Window U-Factor Calculator
Calculate overall window U-factor from frame and glass components, with R-value, annual heat loss, and energy cost impact.
Inputs
%
in
Results
Overall U-Factor
0.26
R-Value
3.85
Annual Heat Loss31,200 BTU/sq ft
Energy Cost/sq ft/yr$0.94
How to Use This Calculator
- Enter the Frame U-Factor, Glass (center-of-glass) U-Factor, and Frame Percentage of total window area.
- Select the Spacer Type: aluminum (thermally conductive) or warm-edge (less bridging).
- Enter the Air/Gas Gap Width in inches.
- Review the Overall U-Factor — a weighted average of frame and glass performance.
- Check R-Value, Annual Heat Loss per sq ft, and Energy Cost Impact per sq ft per year.
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