Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly air sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment.
It is unwise to rely on air leakage for ventilation because it can't be controlled. During cold or windy weather, too much air may enter the house. When it's warmer and less windy, not enough air may enter. Air infiltration also can contribute to problems with moisture control. Moldy and dusty air can enter a leaky house through such areas as attics or foundations. This air in the house could cause health problems.
The recommended strategy in both new and old homes is to reduce air leakage as much as possible and to provide controlled ventilation as needed.
Detecting Air Leaks
You may already know where some air leakage occurs in your home, such as an under-the-door draft, but you'll need to find the less obvious gaps to properly air seal your home.
For a thorough and accurate measurement of air leakage in your home, hire a qualified technician to conduct an energy audit, particularly a blower door test. A blower door test, which depressurizes a home, can reveal the location of many leaks. A complete energy audit will also help determine areas in your home that need more insulation.
Without a blower door test, there are ways to find some air leaks yourself. First, look at areas where different materials meet, such as between brick and wood siding, between foundation and walls, and between the chimney and siding.
Inspect for any cracks and gaps that could cause air leaks:
Door and window frames
Mail chutes
Electrical and gas service entrance
Cable TV and phone lines
Outdoor water faucets
Where dryer vents pass through walls
Bricks, siding, stucco, and foundation
Air conditioners
Vents and fans.
You can also try these steps to depressurize your home to help detect leaks:
Turn off your furnace on a cool, very windy day.
Shut all windows and doors
Turn on all exhaust fans that blow air outside, such as bathroom fans or stove vents
Light an incense stick and pass it around the edges of common leak sites. Wherever the smoke is sucked out of or blown into the room, there's a draft.
If you don't want to turn off your furnace, you can just turn on all your exhaust fans to depressurize your home.
