Why We Don't Use SIPs in Our Certified Passive Houses

In our more recent Certified Passive House projects, we have moved away from using foam insulation altogether, which is a very exciting development! In the past, structural insulated panels (SIPs) were seen as a good upgrade to achieve a more energy-efficient home. However, they were often expensive and inaccessible to many people.

Unfortunately, there are many cases where SIPs do not last the test of time on their outer skins. At The Artisans Group, we have chosen not to expose oriented strand board (OSB) to the weather side, which is an element of longevity in our opinion.

In our projects, we focus on air-tight construction paired with open diffusion walls that can last over 200 years. These walls are filled with dense pack cellulose or fiberglass, both of which have extremely reduced carbon footprints and costs compared to SIPs. We also try to use as little foam as possible, as the processing and energy consumption involved in manufacturing foam is not a pretty thing for human health and the environment.

Another reason we have yet to use SIPs on one of our 12 Certified Passive House projects is their intrinsic high embodied energy. In contrast, our Larsen truss walls bear on the edge of concrete and then cantilever over the continuous foam beautifully.

A SIP could not be used in this instance because they are not strong enough to cantilever one of their skins off a bearing, and a continuous bottom plate would be an unacceptable thermal bridge. This also simplified our floating slab assembly, as we were able to wrap our foundation in insulation at least 6 inches deep for performance reasons.

Our Larsen truss walls are essentially double 2×4 walls with plywood gussets at three locations that make the outer wall cantilever off the interior core, which is load-bearing and lateral. We found on the North project that we could achieve better energy performance for less cost using a Larsen Truss wall assembly.

We chose not to use SIPs on our Certified Passive House projects for several poignant reasons. By using alternative methods and materials, we are able to create highly efficient and sustainable buildings that meet the stringent standards of the Passive House certification program.

At The Artisans Group, we are committed to pushing the boundaries of what is possible in building design and construction. We believe that our approach to building design and construction is a more effective way to achieve high performance buildings while also being mindful of the environment and human health.

Passive solar sip house