If you want to improve your home’s energy performance, one of the most useful numbers to understand is the Solar Heat Gain Coefficient, or SHGC. It tells you how much of the sun’s heat a window lets into your home, and getting it right for the North Texas climate can mean a cooler house and a smaller cooling bill.
What Is the SHGC Rating?
The SHGC rating is a number between 0 and 1 that measures how much solar heat passes through a window. A window with an SHGC of 0.25 lets in 25 percent of the sun’s heat and blocks the other 75 percent. The lower the number, the more heat the window keeps out. You will find the SHGC on the window’s NFRC label, the white sticker most manufacturers attach to new units, right next to the U-factor.
In short, SHGC measures heat gain from sunlight, while the U-factor measures how well a window slows heat moving through it by conduction. Both matter, but in a hot climate like ours, SHGC is usually the number that decides how comfortable a room stays in summer.
Why SHGC Matters for Your Energy Bills
When sunlight pours through glass with a high SHGC, that heat builds up inside the room. Your air conditioner then runs longer and harder to fight it, which drives up your utility bills and shortens the life of the system. A window with a well-matched SHGC blocks much of that heat before it ever enters, so the HVAC system does less work and cycles less often.
There is a second benefit beyond comfort and cost. The same solar energy that heats a room also fades flooring, furniture, artwork, and window treatments over time. A lower SHGC reduces that fading along with the heat, helping protect what is inside the room as well as the room’s temperature.
What Is a Good SHGC Rating by Climate?
There is no single “best” SHGC, because the right number depends on where you live and which direction the window faces. Here is a general guide:
- Hot, cooling-dominated climates (including North Texas): aim for a low SHGC, around 0.25 or lower, to keep summer heat out.
- Cold, heating-dominated climates: a higher SHGC, often 0.40 or above, is helpful so free solar warmth offsets heating costs in winter.
- Mixed climates: a moderate SHGC in the 0.30 to 0.40 range balances summer heat gain against winter warmth.
- South- and west-facing windows: these take the most direct sun, so a lower SHGC pays off most here.
- North-facing windows: these get little direct sun, so SHGC matters less and you can prioritize the U-factor instead.
For homes in Sherman and Denison, where the cooling season is long and intense, a low SHGC is almost always the right call on the sun-facing sides of the house.
What Affects a Window’s SHGC
The SHGC you see on the label is set by several features working together:
- Low-E coatings are thin, near-invisible metallic layers on the glass that reflect solar heat and are the single biggest lever on SHGC.
- Tints and glazing type change how much light and heat the glass admits.
- The number of panes matters, since double- and triple-pane units paired with low-E perform better than single-pane glass.
- Gas fills such as argon between the panes improve overall performance.
- Frame and spacer materials influence the whole-window rating, not just the glass.
Beyond the window itself, shading from eaves, awnings, trees, and the way a window is positioned all change how much sun actually reaches the glass, which is why placement and exterior shading are part of any sensible plan.
Getting the Right Rating for Your Home
Because SHGC trades off against winter warmth and changes by orientation, the smartest approach is to look at the home as a whole rather than buying one rating for every opening. The goal is to block the most heat where the sun hits hardest, while keeping enough natural light and warmth where it helps. A qualified contractor can read the NFRC labels with you, factor in your home’s exposure and shading, and recommend the right glass package for each side of the house.
Frequently Asked Questions
Is a high or low SHGC better? It depends on your climate. In a hot, cooling-dominated area like North Texas, a low SHGC is better because it keeps summer heat out and lowers your cooling load. In cold climates, a higher SHGC can be an advantage because it lets in free solar warmth during winter.
Where do I find a window’s SHGC rating? On the NFRC label, the white energy-performance sticker on most new windows. The SHGC is listed alongside the U-factor and other ratings. ENERGY STAR also publishes recommended SHGC levels by climate zone.
Does a lower SHGC make a room darker? Not necessarily. SHGC measures heat, not light. Visible transmittance is the separate rating for how much daylight comes through, so modern low-E glass can block solar heat while still letting in plenty of natural light.
Thinking about more energy-efficient windows or a roof that helps keep your home comfortable? Trust Lankford Roofing & Construction LLC. We have served local homeowners since 1937. To talk through your options, call us at (903) 465-7677 or (580) 920-1433, browse our other services, or fill out our contact form. We proudly serve clients in Sherman and Denison, TX, and the surrounding communities in Texas and Oklahoma.