Because windows may let in more than the view outdoors, window sealants are important in all seasons. About one-quarter of the heat loss from a house in winter is due to air leakage around windows and doors. In summer, conversely, these cracks also allow unwanted heat to seep into the house and burden your air-conditioning system.

As years pass, sealant around window panes and the larger window frame may dry up and deteriorate, particularly in existing houses that have windows that have been sealed by common putty. Aging, shrinking sealants may allow air infiltration around individual window panes, as well as the large frame of the window structure.  Today’s improved window sealants include the following options.

Silicone and Polyurethane Caulk

100% silicone caulk is the leader in many household air-sealant applications. Silicone fills cracks and gaps and remains viable for up to 20 years without drying out and shrinking. It also inhibits mold and mildew growth, effectively prevents water seepage, and even keeps insects out. Silicone is transparent and neutral to the color of window components. Applied in temperatures above 40 degrees, silicone is water-resistant after only about 30 minutes of drying time.

Unlike silicone, polyurethane caulk is actually an organic compound and typically applied only to the exterior of window components. Also, unlike silicone, polyurethane caulk can be painted. However, although polyurethane is somewhat more resistant to the deteriorating effects of UV sunlight than silicone, it is generally not as durable as silicone and may harden and become brittle in cold weather.

Window Sealants for Bigger Jobs

To fill larger gaps and openings around the main window frame, polyurethane foam in a can is a convenient and effective space filler.  As it seals more effectively than most insulating materials, foam also helps reduce heating and air-conditioning loss around window frames.  Once it cures completely, foam can readily be shaped and trimmed, as well as painted. 

The professionals at Mowery Heating, Cooling and Plumbing have more information about window sealants that help maintain indoor temperatures in all seasons.