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Repairing or Improving
Existing Windows or Doors

Replacing Weatherstripping

The gaskets in a window should be flexible and durable, so that there is an airtight seal between the operating sash and the window sill and frame. An airtight seal is also needed between a door and its frame. The airtightness of the joint between operable sashes and a window frame or between a door and its frame depends on the type of weatherstripping used and the amount of pressure that can be applied on the joint. Instead of sliding seals with brush-type weatherstripping, it is better to use compression seals, which can be squeezed tightly between the moving sash and the window sill and frame. They are resilient over many years and are not subject to cracking or other deterioration.

You may not be able to avoid brush-type seals, especially if you are selecting horizontal sliders. On a horizontal-slider type of window, look for thick brush seals with a thin, flexible plastic flange embedded in the brush to minimize air leakage.

Weatherstripping is used to prevent air leakage at the parts of an operable window that move. It is usually a simple task to replace worn weatherstripping or to install additional weatherstripping if required. Good quality weatherstripping costs more but will pay for itself by performing better and lasting longer. Check with knowledgeable salespeople when selecting weatherstripping.

For older wood-frame windows, look for good quality, self-adhesive plastic V-strip weatherstripping. This product can be installed in very small spaces, works in sliding and hinged applications, and can often be installed without removing any part of the window. Hinged windows usually require a combination of V-strip and compression-type weatherstripping. Follow the manufacturer's instructions when installing either of these products.

Where to Weatherstrip a Single-Hung Window

Many older houses have single-hung windows that have one fixed sash and one operable sash. With this type of window, weatherstrip the side of the sash and the meeting point of the upper and lower sashes.

Weather Stripping

Brush Weatherstripping on a Sliding Window

To replace brush weatherstripping on a sliding window, remove the sash and pull the old weatherstripping out of its slot. Cut the new weatherstripping to the length required, and snap or slide it into the slot. Tack or staple the ends of the brush to ensure that it stays in place before you re-install the sash.