How much does a sliding glass door cost to replace?
Typical ranges, repair vs. replace, and what to look for in a new patio door.
WINDOWSLow-E, argon, SHGC: how to read a window label
Short answer: in North Texas, look for a Solar Heat Gain Coefficient (SHGC) of 0.23 or lower and a U-factor around 0.30 or lower. Those two numbers, printed on the NFRC label on every rated window, tell you most of what you need to know about how a window will handle our summers.
The NFRC label
The National Fenestration Rating Council (NFRC) is the independent group that rates window, door and skylight performance. Its label lets you compare products from different brands on the same terms. Here's what each number means.
Solar Heat Gain Coefficient (SHGC)
SHGC measures how much of the sun's heat passes through the window, on a scale from 0 to 1. Lower numbers block more solar heat. In a hot climate like ours, this is the number that matters most, especially for west- and south-facing windows. ENERGY STAR's criteria for both of its southern climate zones call for an SHGC of 0.23 or lower.
U-factor
U-factor measures how well the whole window, glass and frame, keeps heat from passing through. For windows it typically ranges from about 0.20 to 1.20. Lower is better. ENERGY STAR's current criteria call for a U-factor of 0.28 or lower in its South-Central zone and 0.32 or lower in its Southern zone.
Visible Transmittance (VT)
VT measures how much daylight comes through, from 0 to 1. Higher means more natural light. Coatings that block heat can also cut light, so compare VT if you want bright rooms.
Air Leakage and Condensation Resistance
Not every label shows these. Air leakage measures how much outside air passes through the window, and lower is better (the NFRC scale runs up to 0.3). Condensation resistance runs from 1 to 100, and higher means the window resists condensation better.
What Low-E and argon actually do
- Low-E coatings are microscopically thin metal layers on the glass. They reflect heat and block most of the UV that fades floors and furniture, while letting light through. A low SHGC in Texas almost always means a Low-E coating made for hot climates.
- Argon is a clear, harmless gas sealed between the panes. It slows heat moving through the glass better than air, which lowers the U-factor.
- Double-pane glass with a warm-edge spacer is the baseline for an efficient replacement window in DFW. Triple-pane adds cost and is rarely worth it in our climate.
Comparing quotes
- Ask for the NFRC numbers for the exact window and glass package being quoted, not the best number in the brochure.
- Compare SHGC first, then U-factor, then VT.
- Remember that installation matters too. A great window installed poorly will still leak. Read how we install.
Home energy savings calculator
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The bottom line
For a North Texas home, the label to look for reads SHGC 0.23 or lower and U-factor 0.30 or lower, with double-pane Low-E glass and argon. We'll show you the NFRC label for the exact windows we quote before you buy. Wondering what new windows will save? Read our honest answer.
Sources: National Fenestration Rating Council, understanding the label; ENERGY STAR, windows, doors and skylights criteria; Cardinal Glass Industries, ENERGY STAR 7.0 guidance.
