Caulk and Seal Leaky Windows

Save big by caulking or covering drafty windows.

You're probably already aware if you have drafty windows, especially if you sit or sleep near one. Leaky windows are expensive and make your house uncomfortable.

There are a number of ways to test for leaky windows (and doors as well). It's best to check on a windy day or when there is a large difference between the inside and outside temperature. It's difficult to detect drafts if the temperature inside and outside is close or there's no wind. Winter is usually the best time to check. My favorite tests are the wet hand test, plastic wrap on a pencil, and smoke from incense.

Testing for Leaky Windows

The first test is to see if you can feel the draft on your hand. (A little water on your hand makes this more effective.) Make sure the furnace and any fans aren't on during the test. If you feel a draft you've got a leaky window.

Taping a piece of plastic wrap on a pencil and holding it next to the window is an easy way to see if there is a draft. Be sure the plastic wrap isn't touching anything and can move freely. Again, make sure the furnace fan isn't blowing while you're testing.

The most dramatic test is to use smoke from a stick of incense. (Some suggest using a candle, but that's dangerous and there's a good chance you'll catch your curtains on fire and burn your house down.) Incense is cheap and effective.

Smoke Rising Away from Leaky Window Smoke Rising by a Leaky Window
Smoke Rising in Center of Room Smoke Rising by a Leaky Window

Note the difference between how the smoke rises in straight lines away from the window, but near the leaky window the draft is strong enough to disturb the smoke. Fixing this window will save a lot of energy and make the room more comfortable.

It might be a good idea to check all your windows (and doors) at one time while you have everything out. Make a list as you go to help decide which to fix first.

Fixing the Drafty Windows

Prioritize and fix windows that leak the most and those that you spend time near. There are a variety of options to stop the drafts. We'll start with the easiest first.

Each option has pros and cons.

  • Window plastic is the cheapest and easiest but most people take it down in the spring, so it won't help you in the summer.
  • Temporary caulk might be a solution. You still can't open the window without removing the temporary caulk. It also has a strong chemical smell, so think twice about using it in your home. Consider using rope caulk instead.
  • Permanent caulking is a bit more work but you only have to do it once. However, if your windows leak in a place you can't caulk, you've got a problem.
  • Replacing windows is very expensive but if you install good windows you don't have to worry about it again.

See more things you can do around your home.