Each Structural Insulated Panel (SIP) is crafted from 2 sheets of oriented strand board that have been structurally laminated and pressure-cured to a rigid core of expanded polystyrene foam insulation. The process creates a straight and predictable building product for walls, roofs, and flooring with better whole-wall R-values and energy efficiency than other methods of construction. The foam core provides an insulating layer, and larger single panels have fewer gaps to fill and seal, resulting in heating and cooling cost savings. Structural Insulated Panels by Premier Building Systems. Circle 217.