Plywood Structural Insulated Panels

Plywood SIPS (Structural Insulated Panels) are high-performance building systems that consist of an insulating foam core sandwiched between two sheathing layers of plywood. SIPs offer insulation value and structural strength to the walls of a home. Building with SIPs is quicker than traditional construction, as the pre-manufactured panels are assembled off-site in an environmentally controlled facility. The foam core can be made with polyisocyanurate foam, polyurethane foam, extruded polystyrene foam (XPS), expanded polystyrene foam (EPS), or composite honeycomb (HSC). SIPs are airtight, so vapor barriers are not required, but interior wall coverings must be added.

R-values of SIPs are sometimes overstated by manufacturers, so be sure to take a second look when doing your research. SIPs are often better insulated than a traditional stud wall due to reduced thermal bridging, however, some SIPs are too thin to accommodate super-insulation. This may provide challenges for very cold climates or achieving Passive House Standards. Look for panels that are at least 8 to 10 inches thick. You should also consider the type of insulation, and whether or not it off-gasses volatile organic compounds (VOCs).

Plywood SIPs provide a continuous insulating layer with no thermal breaks or bridges. They make air-sealing easier and don’t require an additional air barrier. On-site construction is faster than traditional building since there are fewer gaps to seal.

The first structural insulated panel using a foam core was created in 1952 by Alden B. Dow, son of the founder of The Dow Chemical Company.