Extruded polystyrene foam
Extruded polystyrene (XPS) foam is a closed-cell insulating foam used in construction. Its resistance to moisture, in conjunction with its strength, durability, and long-term R-value, make it an excellent insulation material in both roofing and sheathing applications. Because polystyrene is a thermoplastic material, it can be re-melted and re-inserted into the manufacture of new XPS insulation, thus reducing waste. In addition to being recyclable, XPS foam is re-usable in reroofing situations.