Every certified window leaves the factory with a small sticker on the glass. Most crews peel it off and throw it away. That sticker is the NFRC label, and on a Washington job it is one of the first things an energy inspector checks. Here is how to read it in under a minute.
What NFRC is
The National Fenestration Rating Council is an independent, non-profit body that rates how windows, doors and skylights perform. A manufacturer does not rate its own product. An accredited lab tests the whole unit, frame and glass together, and the results are certified and published in the NFRC directory. That is why the label carries weight: anyone, including your plans examiner, can look the product up.
The numbers on the label
U-factor
The U-factor measures how much heat escapes through the whole window. Lower is better. It usually falls between 0.20 and 1.20. For new homes in Washington, the energy code calls for a U-factor of 0.30 or lower, so this is the number that decides whether the window passes.
For reference, the PuroCima lines are certified between 0.27 and 0.30, depending on the line and glass package.
Solar Heat Gain Coefficient (SHGC)
SHGC measures how much of the sun's heat comes through the glass, on a scale from 0 to 1. Lower means a cooler house in summer; higher lets in more free heat in winter. Low-E coatings are what move this number. Washington's residential code focuses on U-factor, but SHGC matters for comfort on big west and south facing walls.
Visible Transmittance (VT)
VT is how much daylight gets through, also from 0 to 1. Higher means brighter rooms. A good Low-E package keeps VT healthy while cutting heat. Our single hung, for example, is rated SHGC 0.24 with a VT of 0.42.
Air leakage
If shown, air leakage is listed in cubic feet per minute per square foot of window. Lower is tighter. Codes generally look for 0.3 or less.
Condensation resistance
This optional rating, from 1 to 100, shows how well the window resists moisture forming on the inside of the glass. Higher is better. Not every label shows it.
Where the label goes and when it comes off
The label belongs on the window until the energy inspection is done. Inspectors use it to match the installed unit to the plans and the energy compliance forms. Tell your crew to leave the stickers on until the inspection is signed off; pulling them early is one of the most common reasons for a re-inspection.
Whole-unit ratings, not glass ratings
Some suppliers quote a "center of glass" number, which only describes the middle of the glass and always looks better than reality. The NFRC label rates the whole window, frame included, and that is the number the code uses. If a supplier gives you a glass-only figure, ask for the NFRC whole-unit rating instead.
Quick checklist before you order
- Confirm the U-factor is 0.30 or lower for the exact size and glass package on your schedule.
- Ask for the NFRC certified product listing so you can look it up yourself.
- Check that tempered glass is specified where your code requires safety glazing.
- Make sure every unit will ship with its label attached.
Every PuroCima window is NFRC certified and ships labeled, with the certified glass package for each line listed on its product page. If you want the ratings matched to your window schedule, send it to us for a quote and we will spec each opening against the Washington code.