How to Read an NFRC Window Label: And Why SHGC Matters More in Houston

Every window you buy in the United States comes with a small white sticker from the National Fenestration Rating Council. Most people peel it off and toss it in the trash. That's a mistake, especially in a place like Houston, because that sticker tells you exactly how the window will behave when the AC is running from April through October.

If you're buying replacement windows and you only learn one thing from this post, learn this: in Houston, the number that matters most on that label is the SHGC. Everything else is secondary. Here's why, and here's how to read the rest of it too.

The NFRC label lists five main ratings. Each one is independently tested, so you can compare windows from different brands apples to apples. The five ratings are U-factor, Solar Heat Gain Coefficient (SHGC), Visible Transmittance (VT), Air Leakage, and Condensation Resistance.

You don't need a degree to read them. You just need to know which ones matter in your climate, and which ones matter less.

U-factor measures how well a window keeps heat from passing through the frame and glass. Lower is better. It ranges from about 0.20 to 1.20.

In northern states where winter heating is the big expense, U-factor is the star of the show. In Houston, U-factor still matters, but it plays second fiddle to SHGC. Aim for 0.30 or below and you're doing fine.

SHGC, or Solar Heat Gain Coefficient, measures how much of the sun's heat the window lets through the glass and into your home. It's a decimal between 0 and 1. Lower means less solar heat gets in.

Houston sits in climate zone 2A, which is what the Department of Energy calls cooling-dominant. That's a polite way of saying we spend most of the year fighting the sun, not the cold. Every watt of solar heat that sneaks through your windows turns into another dollar on your electric bill.

So what's a good SHGC in Houston? Experts agree you want 0.25 or below. Here's a rough breakdown you can keep in your head:

• 0.40 or higher: old-school clear glass. Your AC will run constantly.
• 0.30 to 0.39: basic Low-E. Fine for a mild climate, not great for Houston.
• 0.25 to 0.30: solid for Houston. Most builder upgrades land here.
• 0.22 to 0.25: excellent. You'll feel the difference on hot afternoons.
• Below 0.22: very few windows on the market hit this.

Our 9230 single-hung window carries a 0.22 SHGC rating. That's below the 0.25 threshold most energy experts recommend for Houston, and it beats the Cardinal LoE3 366 glass package (0.27 SHGC) that a lot of local competitors sell as their premium option.

That 0.05 difference sounds tiny on paper. In a Houston summer, on a 2,000 square foot home with south-facing windows, it can shave real dollars off your cooling bill every month. It adds up.

If you want to see the numbers for yourself, our single-hung page has the full spec sheet, or you can reach out to us directly.

Visible Transmittance is how much natural light the glass lets through. Higher is brighter. Most modern windows land between 0.40 and 0.60. Anything in that range is fine for a normal home. If the number drops below 0.40, you'll notice the room feels dimmer, so check it before you commit to heavily tinted glass.

Air Leakage tells you how much air sneaks around the sash when the window is closed. Lower is better, and anything below 0.3 is good. Star Windows seals tight, which is why they hold up so well in Houston thunderstorms and hurricane season. A leaky window also means your conditioned air is escaping and your humidity sensors in the AC are working harder than they should.

Condensation Resistance is the least critical rating for Houston. It matters more in cold climates where the inside of the window fogs up during winter. For most of our neighbors, you can safely skip it, although it can still be useful if you have a guest bath or laundry room that builds up moisture.

If you remember only one thing from this post, remember SHGC. In Houston, a 0.22 window and a 0.30 window are not the same product. They'll look nearly identical from the curb. But the lower number will keep your house cooler, your AC running less, and your summer electric bill a lot more reasonable.

Before you sign a quote, flip to the NFRC label or ask for the spec sheet. If the SHGC isn't listed, that's a red flag. If it's above 0.30, keep shopping.

Star Windows manufactures vinyl windows right here, and our single-hung 9230 hits 0.22 SHGC out of the box. We'll walk you through the full NFRC label for any product we quote, no jargon. Browse our full lineup of window types or call 281-219-3434 and we'll get you started.