Replacement Window GuideSunlight fades floors, furniture, and fabrics over time, and the right glass slows that damage. ENERGY STAR reports that the coatings on certified windows reduce fading by up to 75 percent from ultraviolet light exposure. This guide explains how windows protect interiors and how to shop for that protection, with every figure tied to its source.
How much fading a coating prevents
ENERGY STAR reports that the coatings on certified windows reduce fading by up to 75 percent from ultraviolet light exposure.
The coating that delivers this protection is the same low-emissivity layer that controls heat. The NFRC glazing guide lists low-emissivity coatings among the advancements that improve a window's ability to control heat transfer, and that coating also filters much of the fading energy.
Fading and solar heat travel together
The energy that fades interiors is part of the same solar radiation that heats a room. ENERGY STAR notes that a standard double-pane window allows approximately 75 percent of the sun's heat into a home, while certified options substantially reduce that heat gain.
A window tuned to block solar heat, with a low Solar Heat Gain Coefficient, generally also cuts fading. The NFRC window ratings guide describes SHGC as the amount of solar heat that can enter a home, where a lower number means less heat gain.
Keeping light while blocking damage
Fading protection does not have to mean a dark room. The NFRC window ratings guide describes Visible Transmittance as the amount of solar light that can enter a home through a window, rated 0.00 to 1.00, where a higher number means more natural light.
Because low-e coatings target invisible infrared and ultraviolet energy rather than visible light, a window can hold a reasonable VT while still cutting fading. Comparing VT alongside SHGC shows how a given window balances daylight against sun control.
Shopping for sun control
The practical step is to read the label. ENERGY STAR requires that windows meet U-Factor and, where applicable, SHGC requirements based on climate zone, so a window certified for a sunny southern zone already carries a low SHGC.
The NFRC hot-climate guidance states that in hot climates technologies such as low-e coatings prevent hot, stuffy air, the same coatings that cut fading. For rooms with valuable finishes, prioritize a low SHGC window with a low-e coating.