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Dissecting Your Low-e Glass Ratings one UV Ray at a Time

open living room conceptEnergy conscious homeowners understand the value of a low-e glass high-performance windows; however, windows ratings can be a bit challenging to dissect and evaluate how they affect your overall home’s energy performance and how that translates to energy savings.

We’ve created the following cheat sheet to detail what you need to know to help you make the best choice for your home and your needs.

The National Fenestration Rating Council (NFRC) tests and creates window rating criteria based on their U-factor, SHGC and visual transmittance.


The U-factor measures the heat transmittance through the glass and is measured from  0.15- 1.20. The lower the value, the more efficient the window is at blocking heat.

Solar Heat Gain Coefficient (SHGC)

SHGC measures the solar radiation that passes through a window and is measured between 0 and 1. Again, if the rating falls on the lower side of the scale, then less of the sun’s heat is passing through the glass.

Visual transmittance

Visual transmittance measures the visible light transmitted through the window and is also measured on a scale between 0 and 1. The closer the rating is to 1, the more visible light is transmitted.

How do your Windows Rate?

Those are the three main criteria The National Fenestration Rating Council (NFRC) measures to determine a window’s performance. Additional ratings include air leakage and condensation measurements. Click the button below to find out how Eastern Architectural windows rate with the NFRC.

EAS windows and doors ratings brochure