A rigid cellular foamed plastic insulation material manufactured by expansion of polystyrene beads within a mold. This mold creates an open cell structure filled with air. EPS Type I is the most widely used insulation. Type I has a density of 1 lb/ft3 (16 kg/m3) ), Type II is a denser, more durable insulation of 1.5 lb/ft3  (24 kg/m3) density.