The core NFRC metrics
NFRC defines U-Factor as a measure of heat transfer (lower is better for retaining heat), SHGC as solar heat admitted through the product, visible transmittance as daylight admitted, and air leakage as air passing through the assembly.
- ✓U-Factor: lower means less heat transfer
- ✓SHGC: lower blocks more solar heat; the preferred value is climate-dependent
- ✓VT: higher generally means more visible daylight
- ✓Air Leakage: lower means less air infiltration
- ✓Condensation Resistance: higher means greater resistance to condensation
Use ratings for the exact product
Ratings can change with glass package, frame, spacer and configuration. Verify the exact labeled or certified configuration rather than relying on a marketing claim for an entire product family.
Use the numbers
Turn benchmarks into a project range
Change window count, frame material, style and location in the estimator. It returns a planning range and shows the assumptions instead of hiding them.
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