Extruded Polystyrene

Extruded polystyrene, commonly abbreviated XPS, is a rigid closed-cell foam insulation board manufactured by extruding molten polystyrene through a die, producing a dense, moisture-resistant panel distinct from the looser, more moisture-permeable expanded polystyrene, EPS, made by a different molding process from polystyrene beads. Commercialized from the mid-twentieth century onward, its low water absorption makes it especially suited to below-grade foundation insulation, roof insulation beneath waterproofing membranes and other applications where sustained ground or water contact would degrade less water-resistant insulation materials, and its consistent, dense structure gives it reliable insulating performance over long service life.