Home Energy Audits FAQ's
Q: What is Home Performance Contracting
Q: What is "infiltration"?
Q: What is the Blower Door Infiltration Test?
Q: Why perform a blower door test?
Q: What do I need to know about the Blower door test?
Q: What exactly is measured?
Q: Where do you usually find the biggest air leaks?
Q: How much reduction can I expect?
Q: Is "air sealing" the same as "insulating"?
Q: I am considering a new heating or air conditioning system. Will these upgrades be affected?
Q: Don't air leaks keep the indoor air fresh?
Q: What about bathroom and kitchen smells when the house gets airtight? Leaks help with those, right?
Q: I already have bath and kitchen fans - aren't they good enough?
Q: What about dampness in the bathroom when the house gets tighter?
Q: What Is Home Performance Contracting?
A: Home Performance Contracting is a new integrated method for analyzing a home's issues and performing improvements. The Energy Star Program of the US Department of Energy is promoting this integrated approach to improve the energy efficiency in existing American homes.
The many components of your home must be properly designed, installed, and maintained to perform their functions effectively and efficiently. Often contractors focus only on their own field of expertise, like HVAC or insulation, with little or no thought as to how the components interact.
In contrast, home performance contractors, take a whole-house approach that reveals the real issues and provides comprehensive improvement solutions. This cost-effective method saves the homeowner money while improving both the comfort and health of the home.
Q: What is "infiltration"?
A: "Infiltration" refers to the air that flows into our houses. Houses (and all buildings) "breathe" as air flows in and out of them. This breathing helps to keep indoor air fresh.
But most houses leak too much and in ways that degrade rather than improve indoor air quality. A house can act like a chimney, sucking cool air in at the bottom to replace the warm air flowing out the attic. This reverses when the house is cooled. Winds blow through the house horizontally adding to this chimney effect. In order to stay comfortable, we constantly pay to recondition, either heat or cool, this new air infiltrating into our homes. A leaky house with a high infiltration rate feels uncomfortably drafty, and costs significantly more to condition.
Q: What is the Blower Door Infiltration Test?
A: This test measures and locates the sources of air infiltration - the air leaks. The Blower Door test is like a 20 mph wind blowing on all sides of the house. A large fan is sealed into an outside door opening and calibrated to the size of the house. The fan blows air out of the house causing replacement air to stream in through all the leaks, both large and small, making them easy to spot. The resulting leaks are measured and identified. They are often easy to fix.
Q: Why perform a blower door test?
A:Leaking air costs money. Replacement air must be conditioned to be comfortable, and then it leaks out again. The only winner is the utility company.
Typically, American homes loose about 1/3 of their heated and cooled air to leaks. These air leaks make homes drafty and distribute dust and allergens to living spaces. Energy lost to infiltration is an environmental drain. Reducing this loss is an easy way to reduce global warming.
Contrary to popular perception, windows - even old windows - that are reasonably well maintained, usually account for only a small portion of these leaks. A Blower Door Test identifies the big leaks, and fixing biggest ones usually yields big rewards. Drafts are stopped so comfort improves; dust is reduced so cleaning becomes easier; allergens are reduced so asthma and allergy sufferers find relief; and energy use drops lowering monthly bills.
Q: What do I need to know about the Blower door test?
A: The blower door test is not dangerous. Everyone can remain in the house during the test. The furnace and all air conditioning must be shut off during test, so the temperature may change as a result.
There can be no fires in fireplaces, and ashes must be removed or covered if cold. Dampers must be closed to avoid sucking ash into house. Doors and windows should be closed and sealed, including any storm windows.
We will hunt in all rooms, including the attic and basement, looking for leaks.
Q: What exactly is measured?
A: We measure the total area of all leaks - the Effective Leak Area (EFA) in square feet. A typical existing home might have 1 to 10 square feet of leakage.
We measure the Air Change per Hour (ACH) rate @50 pascals and convert this to an ACH rate at normal conditions. The ACH rate is useful when sizing heating and AC systems. In new construction, the target for a well-sealed home is 0.35 ACH. Existing homes range from 0.50 ACH to 4.0 ACH in natural conditions. Air Sealing can reduce rates by 10% to 50%.
Specific leaks can be detected simply by feeling with the hand or visually with a non-toxic smoke puffer. The Home Energy Report lists the largest leaks that are found. We also report smaller leaks if they are found in large numbers.
Q: Where do you usually find the biggest air leaks?
A: The biggest leaks are often found in
- Basement band joists – where wood meets masonry
- Sump pump wells
- Basement walls with no additional finishes
- Poorly sealed ducts in basements and attics
- Attached garages
- Kitchen and bath plumbing pipes
- Unit air conditioners in window and wall openings
- Large holes in attic floor around chimneys, piping and wiring
- Recessed light fixtures in insulated ceilings
- Attic pull-down stairs
- Attic knee walls
Fixing smaller leaks, such as at receptacles and switch plates in exterior walls and cracks at the baseboards, doors and window casings, also produces beneficial results.
Q: How much reduction can I expect?
A: The specific reduction varies widely from house to house. A 10% reduction is usually easy to obtain. Some houses can achieve 30%, or even a 60% reduction. There are some houses with leaks which are widespread and elusive, so results can vary greatly. However, some leak reduction is always possible.
Q: Is "air sealing" the same as "insulating"?
A: No. Many insulation materials allow air to pass freely. Fiberglass for example is used as an air filter. If you are upgrading insulation, it is better to air seal first. This allows the sealer to see and plug more leaks before they are covered with new insulation.
Q: I am considering a new heating or air conditioning system. Will these upgrades be affected?
A: You should seal and insulate FIRST to reduce your heating and cooling loads. Then your new mechanical systems can be downsized. Ask your contractor to account for your shell upgrades when sizing your new equipment. With a smaller system, you can afford more efficient equipment. Properly sized, the system will operate at its highest efficiency and dramatically save even more in utility costs. If the reduced envelope load is disregarded when sizing new equipment, the system will cycle on and off more frequently, wasting energy in spite of your sealing efforts. You can check your contractor's equipment sizing by asking to review the "Manual J" calculation.
Q: Don't air leaks keep the indoor air fresh?
A: The "healthiest" air leaks are through windows and doors - fresh air washed by daylight. Typically, large leaks are from attics, concealed stud and floor joists, pipe and wire chases, and from under basement slabs - all dirty places. Therefore, these leaks bring in dirty air, which is often tainted with allergens and other pollutants.
Q: What about bathroom and kitchen smells when the house gets airtight? Leaks help with those, right?
A: A leaky window in a kitchen or a bath does not necessarily mean the smells are exhausted out of the house. Often smells are diluted into the house. Leaky houses can actually build-up unique aromas over time. Then, many homeowners resort to a variety of chemically based air fresheners which in-turn decrease indoor air quality and compound the leaky house smells. Older, leaky houses can contain strong musty odors and reminders of former occupants.
Q: I already have bath and kitchen fans - aren't they good enough?
A: Most of the bath and kitchen vents in American homes do not function well for exhausting bad air. They are loud, so users frequently do not use them. Or, they do not pull out air as intended due to poor installation, blockage or age.
Upgrading to the current generation of air change systems is an extremely effective way to improve indoor air quality. They draw little electricity and can run continuously at a low speed to keep bathrooms dry and mold free. Motion sensors respond to users automatically and quietly speed-up as needed to clear the air and excess moisture, before returning to low speed.
Q: What about dampness in the bathroom when the house gets tighter?
A: Leaky houses do not necessarily have dry bathrooms. It is common to find toilet and mildew smells, as well as scummy black seams that form in the tile joints and crevices when baths stay moist.
The new generation of exhaust fans can respond to the users as needed to dry out the bathrooms and eliminate black scum and mildew.
