Learn about Open-Cell Polyurethane Spray Foam Insulation

Spray foam insulation is sprayed as a thick liquid into cavities and other spaces, where it sticks and expands, forming a network of cells (bubbles). Open-cell spray foam is more permeable to humidity than closed-cell spray foam, and has a lower insulating value, typically about R3.5 per inch.

Spray foam insulation must be mixed and installed correctly at your home, by a trained technician. In a very small number of cases, incorrect application of spray foam has sometimes resulted in ongoing fumes and smells for the homeowner, when the foam failed to cure properly. Check for references from customers when you are choosing a spray foam insulation company. Also be aware that you should stay away from your home during spraying and for about two days after while the foam cures. The exception is small spray foam jobs, for small cracks around sills, window openings, etc., that can be done yourself, carefully, with spray foam cans available at hardware stores.

Spray foam can save a lot on your heating bill, especially when applied throughout the walls, attic, and basement of an older, less airtight home. It insulates and seals drafty air leaks at the same time, by filling in cracks and holes in your building envelope. Open-cell spray foam typically uses water or carbon dioxide as a blowing agent, less harmful to the Earth's climate than the HFC blowing agents that are still being used (and gradually being phased out) in closed-cell spray foam.

Spray foam was invented in the 1940s, but could only start to be sprayed in homes in the 1950s, with the invention of the Blendometer by Walter Baughman. This handy machine could mix the two components of spray foam together on-site, which then react together to make the foam.