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A wall of glass can make a home feel spectacular. It can also make a room uncomfortable if the window package is chosen only by appearance. For a custom home, addition, or major remodel around Austin, start with the room, its sun exposure, and the performance of the complete window—not just the glass.
Read the performance label first
The National Fenestration Rating Council (NFRC) provides standardized ratings that help compare products. Ask for the label or certified listing for the exact frame, glass package, size configuration, and operating style you are ordering.[1]
| Number | What it measures | How to read it |
|---|---|---|
| U-factor | Heat transfer through the window assembly. | Lower means less heat transfer. Compare whole-product ratings. |
| SHGC | Solar heat entering through the window. | Lower generally reduces solar heat gain; consider orientation and shading. |
| Visible transmittance (VT) | Visible light passing through the assembly. | Higher generally means more daylight; it is not the same as SHGC. |
| Air leakage (AL), when reported | Air passing through the product under test conditions. | Lower means less leakage under the stated test. Installation leakage is separate. |
These ratings describe different jobs. A lower U-factor does not necessarily mean a lower SHGC, and dark-looking glass is not a substitute for verified ratings. ENERGY STAR window regions are also different from building-code climate zones; check the county-specific window region and the current criteria.[2]
Assume window A has U-0.30 and SHGC-0.25, while window B has U-0.25 and SHGC-0.20. B has lower rated heat transfer and solar gain. That does not establish its annual savings or make it the best purchase for every opening. Compare daylight, price, exposure, warranty, and installation scope. These are illustrative numbers, not local code limits or an ADDRAC specification.
Window names describe how they operate
| Style | Description | Planning question |
|---|---|---|
| Fixed / picture | Does not open. | Is ventilation or an emergency escape opening required here? |
| Single-hung | One sash moves vertically; the other is fixed. | Will the actual clear opening meet the room’s requirements? |
| Double-hung | Both sashes move vertically. | Are the extra operating and cleaning features worth the cost? |
| Slider | One or more sashes slide horizontally. | How much of the opening is usable when open? |
| Casement | Side-hinged sash opens outward. | Will it conflict with a walkway, screen, or outdoor furnishing? |
| Awning | Top-hinged sash opens outward. | Does its placement suit access, operation, and required clearances? |
Operating style influences convenience and sealing, but a product’s measured performance matters more than assuming every casement or every hung window performs alike. “Tempered” describes safety glass; “laminated” describes bonded glass layers; neither term alone establishes energy efficiency. Required safety glazing and emergency escape openings must be checked during design.
Decode the glass and frame package
Low-E coatings change radiant heat transfer. Double- or triple-pane insulated glass uses spaces between panes; gas fills and spacers are part of the package. Vinyl, fiberglass, wood, and metal frames have different maintenance and thermal characteristics. A thermally broken metal frame is a different proposition from an unbroken metal frame. DOE recommends considering the frame, glazing, gas fills, spacers, and operation together.[3]
For large west-facing glass, ask the designer to compare exterior shading and the glass package together. For a shaded room that feels dark, consider daylight needs as well as heat control. Request a window schedule that records the decisions opening by opening.
Spend on the installation as well as the product
NFRC ratings do not evaluate installation workmanship.[4] Ask how the sill, jambs, head flashing, perimeter air seal, and wall drainage layer will connect. In a remodel, clarify whether the quote is an insert replacement or a full-frame replacement and what repairs it includes. A lower window-unit price can come with a very different installation scope.
Compare complete installed packages: product identification, glass ratings, screens, interior trim, exterior restoration, lead times, warranty responsibilities, and flashing details. For a new build, avoid changing glass or operating styles after ordering without checking the consequences.
Questions to bring to your builder
- Which exact product and glass package is included?
- Are the ratings for the complete assembly?
- Which openings need safety glazing or emergency escape compliance?
- How are the windows integrated with the wall’s water and air control layers?
- Which upgrades address my actual exposure and comfort priorities?
Plan a better-built home with ADDRAC.
Planning a custom home, addition, or window-related remodel? Contact ADDRAC Construction to discuss your openings, sun exposure, finish preferences, and complete installation scope. Request an estimate built around the home you want to live in.
Request a project estimateCall (512) 948-5922 • Email josh@addrac-construction.com
Sources and further reading
Public guidance checked October 10, 2026. Product instructions and project-specific requirements govern the final design.
Homeowner planning guidance for Austin, Cedar Park, Leander, Georgetown, Liberty Hill, Lago Vista, Jonestown, and Dripping Springs. Code requirements, climate conditions, existing construction, and product approvals vary. The comparisons and clearly labeled examples are not ADDRAC bids, performance guarantees, or a claim of certification.