Does open cell foam need a vapor barrier?
Herein, is open cell foam an air barrier?
Open-cell and closed-cell foams are air barriers. But open-cell foam will absorb and release moisture vapor more freely than closed-cell foam — which is a good thing. Open-cell foam is compatible with wood construction; both materials are air barriers that can absorb and release moisture.
Subsequently, question is, which is better closed or open cell foam insulation? Closed cell foam has a higher R-value than open cell foam, usually about 6.0 per inch. This higher rating makes closed cell foam better at keeping heat in or out of a structure. Open cell foams have an R-value of around 3.5 per inch.
Regarding this, do I need a vapor barrier if I use spray foam insulation?
Since spray foam is an air barrier and insulation, it stops the air flow and moisture movement. Open cell spray foam is required by code to have a vapor barrier installed. Most of the time it this will be in the form of 3-mil plastic sheeting.
What happens if open cell spray foam gets wet?
Open cell spray foam insulation will still dry completely after getting wet. In addition, because spray foam is not a “food” for mold, there is little danger of mold becoming a problem even if it gets wet. Closed cell foams also do not absorb water, which is very beneficial in flooding zones.