Build With SIPs

Enlarge Image Image Gallery This home in Kansas was built with structural insulated panels, also known as SIPs. PHOTO: MICHAEL MORLEY

As an architect, I’ve been using structural insulated panels (SIPs) since 1992, when they were relatively new. Since then, I’ve designed several hundred residential and commercial projects using SIPs. In my opinion, they are superior to conventional framing systems in almost every way — SIPs are simply better insulated, stronger and faster to build with than standard stick-frame construction. SIPs also help conserve forest resources, because they produce almost no waste.

As worldwide timber quality and availability continue to decline and the costs of labor and energy increase, SIP construction should become more popular and cost-effective. I predict that in the next 10 years, the U.S. construction industry will adopt SIPs as the system of choice.

Advantages of SIPs

Structural insulated panels are typically composed of rigid foam insulation sandwiched between two skins of oriented strand board — kind of like a s’more. The exterior skins are attached to the foam core with a high-strength adhesive.

The foam core material is often expanded polystyrene — the same material used in ice chests and shipping “peanuts.” Some manufacturers use polyurethane or isocyanate foam cores. The skins can be plywood, metal or other rigid sheet materials, but oriented strand board is used by the majority of SIP manufacturers. The foam core serves as a spacer and insulator between the exterior skins. (Keep reading for more specifics about these materials, and their environmental impacts.)

Altogether, the structure acts as a monolithic whole — as opposed to stick-frame construction using 2-by-4s, where hundreds of individual nailed connections hold the studs and skins together. As a result, SIPs are twice as strong as a wood-framed house, which is a real advantage in locations that experience tornadoes or hurricane-force winds.

SIPs are also extremely energy efficient. Compared to a typical stick-frame house, a house built of SIPs will require about half the energy to heat and cool throughout the year in most climates. It’s not just the thickness of the polystyrene inside that makes SIPs more energy efficient — it’s that the whole panel is designed to function as one structural unit. The thermal “tightness” and resistance to heat flow work with the insulation value to achieve exceptional comfort and energy efficiency.

Cost and Savings

I have heard claims that SIPs are “cheaper than stick-frame or the same cost as conventional systems.” That may be true in some parts of the county where labor cost is high or skilled labor is unavailable. In my experience, using SIPs usually costs slightly more than stick framing, adding about 5 to 15 percent to the total cost of the home. (The framing, insulation and associated labor is usually only about 10 to 15 percent of the total cost of a new home.)