DuPont™ Styrofoam™ Brand Deckmate™ Plus Extruded Polystyrene (XPS) Foam Insulation is an extruded polystyrene foam featuring smooth, high-density skins and a closed cellular structure. It is designed specifically to provide a higher compressive strength and additional membrane support for conventional low-slope roof applications. Styrofoam™ Brand Deckmate™ Plus boasts excellent insulating characteristics (R-value of 5.0 [.88 RSI] per inch of thickness), low water absorption and excellent compressive strength.