SIP stands for Structural Insulated Panel. These panels are made like a sandwich composed of two sheets of oriented strand board (a durable and stronger version of plywood), plus rigid, extruded, polystyrene foam (EPS) which comes in different thicknesses and various predictable insulation values (based upon the value R 4 per inch of thickness). These sandwich panels provide 2-3 times the strength of a traditionally built wall, floor and roof, because they have the properties of a continuous column or I-beam. These panels don’t twist, warp or crack. Instead, they provide perfectly square and plumb walls, roofs and floors…which are a huge benefit to every builder.