What is NFRC?

NFRC is a non-profit organization that administers the only uniform, independent rating and labeling system for the energy performance of windows, doors, and skylights. Their goal is to provide fair, accurate, and reliable energy performance ratings so that consumers can look a multiple products and easily compare the thermal performance.

Do my windows and doors meet ENERGY STAR requirements?

To be eligible for the ENERGY STAR, products must be rated, certified, and labeled for both U-Factor and Solar Heat Gain Coefficient (SHGC) in accordance with the procedures of the National Fenestration Rating Council (NFRC). The performance criteria are tailored to fit the energy needs of the country’s different climate regions; Northern, North Central, South Central, and Southern. The ENERGY STAR window label and climate region map give consumers clear guidelines for determining which window products are most appropriate for the area in which they live. United Window & Door Mfg. is Energy Star qualified in all 50 states.

What is Center of Glass (COG)?

There are a variety of ways to look at a window’s thermal performance; Center of Glass is one of them.  Center of Glass Rating represents the most thermal efficient area of the glass, which is one square inch, located at the center of the glass. This rating does not represent the performance and efficiency of the overall window. 

For an accurate window thermal performance, a total/overall window test rating should be utilized.

All NFRC certified manufacturers’ window test results are listed on the NFRC web site at http://www.nfrc.org/

In the Solar Heat Gain, is the higher value better, and why?

SHGC represents the amount of solar heat that comes through the window.In cooler climates (Northern Regions), more solar heat is desired.Which means higher SHGC is better. In warm climates (Southern regions), lower solar heat is desired.Which means lower SHGC is better.

In Solar Heat Gain, why is there a difference between the values for COG and TOTAL?

The COG number is just for the glazing system. The TOTAL SHGC includes glazing system, spacer, frame, etc... Because frames usually have really low SHGC, the TOTAL SHGC comes out lower than the COG SHGC.

In the Visual Transmittance is the higher number better, and why?

VT represents how much light comes through the window. Usually, more light or higher VT is better.Customers who want privacy or lower VT go for the tinted glazing systems.

In Visual Transmittance, why is there a difference between the values for COG and TOTAL?

The VT number is just for the glazing system. The TOTAL VT includes VT for the frame, which is zero unless it is transparent. The overall VT which is calculated by area weighting “frame VT” and "COG VT". Which means that the TOTAL VT is always going to be lower than COG VT.

When making IG units that are dual glazed with Solarban60 or other Softcoat Lowe glass does it impact the U-Factor?

Double Softcoat Lowe on dual glazed units makes little impact on the U-Factor. Double Lowe configuration is mainly used to lower the SHGC.