The numbers that matter
U-factor measures heat loss, lower is better and it drives winter comfort. SHGC (solar heat gain coefficient) measures how much solar heat comes through, lower keeps summer heat out. Every legitimate quote should list both per window line.
Here the glass package matters more than the pane count. A spectrally selective low-E coating with a low solar heat gain coefficient does more for summer comfort and cooling bills than adding a third pane.
- Spectrally selective low-E with a low SHGC for west and south glass
- Argon fill for a modest efficiency bump over air
- Heat-rated frames (fiberglass or desert-rated vinyl) on unshaded elevations
- Exterior shading or a deeper sill overhang where the elevation allows
Rebates, credits, and what to verify
Federal energy-efficiency tax credits for qualifying windows have applied in recent years with annual caps, and some utilities run their own rebate programs. Rules change, so confirm current eligibility and the required performance ratings before you count on a credit, and keep the NFRC documentation with your receipt.
What the install does to the numbers
A high-performance window installed badly performs like a cheap one. Perimeter air sealing, correct flashing at the sill, and shimming so the sash operates square are what turn the label rating into real comfort. Ask how the crew seals and insulates the rough opening.
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Frequently asked questions
Is triple pane worth it in this climate?+
Usually not. In a cooling-dominated climate the payback comes from the coating, not the third pane. Spend the budget on a better low-E package with a low SHGC and a well-sealed install before you spend it on triple glazing.
Will new windows pay for themselves in energy savings?+
Rarely on energy savings alone. The honest case for replacement is comfort, noise, operation, and eliminating rot or air leaks, with utility savings as a secondary benefit.
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Tell me a bit about you and I'll tailor the plan to your home and budget. No pressure, no obligation.