09/07/2026
Most homeowners pick replacement windows by style and price. The two numbers that actually tell you a lot about a window's energy performance are almost never explained at the point of sale.
Here's what they mean.
U-Factor measures how quickly heat transfers through the window. Lower is better. A window rated 0.25 insulates better than one rated 0.45 β and that difference can affect your home's energy performance.
SHGC (Solar Heat Gain Coefficient) measures how much solar heat passes through the window. In Missouri winters, the right SHGC can help take advantage of useful solar heat, depending on the window's orientation and your home's design.
Andersen windows list both ratings on their products. Therma-Tru doors are also evaluated using U-Factor and SHGC ratings, and more than 85% of Therma-Tru door and glass options qualify for ENERGY STAR.
Fall is the right time to upgrade. Our team can walk you through the actual ratings before you buy.
When you last replaced a window, did anyone explain U-Factor to you?