Spray Foam Insulation: Closed-Cell vs. Open-Cell
What’s the Difference – Open Cell and Closed Cell Foams
The importance of distinguishing between the two types of spray polyurethane foam cannot be understated. When it comes time to insulate a home or commercial building, you must opt for open-cell foam or closed-cell foam, or a specific combination thereof. Each type of foam distinctly impacts project costs, application methods, and building performance. There are two major factors distinguishing closed-cell and open-cell foams: structure and density.
The structure of open-cell foam consists of tiny bubbles or cells that aren’t fully encapsulated–they are broken, torn, ripped, etc. Because they’re broken, air fills the open space inside the bubble, which results in a soft, spongy material.
Closed-cell foam differs in that every bubble or cell that makes up the foam is completely encapsulated and packed tightly together. The bubbles aren’t filled with air, but rather a gas that aids foam expansion and insulation properties. This results in an altogether harder, stronger material than open-cell foam.
The blowing agent, which aids in forming the bubbles or cells that make up SPF’s foam structure, is usually water for open-cell and high-R-value chemicals for closed-cell.
Closed-Cell vs. Open-Cell Material Density
Closed-cell foam is roughly four times as dense as open-cell for insulation applications. To ascertain foam density, one cubic foot (cu. ft.) of foam material is weighed. Open-cell tends to be roughly 0.5 lb./cu. ft. in density, whereas closed-cell ranges from 1.7 to 3.0 lb./cu. ft. in density, or even higher for certain applications. (Note: these density figures are rough averages. Every SPF product will differ based on its formulation.)
R-value is a way to denote a material’s insulating properties, and the higher the number per unit thickness, the better the insulation value. Closed-cell spray foam has an R-value of about 6.0 per inch (R-6), while open-cell SPF comes in at roughly R-3.5. (Note: these R-values are rough averages. Every SPF product will differ based on its formulation.)