Styrofoam sheets, made from expanded (EPS) or extruded (XPS) polystyrene, are lightweight insulation materials used in construction for thermal protection in walls, roofs, and sometimes floors. While not structural or decorative, they are often placed beneath concrete slabs, tiles, or roofing to improve energy efficiency. They are not adhesives or final covering materials but serve as an underlayer in flooring, walling, and roofing systems.