Efficient windows better, but how do you compare?

balance cost effectiveness with energy efficiency, as more efficient windows, doors and skylights can make a big difference in energy consumption over time.

Start by looking for products carrying the Energy Performance Ratings label from the National Fenestration Rating Council (NFRC). The label can help determine how well a product will perform. By using the label information, you can reliably compare one product with another.

Your BBB explains the terms used to describe window performance:

U-Factor: During the cold winter months, you’ll want to make sure your windows are trapping heat. U-Factor ratings generally fall between 0.20 and 1.20. The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value.

Solar Heat Gain Coefficient (SHGC): The SHGC rates how much solar radiation is admitted through the window and is expressed as a number between 0 and 1. The lower a window’s SHGC, the less solar heat it transmits in the house.

Visible Transmittance (VT): This is an optical property indicating the amount of visible light transmitted through the window. VT is expressed as a number between 0 and 1. The higher the VT, the more light transmitted.

Air Leakage (AL): Heat loss and gain occur by AL through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly.

Condensation Resistance (CR): The higher the CR rating, the better the product is at resisting condensation formation. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 1 and 100.