Structural insulation panel (SIP) is a building material that consists of two outer skins enclosing a core of insulating material. The most common outer facing skins used are plywood or oriented strand board (OSB). OSB is commonly used as a facing material, as it is available in large sizes varying from 12 feet to 36 feet. The common materials used for insulation in the core are expanded polystyrene and extruded polystyrene. Another alternative is to use isocyanurate foam.