Use a Candle to Find Mystery Air Leaks in Your House

With temperatures around the country plummeting over the past few days, any air leaks in your home have likely become particularly noticeable. Perhaps you knew these cracks and crevices were there, but hadn’t gotten around to dealing with them yet. Or maybe, you did take the time to properly seal your home, and thought you took care of all the leaks, but the steady stream of frigid air coming from your wall says otherwise.

This seems like it should be straightforward enough: Find the additional leaks, and then seal them up. But sometimes, no matter how hard you try, you just can’t locate the leak. Here’s what to do if you run into that problem.

How to use a candle to locate air leaks in your home

One way to find a mystery air leak in your home is to use a candle. Here’s what to do:

Find the right candle

Generally speaking, longer, thinner candles—like the ones you’d put in candlesticks, or use at a candlelight vigil—work better than candles that come in glass jars. That’s because you’ll need the flame to be out in the open and accessible.

Some experts, including those at the U.S. Department of Energy (DOE), suggest lighting a stick of incense instead of using a candle for this task. While it’ll certainly get the job done, it’ll also make your home smell like incense (which not everyone is on board with).

Turn off any sources of blowing air

This air-leak-locating method is much more effective if there’s not any type of blowing air coming from fans, or forced-air heating systems. Switching off any fans should be pretty easy, but if you don’t want to switch off your furnace, at least wait until it’s not actively blowing air through the vents. (Or close or temporarily block the vents.)

Go through your home

Now, light your candle, and get to work. Starting with the wall, floor, or general area where you’ve felt the air leak, slowly—and extremely carefully—move the candle around the room, paying close attention any time you pass over or near areas prone to air leaks, like windows, doors, baseboards, and switch plates.

If the flame begins to flicker—or extinguishes completely—in a certain area, you’ve probably found your leak. But just to be sure, hold the lit candle completely still near that same spot to see if the flame flickers or goes out again. (In case the first time, it happened because you were moving the candle around.)