SIPs are manufactured by combining structural board (OSB or plywood) or other facing with foam. In many cases, the SIPs use a preformed foam core and the facing is applied with an adhesive. Rigid foam cores are typically composed of either expanded polystyrene (EPS), polyurethane, or polyisocyanurate. SIPs typically range in thickness from 4 to 12 inches and can be up to 24 feet long. Roof spans are typically between 12 and 14 feet, and floor spans typically range between 8 and 16 feet. Panels may be generic without penetrations, and openings for windows and doors can be cut on the jobsite. SIPs can also be ordered as a packaged system that typically arrives at the site precut with all window and door openings installed. Electrical chases may be preformed at the factory or cut in the field.          Two structural skins give panels the necessary strength to withstand axial, bending, and racking and shear loads. Manufacturers state that SIPs can be designed to withstand winds in excess of 160 mph and meet seismic Zone 4 requirements. SIPs have excellent thermal performance-manufacturers state that buyers report energy saving in excess of 50 percent.