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 deg F and 40-50% relative humidity. Its R-Value is 4.9 per" 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 240 deg F.