Energy Efficiency
What Makes a Window Energy Efficient? A Quick Checklist
A practical checklist for evaluating whether a window product is actually energy efficient, not just marketed that way.
"Energy efficient" gets used loosely in marketing. Here's what to actually check on a spec sheet:
- U-factor at or below 0.30 for the Indiana climate — lower is better.
- Low-E coating included, ideally spectrally selective for both summer and winter performance.
- Argon or krypton gas fill between panes rather than plain air.
- Warm-edge spacer technology between panes — reduces heat transfer at the glass edge, a commonly overlooked detail.
- Tight, well-insulated frame construction — multi-chambered vinyl or fiberglass typically outperforms hollow, single-chamber frames.
- NFRC label — a legitimate energy-performance product will have Nationally Fenestration Rating Council-certified numbers, not just a manufacturer's marketing claim.
If a quote or product listing can't provide actual U-factor and SHGC numbers, that's worth asking about directly — see our guide to reading quotes.
Related question
One more thing homeowners ask.
Not necessarily — price reflects brand, frame material, and features broadly, not just efficiency. Always check the actual U-factor and SHGC numbers rather than assuming price correlates directly.
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