SPF used in exterior roofing applications. Roofing foam nominal core density is typically 40 – 56 kg/m3 (2.5 -3.5 lb/ft3) and compressive strength is typically 280 kPa (40 lb/in2) minimum. Building codes do not limit the smoke development index (per ASTM E 84) for roofing foams; therefore, roofing foams should not be used for interior applications.