The most thermally-inefficient parts of a high-performance residential building are the windows. The insulating values are usually in the range of R-3/inch (typical) to R-10/inch (very high-quality). When compared to typical wall insulation of R-21/inch, thermal movement is going to take the path of least resistance—the windows. Even more importantly, if you want to realistically understand how a building component performs, you need to accurately evaluate it. Passive House windows…