Three Factors that Affect the Energy Efficiency of a Window

When it’s time to install new windows in your home, it’s important to take into account the energy performance ratings of the product. The NFRC has made it easy for homeowners to gauge the energy efficiency of their new windows through informative ratings.

Three Factors that Affect the Energy Efficiency of a Window

In this post, Winfield Builders discusses the three factors that affect the energy efficiency of a window.


Printed in an orange-colored box in the NFRC label, the U-Factor measures how well the window keeps heat from escaping your home. The average range falls between 0.20 to 1.20, with lower numbers generally being better.

R-Value often goes hand-in-hand with U-factor and refers to the insulating level of the window or how well it keeps heat in your home. The glass is the main contributor of R-value and you can improve this value with additional panes. As your local roofers and window experts, we’ll make sure your new windows have a high R-value for maximum energy efficiency.

Solar Heat Gain Coefficient

This is the rating in the purple box and tells you how well the window resists unwanted heat gain. The average range for Solar Heat Gain Coefficient is between 0.1, and just like the U-factor, you want to look for low numbers.

Visible Transmittance

This is the rating within the green box. It tells you how good the window is at admitting daylight into your home. You want high numbers of visible transmittance.

All these factors play a key role in how energy-efficient your window will be. At Winfield Builders, we’ll help you make an informed decision regarding your new windows. We strive to always offer you the most energy-efficient products for your home.

We also offer roofing and complete gutters services. Give us a call at (301) 329-8295 to learn more. We install high-quality windows in Rockville, Annapolis and Silver Spring, MD.

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