combustion gas leakage. Scaling
may also be visible on top of the water
heater around the draft diverter.
Erik looks to see if the furnace filter is
clean and installed correctly. “Clogged
filters can cause a moderate increase
in heating costs, but more significantly,
cause the heat exchanger to overheat
and fail, and cause the fan motor to
heat up, increase
electric consumption
and reduce
the life of the
motor.” He also
looks for combustibles
stored
near the furnace or
water heater,
because the flame
could cause an
explosion.
Other common
problems Erik has
found include disconnected flue pipes, leaky ductwork,
clogged condensation pipes, dirty
burners and dirty fan blades. “I’ve
found many furnaces missing the cover
for the filter slot, and major leaks in the
return-air ductwork. This causes
depressurization in the furnace room
and can draw dangerous exhaust gases
out of the flue pipe and distribute these
gases throughout the house,” he says.
Click Image to enlarge.
1. Furnace efficiency test: The auditor tests the furnace
exhaust with an electrical gas analyzer, which gives a
combustion efficiency reading. It also measures draft pressure
to determine if flue gases might leak into the house.
2. Backdraft test:
With all doors and
windows closed and
all combustion appliances
turned on, the
auditor tests for backdrafting
at a natural-draft
gas water heater.
The flame, held next
to the draft diverter,
should be drawn up
into the flue.
“Old boilers, originally
designed for coal, then converted
to oil and then to natural gas,
can be as low as 55 percent efficient—
that’s 45 percent waste!
The best furnace designs feature
variable-speed fan motors and
modulating or multi-stage burners,
which enable the furnace to
match its Btu output to the
home’s temperature
needs,
thereby
increasing
the system’s
efficiency.”
Testing for air leakage
Part two of the audit entails a “blower
door” test, which measures the home’s
“tightness,” or air infiltration rate. Erik
first closes all doors and windows, then
he sets an adjustable panel with a variable-
speed fan in a doorway, completely
sealing it. He turns on the fan to blow
air out of the house, which reduces the
indoor air pressure and then measures
airflow through the fan at predetermined
pressure points (Photos 3 and
4). Outside air then enters through
cracks and gaps in walls and ceilings.
With the fan running, you can feel air
come in with your hand, especially
around leaky windows and doors.
Gauges connected to the fan measure
the airflow rate needed to maintain a
constant pressure, allowing the auditor
to calculate the leakage rate.
Newer homes are built tighter under
the most recent Minnesota building
code. (Most other state codes have
tighter rules too.) It even requires
special ventilation fans to ensure
adequate fresh air. Still, their leakage
rate is often equivalent to a 6 x 6-in.
hole in a wall. Older homes weren’t
built nearly as tight. They often have a
leakage rate equivalent to a 19 x 19-in.
hole, which is like having a window
wide open all the time! The house we
tested had leaks totaling .77 sq. ft.
(about an 11 x 11-in. hole). Erik estimates
that sealing air leaks alone will
save 10 to 20 percent on this home’s
annual heating bills.
Erik pointed out several signs of air
leaks: stains around exhaust fans and
dirt on insulation. A batt of insulation
between joists in the basement was
dirty, meaning the insulation was serving
as a filter for air leaking in through
the foundation. “You can’t fix these
leaks with insulation because it won’t
stop the airflow,” Erik says. “You have to
seal them with caulk, expanding foam
or some other sealant.”
TIP
Have the audit performed in the
spring, summer or fall. Auditors are
usually busier in the winter, when
homeowners see a spike in energy
bills, and the wait for an audit can be two months or more.
Click Image to enlarge.
3. Blower door test: With all doors and windows closed,
the auditor inserts a blower door in the front or back
doorway and starts the fan.
Click Image to enlarge.
4. The gauge shows the pressure difference between the
inside and the outside and the airflow per minute. From
these, the auditor calculates the leakage rate.
“In my opinion,
there’s no limit to how tight you
can make the ceiling. The less air
that goes out the ceiling, the less
that will come in around doors,
windows and other leaky areas.
When you’re carrying water in a
bucket, it doesn’t matter if the top
leaks because no water is going
to get out. What
matters is the
bottom. Think
of your house
like an upsidedown
bucket
holding heat.”
Pinpointing sources of energy loss
While the blower door test measures
the overall leakiness of the house,
infrared scanning (technically called
“thermography”) graphically identifies
the precise locations of those leaks. Erik
keeps the blower door fan running to
draw in outside air. Then, using an
infrared camera, he scans the walls and
ceilings, photographing surface areas
that show up as cooler (Photo 5).
Cold areas show up as blue, and warm
areas as yellow (Photos 6 – 8). Today (a
chilly day in March), the framing members
showed up as blue, since they’re
cooler than the insulated portion of the
walls. (The opposite would be true on a
hot day when the indoors is air conditioned
and the outside air is warmer.)
Air leaks in the ceiling typically cause
the greatest energy losses. Openings
made for light fixtures, plumbing vents,
exhaust fans, attic access and smoke
alarms will leak if the builder doesn’t
make an extra effort to seal them. In
this house, the area around the attic
access panel and the exhaust fan in the
upstairs bathroom showed extensive
leaking (Photo 6), while a ceiling light
fixture, which must have been sealed
better, leaked very little.
Electrical outlets and light switches
on outside walls also usually leak, unless
the builder took extra pains to seal
them. The infrared scan showed that
four of these in the north kitchen wall
leaked profusely (Photo 7). The
homeowner confirmed this, noting
that she often felt cold drafts when
standing by this wall.
While some of these problems
are easy to fix — foam weatherstripping
on the attic access panel, spray
foam or caulk around the exhaust fans,
and foam seals under the outlet and
switch cover plates — others are difficult
to seal and may not be practical to go
after. Leaks around exterior wall top
plates and inadequate insulation in
some wall cavities are common (Photo
8) but hard to access and therefore
expensive to remedy.
Expect some air leakage around windows,
sliding patio doors and exterior
doors. “All doors will leak, especially since people step on the threshold as
they enter and leave the house, wearing
a gap between the door and sill,” Erik
explains. “The only doors that don’t leak
are the ones on submarines.”
Infrared scanning can identify other
hidden problems. It’ll show cold spots
where insulation is poor or missing.
Erik has even found double-pane windows
that have failed. Condensation
between the layers of glass, which is the
usual sign of failure, hadn’t shown up
yet. Yet the infrared image showed that
the centers of the panes were cooler
than the sides, which meant the special
argon gas they had been filled with was
completely gone.
Since infrared scanning works by
identifying heat differences, it can also
detect water leaks (not to mention
warm-blooded critters in the walls).
Erik once found an area in a basement
floor that was inordinately warm. Turns
out a hot water pipe was leaking under
the concrete, which explained the
homeowner’s high energy bill.
Click Image to enlarge.
5. Thermography: The auditor uses an infrared camera to scan walls and
ceilings. The camera detects temperature differences and can pinpoint cold
spots and air leaks.
Photos and infrared scans
Click Image to enlarge.
6. Dark blue areas around the perimeter of the
attic access panel indicate air leakage. The
overall blue tinge indicates poor insulation.
Click Image to enlarge.
7. Electrical outlets and switches typically
leak, but this is excessive. This kitchen wall
feels cold and drafty in the winter.
Click Image to enlarge.
8. Inadequate insulation in a wall cavity and
gaps in the top plates (wall framing) cause
most of the air leaks in this dining room.
Final report — what you can save
Once the testing is complete, the auditor prepares a comprehensive
report detailing the amount of leakage, ways to improve efficiency, the
cost of specific improvements and the time frame for recouping those
investments (see below).
The report lists specific low-cost steps for reducing energy that you can
usually do yourself. For this house, they include insulating the attic access
panel, weatherstripping it with closed-cell foam tape, sealing ceiling penetrations
at electrical fixtures, insulating kitchen soffits, adding attic
insulation, insulating the rim joists and caulking around windows,
doors and base trim. Erik estimates that these upgrades will cut annual
energy bills by 15 to 20 percent. Adding insulation to exterior walls isn’t
worth the cost.
The furnace, installed when the house was built in 1979, had an “annual
fuel utilization efficiency” of about 68 percent. This furnace is operating
well below the current minimum standard specified by the building code
and far below the efficiencies currently available. (Energy Star furnaces
must be at least 90 percent AFUE.) Erik recommends replacing any old furnace
(in Minnesota’s cold climate) that’s not at least 80 percent efficient
since newer models use less energy and eventually pay for themselves (in
this case, in nine years). Your energy auditor will make these calculations
and recommendations based on your local climate. Furnaces that are at
least 95 percent efficient may qualify for a federal tax credit.
Installing a programmable thermostat in this home will pay for itself in
just two to three years. A new high-efficiency air conditioner isn’t a priority,
but it’s likely to be a priority in warmer climates. You want to recoup
your investment through predicted energy savings within seven to 10 years.
Click Image to enlarge.
The final report lists energy efficient
upgrades, their cost (of hiring a contractor
or doing it yourself) and estimated annual
savings. Upgrades that pay back in seven to
10 years are considered good investments.
Recommended energy-saving tips
• Seal leaks in ductwork
• Clear space in front of heating
units, registers and radiators
• Reduce water usage by using
low-flow showerheads
• Insulate the water heater tank
and water pipes
• Wash clothes in cold or warm
water. Rinse with cold.
• Dry laundry loads consecutively
to maximize dryer efficiency
• Replace incandescent bulbs
with efficient compact
fluorescent bulbs
• Use timers or motion detectors
to turn off lights when not
needed
• Install air-sealing gaskets behind
switch/outlet cover plates
• Lock windows to create a
better seal
• Add weatherstripping and
caulking around doors and
windows
• Seal around pipes and ducts
that penetrate outer walls
