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Closed-cell foam, often referred to as rigid-foam, has a density that can range from 1.7lb per cubic ft to 2.2lb per cubic ft and an R-value varying from R-5/inch to R-7/inch. These foams have a lower vapor permeability than open-cell foams and in many cases qualify as a class I vapor retarder. Closed-cell foam is used wherever there is significant moisture or vapor drive; for instance, below grade foundation walls (basement walls), indoor swimming pools, wine cellars, freezers, etc. Closed-cell foam is also used when trying to maximize R-value in shallow cavities. Further, closed-cell foam can dramatically add to structural integrity due to its high density and compression strength. Closed-cell foam comes in two forms, water blown and 245fa blown. The water blown variety traps air inside the closed cells in order to create insulation value. The 245fa blown foam uses a lightweight gas developed by Honeywell to fill the closed cells, creating a higher R-value.
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