NFRC Window Energy Ratings Explained

August 30, 2014

When shopping for new windows pay close attention to the NFRC Window Energy Ratings on the label. The NFRC, or National Fenestration Rating Council, is the entity that conducts the testing of windows that is required by manufacturers in order to apply the Energy Star® label on their windows.

What is a Fenestration Rating?

NRFC Window Energy Rating LabelYou’re likely wondering the meaning of the word Fenestration? The term Fenestration makes reference to any opening the wall of a building or your home. This includes windows, skylights, and all doors. Basically any entry point for light, access, or ventilation. For you scholars out there, the word Fenestration is derived from the Latin word “Fenestra” meaning “windows.”

What info is on the NFRC Label?

The NFRC Window Energy Ratings label contains:

performance ratings for your new windows. The information on the label includes the U-Factor, the Solar Head Gain Coefficient, Visible Transmittance, and Air Leakage ratings.

What is the U-Factor?

The U-Factor rating on the NFRC Window Energy Ratings label is a measurement of how well the window or door will prevent heat from escaping from your home. NFRC U-Factor ratings are generally in the range of 0.15 to 1.2 for today’s windows. The lower the number, the better the rating! Windows with lower U-Factor ratings offer greater resistance to the transfer of heat and have better insulating properties.

What is the Solar Heat Gain Coefficient?

The Solar Heat Gain Coefficient or SHGC is the measurement of how much heat is blocked from the sun. The SHGC scale is from 0 to 1. The lower the number, the more the window will block the sun and reduce the heat gain. If you live in a warm, southern climate such as Florida you will be more concerned with a low SHGC rating. If your home is in Naperville Illinois, you may want a higher SHGC rating to take advantage of the heat from the sun in those cold winter months.

What is Visible Transmittance?

Visible Transmittance or VT is the measurement of how much light passes through your windows and skylights. The VT rating scale is from 0 to 1. With a higher VT rating on the NFRC Window Energy Ratings label, more light will shine through.

What is a window Air Leakage Rating?

The Air Leakage Rating on the NFRC Window Energy Ratings label refers to the amount of outside air that can enter your home through your windows, doors, and skylights. Air Leakage Ratings generally fall between 0.1 and 0.3. The lower the number is, the better the performance of the window or door will be.

Searching for new windows with high NFRC Window Energy Ratings in Illinois? Contact the or call One Source Renovation (815)-634-8922.