On The Build Show, Mike Conneely of Greenside Design Build breaks down the relationship between window U-factor and R-value, explaining how glass performance affects overall wall insulation. Using a simple wall-and-window example, he converts U-factor to R-value to show how a large double-pane window can dramatically reduce a wall’s effective thermal performance. Swapping to triple-pane glass significantly improves the combined R-value, while simply shrinking the window delivers only modest gains. Conneely also notes that fixed panels typically outperform operable units due to tighter seals. The discussion centers on energy efficiency, building code requirements, and how window selection influences heat loss and long-term utility costs.

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