Usually no. Closed cell foam is a vapor barrier. Open cell foam is a vapor retarder, but its moisture permeability properties in our climate are sufficient for most structures. Our building science professionals can advise you as to which type of foam is best for your project. Since both of these products are air barriers, the conditions for cold and warm air to mix, condense, and cause moisture problems, do not exist if installed properly. In some cases, we recommend a spray-on vapor barrier paint, which Energsmart can install, on open cell foam — usually in the Southern Tier of Western New York.