Expanded Polystyrene (EPS)
Polystyrene, a thermoplastic polymer, is manufactured for building insulation by extrusion or molding. Extruded polystyrene (XPS) was formerly called extruded expanded polystyrene (XEPS) foam
Figure 11.1 Geofoam. (.R-Control Building Systems)
board. It is created by the process of extrusion, which results in fine, closed cells that contain a mixture of air and refrigerant gas. Extruded polystyrene is discussed in the next section.
The other manufacturing process is molding, which produces coarse, closed cells containing air. Molded expanded polystyrene (MEPS) foam board, now called expanded polystyrene (EPS), can be molded into many everyday items such as coffee cups, coolers, protective cushioning for shipping materials, or insulation boards for construction applications. This closed-cell material, often referred to as headboard in construction jargon, is less expensive than extruded polystyrene and generally is white in color.
EPS is used for a variety of building applications. These include cavity wall insulation, exterior insulation and finish systems (EIFS), exterior sheathing, perimeter insulation, and underslab insulation. Low-slope roof applications include flat or tapered roof insulation for built-up roof systems and ballasted, mechanically attached, or fully adhered single-ply membrane roof systems. Specialty products also include cores for structural insulated panels and concrete masonry unit core inserts (Fig. 11.2).