Extruded Polystyrene: High-Performance Insulation for Construction
Extruded polystyrene (XPS) is a rigid, closed-cell foam insulation material manufactured by melting polystyrene resin with a blowing agent and other additives, then forcing the mixture through a die (extrusion) to expand and form a continuous board. This process creates a uniform, fine-celled structure with a smooth, often colored skin on both faces. The closed cells trap the blowing agent, which gives XPS its characteristic very low thermal conductivity (typically around 0.029-0.034 W/m·K), making it a high-performance insulation. Its closed-cell nature also grants it a high compressive strength and extremely low water absorption and vapor permeability, distinguishing it from its cousin, expanded polystyrene (EPS).
The primary application for XPS is as insulation in building and construction, particularly in below-grade and high-moisture environments where its moisture resistance is critical. It is used for insulating foundations, basements, crawl spaces, inverted (protected membrane) roofs, and perimeters. It is also widely used as insulating sheathing and in cold storage facilities. Beyond construction, XPS foam boards are used as structural insulated panels (SIPs) cores, in geofoam for lightweight fill in civil engineering, and for craft and modeling. While highly effective, traditional XPS has faced environmental scrutiny due to the historical use of ozone-depleting blowing agents; the industry has largely transitioned to more environmentally friendly blowing agents with lower global warming potential (GWP). Its durability, moisture resistance, and consistent insulating value secure its role as a premium insulation material for demanding applications.
