Evaluating the Energy Performance of a Window Or Patio Door

The National Fenestration Ratings Council (NFRC) label on the new window or patio door shows the U-Value, Solar Heat Gain Coefficient, and Visible Light Transmittance values. See above sample labels.

The U-Value measures of the rate of heat loss through a window or door. The lower the U-Value, the greater a window’s resistance to heat flow. A window with a high R-Value has a greater resistance to heat flow and higher insulation value. The U-Value or R-Value is the easiest way to determine the energy efficiency of a window or patio door.  NFRC recommends a U-Factor range of 0.20 – 1.20, look for low numbers.

Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat from the sun. This is especially important during the summer cooling season. The lower the number, the less you will spend on cooling. NFRC recommends a Solar Heat Gain Coefficient of 0-1, look for low numbers.

Visible Light Transmittance values measure how well a product is designed to effectively light your home with daylight. This could save you money on artificial lighting. The higher the number, the more natural light can enter the home. NFRC recommends a Visible Light Transmittance range 0-1, look for high numbers.

Air Leakage values measure how much air can enter a room through the window. The lower the number, the fewer drafts you will experience. NFRC recommends an Air Leakage range of 0.1-0.3, look for low numbers.

All of the windows we recommend to our customers are energy efficient. They are designed to look beautiful, keep you comfortable, and save you money on your utility bills. For more information about our replacement windows, contact us today. We provide free in-home estimates and recommend the perfect windows for your situation.