Low-E Glass Explained: Choosing the Right Glass for Texas Homes
Updated: Oct 7
"Low-E" shows up on almost every window quote. It is one of the most important choices you will make for comfort in a Texas home, and it is rarely explained well. Here is what it means.
What Low-E means
Low-E stands for low emissivity. It is an ultra-thin, nearly invisible metallic coating on the glass. It lets most visible light through, so rooms stay bright, while reflecting a large share of infrared heat and blocking much of the UV that fades floors and furniture.
The two numbers to know
Solar Heat Gain Coefficient (SHGC) measures how much of the sun's heat comes through the window, on a scale from 0 to 1. Lower is better for keeping heat out.
Visible Transmittance (VT) measures how much daylight comes through. Higher means brighter rooms.
A good Texas glass package keeps SHGC low while keeping VT reasonably high, so you block heat without making the house feel dark. Both numbers appear on the NFRC label.
Not every window needs the same glass
West-facing: the hardest-working glass in the house. Prioritize the lowest practical SHGC.
South-facing: strong sun most of the day. Low SHGC still matters.
East-facing: morning sun, usually less severe. A balanced package works well.
North-facing: little direct sun. You can favor daylight.
Shaded by trees or porches: you may be able to choose brighter glass.
Double or triple pane?
Insulated units with two panes and an insulating gas fill are the standard. Triple pane adds insulation and sound control but also weight and cost. For most Texas homes, a well-chosen double-pane Low-E unit in a quality frame is the sweet spot. Homes near busy roads may benefit from acoustic glass.
Glass is only part of the story
Great glass in a leaky frame still lets hot air in. Pair the right Low-E package with an insulated frame and tight seals. Read more in Best Windows for Texas Heat.
Get glass matched to your home
At your free consultation, Comfort by Kula recommends glass for each side of your house. We serve Austin and the Hill Country, including Dripping Springs, Lakeway & Bee Cave, West Lake Hills and Boerne.
Take our 2-minute window quiz or call 512-755-5484 for a free in-home consultation.
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