Gaps around windows sashes and frames are responsible for a significant amount of heat loss; even small gaps can be big energy wasters. To find out if your windows have gaps, hold a piece of tissue paper or plastic wrap near the window on a windy day and move it around. Wherever you see movement (either outward or inward), there’s a significant leak. If you have drafty windows, follow our step-by-step instructions to learn how to weather-seal windows to conserve energy and save money.

Before you begin, make any needed repairs to the window and its frame. Once complete, the first step to weather-seal windows is to caulk, especially on the exterior. Also, check that the glazing putty on the outside is free of gaps and seals tightly against the window. Where glazing is failing, scrape it out and apply new glazing. On the inside, see that the joint between the glass and the sash is sealed with a flexible, paintable latex caulk before being painted.

Weather-stripping where two surfaces push together (the horizontals of a double-hung window and the verticals of a casement or sliding window) is straightforward. Where two surfaces slide against each other (the verticals of a double-hung window and the horizontals of a casement or slider) calls for more precision. However, most weather-stripping applications only take an hour or two to apply. We’ll show you how to do both with our guide to weather-stripping windows.

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