Differences between Closed-Cell and Open-Cell Polyurethane Foam

When it comes time to actually put the foam product in your home or commercial building structure, you must identify whether you will use 0.5 lb. Open Cell Foam, or 2.0 lb. Closed Cell Foam. This makes a big difference in cost, application methods, and performance.

There are two major factors to understand and consider. The first is the nature of the foam. Open Cell Foam, where the tiny cells of the foam are not completely closed, are broken and air fills all of the “open” space inside the material. This makes the foam weaker or softer feeling than Closed Cell Foam.

Closed Cell Foam differs in that all of its tiny foam cells are “closed” and packed together and are filled with a gas that helps the foam rise and expand and become a greater insulator. These cells can be formulated to obtain many characteristics, the most common being size and density.

Open Cell foams typically weigh in at 0.4 to 0.5 lb. Closed Cell foam for insulation applications range in density from 1.7 lb. to 2.0 lb. The higher the density the foam, the heavier or stronger it becomes.

The advantages of Closed Cell Foam compared to Open Cell Foam include its strength, higher R-value, and its greater resistance to the leakage of air or water vapor. The disadvantage of the Closed Cell Foam is that it is denser, requires more material, and therefore is more expensive.

The choice of foam can also be based on the requirements for the other performance or application specific characteristics such as strength, vapor control, available space, etc.

Open Cell SPF has an R-value around 4.1 per inch and typically uses water as the blowing agent.

Closed Cell SPF has an R-value of around 6.7 per inch (aged R-value) and uses high R-value blowing agents.

You typically would not use Open Cell Foam below grade or in flotation applications where it could absorb water; this would negate its thermal performance because water is a poor insulator compared to air. Closed-Cell foam would be a good choice where small framing sizes need the greatest R-value per inch possible.

Closed Cell foam would be used for roofing applications.





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