Sound deadening material with insulation qualities has proven to be very important if you want to minimize noise and maximize HVAC efficiency. Many different methods to solve these concerns have been tried and tested. The material used for the PT-A-904 is 1″ thick foam with a Mylar moisture barrier. It also includes pre-applied adhesive, so the installer only needs to measure, cut, peel backing paper and stick to the walls of the van. Spray on foam or fiberglass insulation is not recommended.