How Much Spray Foam Should You Use Around Windows?

Safety First

• Spray foams contain chemicals that you should protect yourself from breathing in, especially if you have asthma or other related breathing issues. Review the label on your chosen spray foam, and follow safety instructions. Wear old, long-sleeved clothing to avoid contact with the skin, though skin contact does not often do harm in these products. If you have asthma or breathing issues, wear a mask to keep from breathing chemical products, and always protect your eyes with safety glasses. Pay attention to the cure time on the product label, and avoid staying in the area around that window until the product has had time to cure.

Don't Over-Fill

• Spray foams are designed to expand and contract with the area filled. Over-filling with spray foam could bow the joints of the windows, making it difficult or impossible to use the window properly. Choose a foam that has a good applicator tip, and fill only about 50 percent of the gap with spray foam, as it will expand more to fit the area. While most spray foams don't drip, put a precautionary drop cloth under the area you're spraying because the foam can permanently damage carpet or wood floors.

Check for Overflow

• It may be difficult to control the amount of foam coming from the applicator tip, so spray your first applications in areas that are more inconspicuous. Move slowly and watch that you don't overflow the area. If you do, wait until the foam hardens and you can easily shave the overflow down with a razor or sharp knife.

Check for Drafts

• If there is no draft coming through the joints of the window, there should be no need for spray foam. Test for drafts by simply feeling the air flow around window joints, or by using a lit candle. Move the candle slowly around the window frame, and watch the flame. If it flickers, use spray foam to fill the drafty space. Only fill the space half way because the foam will expand and contract to fit the space.