Structural insulated panels (SIPs) are a sandwich made up of foam insulation glued between two layers of sheathing (e.g., oriented strand board, magnesium oxide board, or drywall). SIP wall and roof panels are produced in a factory and come to the job site clean, dry, straight, and precisely made to the wall dimensions specified in the house plans with precut openings for doors and windows. They assemble quickly, producing a sturdy, well-sealed, well-insulated structure. Because there is minimal to no framing, the foam core provides a nearly continuous thermal blanket around the entire structure so heat transfer through the framing is greatly reduced.