What is the U-Factor?
The U-Factor rating as noted on the NFRC label refers to the measurement of how well the window or door in question will prevent heat from escaping from your home or office. NFRC U-Factor ratings for today’s windows are generally in the range of 0.15 to 1.2. The lower the number, the better the rating, and greater resistance to the transfer of heat.
What is the Solar Heat Gain Coefficient?
The Solar Heat Gain Coefficient or SHGC is the measurement of how much heat the window blocks from the sun. If you reside in a warm, southern climate such as Florida you will be more concerned with a low SHGC rating. If your home is located in Naperville Illinois or other northern climates, you may want a higher SHGC rating to take full advantage of the heat from the sun in those cold winter months.
What is Visible Transmittance?
Visible Transmittance (VT or VLT) is the measurement of how much light will pass through your windows and skylights. The VT rating scale ranges from 0 to 1. A window with a higher VT rating on the NFRC Window Energy Ratings label will allow more light will shine through.
What is a Window Air Leakage Rating?
The Air Leakage Rating as specified 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 for most windows. A lower number on the scale depicts better window performance.