Understanding The Information on a Window/Door Sticker

Here is a brief explanation of what all those numbers and codes mean on the NFRC sticker that is on new windows & doors.

NFRC Label

Get a Price

Schedule Your Free In-Home, No-Obligation Quote Today.

  • I understand and agree that my in-person appointment audio may be recorded for quality and training purposes.

    By providing your mobile number, you agree to receive text messages and important links from Next Door & Window. Message and data rates may apply. Message frequency varies.

  • This field is for validation purposes and should be left unchanged.
U Factor Picture


The rate of heat loss is indicated in terms of the U-Factor. The lower the U-Factor, the better the window insulates. Energy Star approved windows and doors must have a U-Factor that is 0.32 or lower.

Five Important Variables in Every Insulated Glass Unit

Type of glass
Type of Low-E coating
Type of sealant system
Type of spacer system
Its maintenance-free characteristics

Air Leakage

Heat loss and gain can occur by air leaking through cracks in a window. The air leakage rating {AL} is the equivalent cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the window. Select windows with an AL of 0.30 or less.

Solar Heat Gain Picture

Solar Heat Gain CoEfficient

The SHGC is the fraction of incident solar radiation admitted through a window, both directly transmitted and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits.

Condensation Resistance

Condensation resistance {CR} measures how well a window resists the formation of condensation on the inside surface. CR is expressed as a number between 1 and 100. The higher the number, the better a product is able to resist condensation.

Visible Transmittance

Visible transmittance {CT} indicates the amount of visible light transmitted through the window. VT varies between 0 and 1. The higher the VT, the more light is transmitted. A high VT is desirable to maximize daylight.

Schedule a Consultation Today!

(630) 280-2748


Arlington Heights

718 East Rand Road
Arlington Heights, IL 60004



815 East Ogden Avenue
Naperville, IL 60563


Burr Ridge

16W240 83rd Street
Burr Ridge, IL 60527


learn about our specials

Learn More