What Causes Drafty Windows?

And What Can Be Done about it

With winter coming you may be wondering what caused all those drafts last year and what can you do to prevent them this year.

Since, air can’t penetrate glass, something else must be causing your drafty windows. The first thing to check is whether the window is tightly latched . Windows are designed to be latched, rather than just closed. Latching them forces the seals around the window to actually seal. You’ll be amazed at how much difference this one little thing makes. Worse yet, I’ve seen where the windows weren’t even closed all the way leaving a 1/4 inch gap. This is especially true for “double-hung” windows. If they aren’t latched, vibrations can cause the upper window to slowly creep downward.

Thermopane Windows

If your windows are latched, and you have thermopane windows, i.e., double-glazed windows… the problem is typically air leaks around the window frame.

This can be the result of poor insulation in the spaces between the window frame and the studs or simply deteriorating caulk around the outside of the window.

Caulk is a cheap and easy fix. You can get a tube of caulk for a few dollars and a caulk gun for a few dollars more. And go around your house looking for any crack or hole you can find.

I recommend spending a couple of dollars more and getting a good caulk gun like this with the smooth rod rather than the cheaper one with the notched rod. (It makes the job much easier!)

The smooth rod gives you much more control.

If you have single-pane glass rather than double-pane glass your problem could be convection rather than actual leaks. Glass is not a very good insulator, so the glass gets cold and when the warm room air bumps against it, the air cools down. As it cools it slides down the wall and new warm air takes its place.

This creates a cold draft near the window and across the floor. This can be reduced by:

Getting new insulated (thermopane) windows.
Putting up heavy insulating drapes or shades.
Adding “storm windows”
Other Window insulating methods.

Use Bubble Wrap to Insulate Windows

Seal Around Windows with Spray Foam.

(You have to remove the moldings)

Apply Plastic Film

You can either apply it directly to the window frame or create wooden frames that can be removed easily in the summer.

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Thermopane Windows

Seal Around Windows with Spray Foam.

Apply Plastic Film

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