What is Spray Foam Insulation?

by Erik North on May 4, 2011

What is spray foam insulation


Have you heard of spray foam insulation? What is it? What are the different types of spray foam? What is spray foam insulation currently used for?


For the homeowner who is researching alternatives to fiberglass, there is spray foam. Instead of the scratchy arms and skin irritation of fiberglass or rock wool, you can enjoy the mess, expense and if you’re very lucky, the buckling of an overfilled wall cavity or window box. Congratulations…it’s your chance to enjoy an entirely different set of household problems.

Spray foam insulation is a two part polyurethane application that when combined forms a solid foam insulation for use in the home’s building shell. Spray foam is one of the most versatile forms of insulation available. It can seal your home from air and moisture intrusion, strengthen building structure and provide thermal, air and vapor barriers capable of ably performing in all U.S. climates.

There are many different types of spray foam that fall into two categories: Open Cell and Closed Cell foam. Open cell is foam where the tiny cells of the foam are not completely closed. They are broken and air fills all of the open space of the foam. This causes open cell foam’s spongy feel.

With closed cell foam, its tiny foam cells are closed. Logical enough. They are filled with a gas and packed together, causing a greater density and higher insulating value. Open cell foam typically weighs 0.5 lbs./cu. ft. compared to 2.0 lbs/ cu ft for closed cell.

Sprayed closed cell foam has an aged R-value of approximately 6.0 per 1 inch thickness (varies depending on the particular formulation). Open cell foam has an aged R-value of around 3.5 per inch.


Modern spray foam insulation has been used since the 70s oil shocks but spray foam actually has its roots with the advent of polyurethane foam in the 40s.

Originally, polyurethane supported the effort in World War II, used by the military to produce plastics for ships and airplanes. It was the invention of the ‘Blendometer’ by Walter Baughman (and it will surprise you not one jot that the ‘Blendometer’ was invented in the 50s) that allowed combining the various plastic polymers into a foam. The first machine for spraying foam as an insulation was built in 1963.

Current Uses

Both open and closed cell foams are mainstays in modern home and commercial construction. Both types of spray foam insulation are used in attics and wall cavities while closed cell as a vapor impermeable barrier can be used in sub-grade (you know, the basement) applications. They also provide excellent sound proofing. Spray foam insulation will adhere superbly to any clean surface, allowing it to be applied directly to walls and ceilings.

There are advantages and disadvantages to consider. Spray foam insulation is generally more expensive than either cellulose, rockwool or fiberglass. Closed cell spray foam also has a higher R-value than any fibrous insulation and as a solid foam insulation resists wind washing and air infiltration. The vapor impermeable quality of closed cell insulation make it ideal for high moisture environments such as your typical New England basement.

Though do it yourself kits are becoming more common, spray foam’s high learning curve for weekend warriors leaves spray foam largely in the province of professional contractors. As alluded to earlier, because spray foam can expand aggressively it has been known to buckle drywall and window and door frames.

Finally, the most challenging aspect of spray foam is moisture control and the building shell. Because spray foams create an air barrier (and closed cell creates a vapor barrier), the possibilities exist to trap moisture and damage framing elements (dry rot, mold, shingle damage).

Every climate zone in the US has different requirements to control moisture and humidity. When considering spray foam, homeowners would be wise to consult with an experienced energy auditor or engineer.

{ 2 comments… read them below or add one }

ADITYA May 12, 2011 at 11:29 am

Good Info site for Energy related activities


Mark June 21, 2013 at 6:02 am

Great information you have shared in this post, your point is right that spray foam is one of the most versatile forms of insulation available and it can seal home from air and moisture intrusion, strengthen building structure and provide thermal, air and vapor barriers capable of ably performing in all U.S. climates. Nice to know this information, thanks for sharing his great post..


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