Open Cell vs. Closed Cell

Posted by Amber Christopher April 23, 2015

Fomo Products, Inc. manufactures low pressure spray polyurethane foams of two general types: open cell or closed cell.  Choice of either foam type depends on the application requirements or desired outcome.

Generally speaking, closed cell foams consist of trapped gas bubbles formed during the foam’s expansion and cure. These gas bubbles consist of the blowing agent and are permanently locked into place during the curing of the foam. The trapped gas increases the insulation capability of the cured foam. The cured foam must be strong and of a medium density in order to lock in the gas bubbles. The foam’s strength, coupled with its closed cell nature, enable it to resist liquid water and function as a vapor retarder.

Open cell foams; however, are quite different in nature. The blowing agent gas is not trapped by the forming cells and instead is released to the atmosphere during foam expansion and curing. The foam cells have “holes” in their walls, enabling them to interlock and interconnect. The spaces within the cells are filled with atmospheric air, much like a sponge. Due to its porous nature, open cell foam does not resist liquid water or water vapor (humidity). Without trapped gas bubbles, open cell foams also do not need to be as strong, and therefore, are less dense than closed cell foams.

Attributes Closed Cell Foam Open Cell Foam
Typical Handi-brand® Aged R-Value at 1" 6.0 4.3
Superior Compression Strength x  
Liquid Water Resistance x  
Air Barrier x x
Sound Absorption x x (superior)
Vapor Retarder x  
Appearance Semi-rigid Soft, spongy
Increases Structural Strength x  
Interior Use x x
Exterior Use x  
Resistance to Mold x x
Commonly Called Medium Density,
2 pound foam
Low Density,
1/2 pound foam

Fomo Products, Inc. assumes no liability for the suitability of the product to meet the requirements from specifications, codes, or regulations in any particular application. Refer to the product TDS for specifications, test results and other attributes. The end user is solely responsible for determining the product used in any particular application. Refer to the product SDS and Product Stewardship Guidelines (A14009) for guidance on the safe and proper application of the product.