Read the label. Check the code. Show the homeowner.
Read the numbers on a window’s NFRC label and see at once whether it meets ENERGY STAR for the zone and the energy code, then share it with the homeowner.
From the label to a clear answer
1. The label
Read the NFRC label
U-factor, SHGC, visible light, condensation resistance and air leakage, read with the iPhone camera or typed on the web, exactly as printed.
2. The check
ENERGY STAR and the energy code
See whether it meets ENERGY STAR Version 7.0 for the climate zone and the 2021 IECC prescriptive limits. Local codes may use another edition.
3. The glass
Compare and explain the glass
Look up the glass, compare low-e options side by side, and read a safety-glass stamp to tell tempered from laminated.
4. Quiet
Estimate the sound difference
See the estimated STC and OITC of an insulating unit as you change it: a laminate, a wider air space or acoustic PVB. Shown as an estimate, never a tested rating.
What dealers and installers get
- NFRC label reading with ENERGY STAR and energy-code checks
- Share the result with the homeowner, or save it to a project
- Safety-glass stamp reading for tempered, laminated and heat-strengthened glass
- The makeup builder with U-factor, SHGC, light and sound for replacement units
- The iPhone app, and the web app on any device
Label values are whole-window numbers as printed and are never changed by GlassRef. Glass and makeup numbers are center-of-glass.
Start in a minute
- Get the iPhone app or create a free account at app.glassref.com.
- Open the NFRC label reader and point the camera at the label, or type the numbers.
- Pick the climate zone and share the result.
A real GlassRef screen.
Questions about windows
How do I know if a window meets ENERGY STAR?
Read or type the U-factor, SHGC and air leakage from the NFRC label and pick the climate zone. GlassRef compares them with ENERGY STAR Version 7.0, including the Northern zone’s equivalent-performance table, and shows what passes and what does not.
Which energy code does it check?
The 2021 IECC prescriptive window limits (Table R402.1.2). Your local code may use another edition, so check with the code official.
Does GlassRef change the label’s numbers?
No. Label values are shown exactly as printed. You can correct a misread number, and GlassRef never adjusts it.
Can it tell how much quieter a window will be?
GlassRef estimates STC and OITC for the glass unit from its layers, center of glass, shown with a ±3 range. It is checked against 218 lab tests (97% within ±3) and is never a tested rating.
Is it free?
The label reader, stamp reader, glass library, compare and every calculation are free. Paid plans add unlimited saved sheets, your logo and team seats.
GlassRef publishes reference data and shows where every number came from. It does not test, certify or approve products; product certification belongs to bodies such as NFRC, and the design professional of record signs off on what goes into a building. GlassRef is independent and not affiliated with LBNL or any manufacturer.