A Division of Apple Hill Woodworks, Inc.                 Serving Massachusetts & Southern NH

Types of Foam

Spray polyurethane foam is available in many different formulations. The two main types of spray foam used for building envelope insulation are open cell foam (also referred to as 1/2 lb foam or low density foam) and 2lb closed cell foam. Both types of foam offer excellent thermal insulation and air sealing properties. At FoamRun, we analyze the needs of your building to determine the best type and amount of foam needed for your project.

Open Cell

Open cell spray foam offers R-Values of 3.5 to 3.8 per inch of thickness. Open cell foam is often referred to as 1/2 pound foam, because the final product weighs 0.4 to 0.6 pounds per cubic foot. Open cell foam uses water as the blowing agent. The blowing agent creates the millions of tiny cells you see in the foam. As the foam cures these cells actually crack open and become filled with air to give the product its insulating properties. Open cell foam is sprayed as a liquid and expands up to 120 times its volume to fill every nook and cranny. This expansion creates the air tight seal of the building envelope that only spray polyurethane foam can provide.

2lb Closed Cell Foam

2 pound closed cell foam delivers R-Values of 6.0 to 7.0 per inch. The cured 2lb spray foam has a weight of 1.5 and 2.0 pounds per cubic foot and is also sprayed as a liquid. The expansion rate of 2 pound foam is about 35 to 50 times its liquid volume. Closed cell foam derives its name because of the structure of the cells in the final foam. The closed cell foam used by FoamRun uses a non-ozone depleting HFC-245fa blowing agent. When fully cured, the millions of tiny cells remain closed and intact and trap the reacted gases to deliver these ultra high R-Values. Closed cell foam at thicknesses greater than 2 inches also provide vapor retarding capabilities since the perm rating at his minimum thickness is less than 1.0. 2 pound closed cell foam is very strong. In fact, tests have shown that the racking strength of a wall with closed cell spray foam can be increased by up to 300%.


Please check the articles listed in the sidebar to learn more about the differences between open cell and closed cell spray foams.

FOAM RUN — Serving MA and Southern NH — (978) 386-7737