Larsen Truss

An engineered truss made of two long pieces of solid wood held a distance apart (typically 12 to 16 inches) by a piece of plywood or oriented strand board (OSB). A Larsen Truss is made to attach to structural above-grade walls to make them much thicker to hold more insulation, for super-efficient homes.

You and your contractor can prepare Larsen trusses on-site, or have a local shop make them. For a pre-made product, you can also look for engineered OSB I-beams, which are similar but heavier. As with all wood products, ask for Forest Stewardship Council (FSC) Certified wood.

Using a Larsen truss makes it possible to make a lightweight, affordable building with very thick walls (16 inches or more), that can contain high insulation values using environmentally friendly insulation such as cellulose. The Larsen truss uses less material than a solid wood stud of the same width, and reduces thermal bridging heat loss, due to its thin yet strong profile.

The Larsen truss was invented in 1979 by John Larsen, a renovation contractor in Edmonton, Alberta, Canada, as a way to make light, thick walls for good insulation, and that's what it's still used for today!