The closed-cell is a class 2 vapor barrier and does not absorb water. This feature prevents mold and mildew from taking hold in the assemblies. Also, close-cell foam insulation is not a food source for insects of vermin. Old wood structures can achieve todays building code requirements without changing a frame. Enjoy more privacy and quiet using open-cell spray foam, a low density foam meant for use in interior walls and between floors that allows enough absorption to provide sound attenuation in a variety of applications.