Schedule a Free Consultation

Understanding NFRC® and ENERGY STAR® Labels

Most replacement windows come with energy performance and ENERGY STAR® certification labels. But what do these labels mean?

Energy Performance Labels

Energy performance labels are the white labels provided by the National Fenestration Rating Council® (NFRC). These labels indicate performance ratings of the product’s energy efficiency. Unlike most ratings organizations, the NFRC does not categorize “good” or “bad” products. The labels simply state a particular product’s ratings. These labels can be found on fenestrations: windows, doors and skylights.

The NFRC’s ratings are divided into four categories:


A product’s insulation is measured by its U-factor or U-value. A low rating means low heat transmission and better insulation. Some literature on replacement windows refer to window insulation as R-value, which measures resistance to heat flow. Therefore, a product with a very low U-factor rating will have a correspondingly high R-value.

Solar Heat Gain Coefficient (SHGC)

SHGC measures resistance against heat gain from infrared radiation. Low values indicate less heat gain. A bay window or other window styles with large glass areas can benefit from glass with low-E coatings like our High Performance™ Low-E4® glass, which selectively blocks solar heat.

Visible Transmittance 

Visible transmittance (VT) measures how well a product allows natural light into the room. A higher VT value means better indoor illumination. The aforementioned low-E coatings make it possible to have windows that allow natural light in without heating up your indoor spaces.

Air Leakage 

Air leakage measures how much air can pass through the product. A low air leakage value means less chances of experiencing drafts.


ENERGY STAR is an initiative that’s intended to give consumers an easy way to identify energy-efficient products and make informed decisions at the point of purchase. ENERGY STAR labels give homeowners the assurance that they are buying energy-efficient replacement windows without having to delve into and compare energy ratings. ENERGY STAR ratings apply to a diverse selection of products that includes computers and washing machines.

Renewal by Andersen® of Wyoming is your leading provider of window replacement services. Give us a call at (307) 472-2199. You can also fill out our contact form to schedule an appointment. We serve customers in Laramie, Casper and Cheyenne, WY.


"We love our new windows. The install was painless even with moving around 3 dogs as the crew worked through the house. So glad we went with Anderson windows."

Apr 11, 2019

View All Reviews