SIP 02Structural Insulated Panels (SIPs) are a very common choice for enclosing a timber frame. SIPs are two pieces of oriented strand board (OSB) sandwiched around an expanded polystyrene core — they provide the enclosure and the insulation all in one. SIPs provide an energy efficient enclosure, combining high R value and a tight seal. In addition, an SIP enclosure typically goes up in a matter of days, meaning your timber frame can be fully enclosed and all but dried-in almost immediately after raising.