Detecting Air Leaks
How to identify the source of drafts in your home.
There are a number of ways you can detect air leaks in your home, whether they're around windows, doors, attic hatches, or pipes and wires. These work best on a cold and windy day. That doesn't mean you can't test for leaks in summer—it's just a bit more work.
A few things to keep in mind before testing for air leaks.
- Turn off fans, furnace, or air conditioning.
- Take a roll of rope caulk and see if you can fix the leaks as you go.
- A combination of the techniques below should identify most air leaks. Incense seems to be the easiest and most effective of them all.
Technique | Description | How Effective |
Wet Hand | Simply dampen your hand and hold it near where you suspect air is leaking. If cold air is coming in you'll feel it. | Works well when cold air is entering the house; not as well if air is escaping. |
Look For the Light | At night have someone shine a light around the suspected air leak from outside. If you can see the light coming through, you've found your problem. | Very effective for walls and around pipes entering the house. Not as useful for windows. |
Incense | Hold smoldering incense near the area of concern. Watch the motion of the smoke. Use a small flashlight to make the smoke easier to see.
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Effective and can help find air entering or exiting the house. Tough to see against white backgrounds (you can put a piece of black paper off to one side for contrast).
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Plastic Wrap | Tape a one-inch-wide strip of thin plastic wrap to a pencil. Hold in front of suspected air leak. Several strips of Christmas tree tinsel also work well. | Not as sensitive as incense but useful for detecting many drafts, especially on windy days. |
Candle | Don't do it. You'll burn your house down. | Again, curtains on fire and such. |
Baby Powder | Shake the baby powder container and puff a bit of powder in the air. Watch to see the movement of the powder. | Not quite as good as incense but still effective. It takes some practice to get the powder to puff out evenly. |
Thread | For bigger leaks, you can tape a small piece of thread near where you suspect the leak and watch for moment. It won't be as dramatic as incense smoke. | Okay for bigger leaks or on a windy day. |
Blower Test (do–it-yourself) | Close all windows and doors. Turn on all exhaust fans. Put a window fan in a window blowing air out of the house. Use one of the techniques above to see where air is entering the house. | Works reasonably well to identify air leaks. Combine with the techniques listed above to find the leaks. Can be used in summer. |
Blower Test (professional) | It's the same idea as you doing the blower test but they have a bigger fan that fits, airtight, onto your front door. This provides a stronger pull and leaks are easier to see. | It's not a bad idea to try to deal with the major leaks yourself before having a professional blower test done. |
Probably the best approach is to identify and fix the biggest air leaks using the wet hand technique or incense/baby powder. After you've done that, a do-it-yourself blower test will be more effective at finding the remaining leaks. If you still believe there to be a problem you can have a professional blower test done.