Energy Efficient Windows

Everything you need to know about how a window will perform is on the National Fenestration Rating Council (NFRC) label that is placed on every window. It provides information on the U-Factor, Solar Heat Gain Coefficient, and Visible Light Transmittance, all which describe a window’s thermal performance.

U-Factor
The U-Factor measures how heat flows through a window. The lower the U-Factor, the slower heat transfers through – keeping the heat in longer during winter, and out in summer. Look for a U-Factor of 0.35 or lower.

Solar Heat Gain Coefficient
The Solar Heat Gain Coefficient (SHGC) is a number that indicates how much of the suns rays that can make it hot inside your house are coming through a window. The lower, the better! So if you like to be cooler look for a SHGC of 0.40 or lower

Visible Light Transmittance
Visible Light Transmittance (VLT) is the percentage of available light that is coming through a window. The higher the VLT, the more light! A VLT of 0.50 or higher is good

Low-E
Low-E is a microscopically thin, practically invisible layer of metal oxide that is deposited on the glass during manufacturing. Low-E coatings reduce heat transfer and the amount of UV rays that cause heat gain.

NFRC
NFRC stands for the National Fenestration Rating Council, the independent third party certification organization with industry-accepted standards for evaluating and certifying energy performance. Window manufacturers test their windows to these standards. NFRC numbers are used by the ENERGY STAR Window Program, and by numerous state and local energy officials, utilities and energy groups.

ENERGY STAR
The ENERGY STAR Window Program is part of the family of ENERGY STAR programs from the U.S. Environmental Protection Agency and the U.S. Department of Energy. Look for the ENERGY STAR label on qualifying products – it is your assurance that you are buying great performance and using less energy!