Larsen Truss
A Larsen truss is an exterior framing system that creates a thick insulation cavity outboard of the structural wall, named after John Larsen who developed it in the 1980s. The Larsen truss is built from 2x2 or 2x4 lumber attached to plywood gussets, fastened to the structural sheathing of a normal 2x6 wall. The cavity is filled with cellulose insulation, giving total wall depths of 12 to 16+ inches and effective R-values of R-40 to R-60. Larsen trusses minimize thermal bridging because they are not continuous wood members.