Detecting Air Leakage in Your Home

What You'll Need
Bath towel
Kindling piece

In most homes, even some of the newer ones, you're almost certain to find some air leakage. By investigating, you will find air leaking through small openings you didn't know existed. In moderate climates, this leakage may not be a big cost factor or environmental factor. But in climates where outside temperatures can vary even 20 degrees from your in-house temperatures, it will probably be to your advantage to find these leaks. Unless you have strong breezes blowing through your house, you may find that fixing these leaks is more simple than finding them. Here's how you can find air leaks in your home:

Step 1 – Check for Window Leaks

A common place where you can usually find air leaks is around windows separating the room you are in from the outdoors. You can usually detect these leaks by observing the small flame of a candle held near the window. If you see the flame flicker, this will usually indicate there is an air leak. However, the movement of the candle flame could also be from air circulating from a HVAC vent. Place a folded bath towel along the bottom edge of your window to block any flow of air. Then, hold the lighted candle near this part of the window again. If you see no movement of the candle flame, this will be further evidence that your window is leaking air.

Step 2 – Check for Door Leaks

The most frequently found leaks at doors usually come from the crack between the bottom edge of the door and the doorstep. Check for these leaks at night, during darkness. Shut off any light in the room. Have a helper turn on a flashlight, go outside, shut the door, and hold the flashlight beam at the bottom edge of the door, pointed toward you. If you see light from the flashlight under the door, you'll know there is a gap through which air can leak. You can also use this method to check the side cracks and top crack of the door.

Step 3 – Check Dryer Vents

Dryer vents are often a source of leaking air. If the air outside your home is a different temperature than that inside, the air will usually be leaking through the vent. Test the air in the dryer when the dryer has been shut off for awhile. If air in the dryer feels cooler when the outside air is colder than home air, or if you feel a draft in the dryer, it is likely evidence that your vent is leaking air.

Step 4 – Check Your Fireplace

Another common source of air leakage is a fireplace. In winter months when there is air flowing through your damper, heavier cold air will flow into your fireplace, while lighter, warm air will flow up the chimney. To detect this air movement, light a small piece of kindling on fire. When it begins burning, douse the flame and hold the kindling in the fireplace. If air is leaking up the chimney, smoke from your kindling will quickly rise up the chimney with the rising air.