Spec first, brand second
The right window spec starts with your climate zone, not a brand name
A U-factor that pays off in one climate zone can be the wrong number two zones over. These guides work from the code and the label, not a sales pitch.
Why climate zone comes before brand or material
ENERGY STAR certifies a window against one of four US climate zones, each with its own U-factor ceiling and, in most zones, its own Solar Heat Gain Coefficient ceiling.[1]
A window built to the Southern zone's criteria and a window built to the Northern zone's criteria are solving different problems, even if they're the same brand and the same price. Picking the zone-correct spec is a bigger lever than almost any other decision in the process.
Start here
- How to Read an NFRC Window LabelFour numbers on one sticker decide most of a window's real-world performance. Here's what each one means.
- ENERGY STAR Window Criteria by Climate ZoneENERGY STAR splits the country into four zones, each with its own numbers. Here they are, and why the Northern zone works backward from the other three.
- Impact Windows vs. Shutters in Florida's Hurricane ZonesFlorida gives homeowners two paths to a protected opening. Here's how each one is tested, and where the HVHZ raises the bar further.
- Low-E Coatings and Gas Fills: What They Actually DoTwo features hiding inside the glass do more for performance than most people expect. Here's the mechanism behind each.
- Why Windows Fog or Sweat: Understanding CondensationCondensation on a window is usually a humidity story, not a defect story, and new windows can make it more visible, not less.
Florida adds a second, stricter layer
In Miami-Dade and Broward counties, a window also has to clear the state's High-Velocity Hurricane Zone rules, which test the entire product for windborne debris impact and cyclic pressure, not just its energy performance.[2]
Those two systems, ENERGY STAR's zone criteria and Florida's hurricane-zone testing, answer different questions and neither substitutes for the other.
How to use the guides on this site
Start with the NFRC label guide to learn what the numbers on a spec sheet actually mean, then check the ENERGY STAR criteria for your zone. If you're in Florida's hurricane zone, read that guide before you talk to anyone about material or brand, since it narrows your options before price ever enters the conversation.
Window contractors by city
A top-rated tag on a city here means Google ratings stand in for the license file this site couldn't find for it.
- Houston, TXtop-rated10 top-rated businesses
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Questions people ask
Do I need to know my climate zone before I get a quote?
It helps. Knowing your zone lets you check a proposed U-factor and SHGC against the actual requirement instead of trusting that a contractor's default product is the right one for your address.
Does this site sell windows or install them?
No. It publishes climate and code guidance, plus a directory of licensed local installers. Requesting a quote runs through a separate button handled by matching partners, not through the guides.
Is a higher-rated window always worth the extra cost?
Not automatically. The value of a lower U-factor or a specific SHGC depends on your zone's heating and cooling load, which is exactly what the climate guides on this site walk through.
Sources
- ENERGY STAR Eligibility Criteria: Residential Windows, Doors, and Skylights, Final Draft Version 7.0, U.S. EPA, ENERGY STAR, accessed 2026-09-30
- High Velocity Hurricane Zones (HVHZ), SoFlo Impact Windows, accessed 2026-09-30