Closed-cell foam is non-porous, and not moisture-penetrable, thereby effectively forming a SEMI-permeable vapor barrier.  Closed-cell foams are superior insulators; it can attain R-values of 5 to 8 per inch (RSI-0.88 to RSI-1.41 per inch).  It is very strong, and structurally reinforces the insulated surface.  Unlike open-cell foam, closed-cell foam rarely requires any trimming, with little or no waste.

Posted in: Spray Foam Insulation