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Window Energy Efficiency: Visible Transmittance

Homeowners rely on windows for a variety of reasons. They allow us to see outdoors and enjoy natural sunlight without sacrificing energy efficiency or letting rain into the house. But some homeowners may wonder how much they’re sacrificing to enjoy efficient, well-sealed windows. Are you getting as much sunlight inside as you’d like?

The answer depends on a particular characteristic of your window: its visible transmittance rating, or VT. It’s easy to lose this particularly short acronym in the long list of other ratings and information on each window. To clear up any confusion, let’s take a closer look at what a VT rating is and what it means for your home.

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What is Window VT?

A window’s visible transmittance rating tells you how much visible light passes through it and into your house. Don’t confuse this with the solar heat gain coefficient (SHGC)–the VT is only concerned with light, not heat. The higher the VT rating, the more light the window allows through and the brighter your room will be.

Pro Tip: A window’s measurement of visible light includes the entire structure, even the frame–which of course transmits no light at all. A seemingly low light transmittance will thus still keep your rooms brightly lit.

Why Visible Transmittance is Important

Even as Houston homeowners hide inside from summer thunderstorms and high temperatures, we still crave natural sunlight. High-performance windows let us enjoy the sun without worrying about getting a sunburn or sweating in the high heat. Interestingly, this can also contribute to a lower energy bill, since you can choose to rely on sunlight rather than turn on a bunch of electric lights all the time.

Brightening Your House

In your search for the most energy-efficient windows, don’t forget to consider aesthetics too. Natural sunlight goes a long way toward brightening your home and making things that much nicer. Enjoy the sun without the heat!

Contact us to find your new replacement windows today.