Precut panels add strength, efficiency

The outside walls and the two broad, sloping roofs of the Celebration Idea House were built with structural insulated panels (SIPs), precut units that not only speed construction but assure a tight, energy-efficient shell.

The four-foot-wide panels, which sandwich thick pieces of polystyrene insulation between plywood-like oriented strand board, are designed to glue or screw together sequentially. The longest roof panels, which measure more than 22 feet in length, can span from side wall to side wall of the bedroom wing.

Walls constructed from SIPs essentially create shear walls that help resist side-to-side movement from earthquakes. The panels not only are glued at vertical joints; they also lock together at top and bottom with continuous plates.

Because of their sandwiched design, the panels contain much less solid wood than traditionally framed buildings, creating more room for uninterrupted insulation. The six-inch walls have approximately an R-30 insulation value, and the eight-inch roof panels are almost R-40.

The panelized construction assures straight, vertical walls with precisely cut openings for windows and doors. These flat surfaces made it easier to apply siding and roofing.