Making Old Windows Energy Efficient – Caulking and Weatherstripping

If you have evaluated your current windows and concluded that replacement is not necessary, you can improve the energy efficiency of your windows by reducing air leakage, heat loss and solar gain. Caulking and weatherstripping help to reduce air leakage that can occur through cracks within the window assembly and around the window frame. If properly applied, these air sealing techniques can be recovered in energy savings within a year.

Before attempting any air sealing, you need to assess your ventilation needs for indoor air quality and detect air leaks. A qualified technician can perform a blower door test. You can also detect air leaks yourself by:

• Shutting a window or door on a piece of paper and seeing if you can extract it without tearing
• Shining a flashlight at night over potential gaps and having another person check for light rays from the outside of the house

Caulk provides a flexible, effective seal for gaps, cracks and joints up to 1/4 inch wide. Common caulking compounds include butyl rubber, latex, silicone, oil or resin-based, water-based foam sealant and polyurethane in an expandable spray foam. Most come in disposable cartridges that fit in half-barrel caulking guns, but they can also be found in squeeze tubes and aerosol cans.

Remove old caulk and paint residue around the window before applying new caulk. It’s best to do this job during dry weather when the outdoor temperature is at least 45 degrees F to prevent cracks from swelling and to allow the caulk to set properly. Watch the process in this video:

Weatherstripping helps to repair air leaks around doors and window. To determine how much you will need, add the perimeters of the doors and windows that will be treated and then add 5-10% to allow for waste. Choose weatherstripping that will seal well when the door or window is closed while allowing it to open freely. Common types of weatherstripping include vinyl, metals, open-cell foams and felt. Learn more in this DIY installation video:

Weatherstripping applications should be done when the temperature is above 20 degrees F. Before doing any cutting, measure the area to be weatherstripped twice. Weatherstripping should be applied between the window sash and frame or to the entire door jamb with one continuous strip along each side of the door; it should compress when the window or door is shut.