ENERGY EFFICIENCY
Energy-efficient windows: ratings and questions to ask
Performance labels can help compare products, but climate, orientation, glazing choices and installation all matter.
Ratings homeowners may see
Window labels commonly include measures for heat transfer and solar heat gain. The appropriate combination depends on climate and project goals.
- U-factor relates to heat transfer
- Solar Heat Gain Coefficient relates to solar heat admitted
- Visible Transmittance relates to visible light
- Air Leakage ratings describe air movement under test conditions
Glass and glazing options
Double- or triple-pane assemblies, low-emissivity coatings, gas fills, spacers and tinting can affect thermal performance, solar gain, visible light and cost.
Installation still matters
Opening preparation, perimeter sealing, insulation and water management remain important even with a high-performance product.
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