As houses get tighter and energy codes stricter, it has become increasingly common for builders to apply one or more layers of rigid foam to the outside of wood-framed shells, then install horizontal siding over vertical strapping. The method adds R-value to the walls, cuts thermal conduction through the framing, and when done carefully, creates a flashed drainage space for any water that makes it through the cladding layer. The technique's been covered in several JLC articles over the past few years; after reading "Building a High-Performance Shell" (5/10), my colleagues and I decided to test the strength of the...

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