Windows are routinely rated by The National Fenestration Rating Council (NFRC) based on assessments of a window's energy performance ratings. This rating is determined by a window's U-factor, solar heat gain coefficient (SHGC), and amount of visual transmittance. These three factors are measured and considered when certifying a window as ENERGY STAR® qualified.
What's the U-factor?
The U-factor, or U-value, measures a window's ability to conduct heat and hold onto it. This value can give you an idea of how much heat is gained or lost from your window. The range for the U-value can be anywhere between .25 and 1.25. The lower the u-value, the more insulating the window is and better at retaining heat. For example, the most energy-efficient double-pane windows probably have a U-factor of .30 or lower. Some manufacturers apply low-emittance coatings and gas fillings between the panes to decrease U-factors and produce better-performing windows.
How About the SHGC (Solar Heat Gain Coefficient)?
The SHGC is a measurement that will tell you what amount of solar radiation your window lets into your home, which then transfers into heat. The range for the SHGC is typically between 0 and 1. The lower the SHGC number, the less heat it conducts. If you're looking for the best SHGC rating, you'll want to keep your eyes open for a rating of 0.25 or lower for optimal energy performance and reduced air conditioning costs. If you prefer your home to be warmer, then you might choose a window with an SHGC rating between 0.35-0.60 to allow more of that natural heat inside.
And Visual Transmittance?
Visual Transmittance (VT) measures how much visible light is passing through the glass. The higher the VT number, the higher amount of light that gets in. Double and triple-glazed windows produce VT ratings between 0.30-0.70. So if you're looking for a high-performing window, try not to purchase models with a VT value of less than 0.40.
At America's Best Choice windows, we can assist you in finding the best window that fits your energy performance needs. We provide free estimates and can advise you on window replacements. We pride ourselves on our upfront service, free of gimmicks and hidden charges. Don't hesitate to call us at 504-858-6979 or contact us to schedule a free in-home consultation today.