Nu-Foam is an expanding, polyurethane, prepolymer foam that is used as a sealant and an insulating product. It is designed to seal, fill and insulate small cracks, gaps and voids. Tack free time for Nu-Foam is less than 30 minutes at 70°F and 40-50% relative humidity. Its R-Value is 4.9 per inch thick making a very good insulator in most any application and can even provide sound-deadening. Nu-Foam is UL classified and is fire retardant. Can withstand temperatures up to 240ºF.It can be used to seal and insulate areas such as openings created for refrigeration, air conditioning and heating tubes or pipes, duct joints, utility penetrations in exterior sheeting, masonry, concrete or wood walls, and other areas where unwanted air penetration might occur.