Reviewed by Residential Construction & Building Code Editorial Board
Selecting and installing high-performance fenestration: Low-E argon glass, Solar Heat Gain Coefficient by climate zone, back-dam sill pans, and AAMA flashing integration.
Proper window replacement balances thermal performance ratings (NFRC certified U-Factor and SHGC) with water-tight rough opening flashing geometry.
1. Deciphering NFRC Energy Performance Labels
Rating Metric
Definition
Recommended Cold Climate
Recommended Hot Climate
U-Factor
Rate of heat loss through window assembly
≤ 0.25 (Triple pane Low-E)
≤ 0.30 (Double pane Low-E)
SHGC (Solar Heat Gain)
Fraction of solar radiation admitted through glass
≥ 0.35 (Free winter solar heat)
≤ 0.23 (Blocks summer radiant heat)
Air Leakage (AL)
Cubic feet of air passing through window per minute
≤ 0.1 CFM/sq. ft.
≤ 0.1 CFM/sq. ft.
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Residential Construction & Building Code Editorial Board
Our team of licensed general contractors, structural framing specialists, and MEP engineers audits all content against the International Residential Code (IRC), NEC 2023, and ACCA standards.
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