Almost everything homeowners need to know about replacement window energy efficiency in Denver can be found on the NFRC label. The label shows—in black and white—the exact level of energy performance of a window. The number indicates the rate of heat flow through the entire window, including the glass, frame, sash, and spacers. It is the ONLY measurement accepted by the US Department of Energy’s Energy Star program.
Out of these ratings, the two most important for Denver-area homeowners to consider are U-Factor and Solar Heat Gain Coefficient (SHGC). Think of these two ratings like the “miles per gallon” rating on your car. Similar to how MPG tells you how fuel efficient a car is, both U-Factor and SHGC tell you how energy efficient a window is.
Here is more info about the ratings on an NFRC label:
U-Factor: U-Factor measures the rate of heat loss on a scale of 0 to 1. The lower the U-Factor, the greater a window resists heat flow. In colder climates (like Denver), it is crucial that your windows have a LOW U-Factor, or they won’t keep your home warm! The acceptable U-Factor for windows in Denver is between 0.27 (or less) and 0.30.
SHGC: SHGC measures the fraction of solar radiation admitted through a window on a scale of 0 to 1. The lower the number, the better.While not as important as U-Factor for Denver homeowners, SHGC can impact your home’s energy use during the summer months. A good SHGC rating for windows in Denver is between 0.32 (or less) and 0.42.
Visible Transmittance: Visible Transmittance indicates the amount of visible light transmitted from a window. Numbers between 0 and 1 are possible, with numbers in most windows measuring between 0.3 and 0.7. The higher the VT rating, the more light will come through.
Air Leakage: Air Leakage (AL) measures how much air will enter a room through a square foot of window. Lower numbers means fewer drafts. The rating is expressed on an NFRC label from 0.1 to 0.3. 0.1 is considered outstanding; 0.2 is good; 0.3 is average; 0.4 or higher is unacceptable.
Condensation Resistance: Condensation Resistance is the capability of a window to resist condensation on the interior surface. Higher numbers are desired for Condensation Resistance, and are expressed between 1 and 100. 50 or less is substandard; 50 to 60 is good; 60 or more is very good.
Selecting energy efficient replacement windows can significantly contribute to your quality for the coming decades. That’s why choosing the best brand is so important.
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