Denver's Climate Data and Its Top-Rated Window Pros
Denver sits in IECC climate zone 5B, which sets the energy-performance bar here no matter who ends up installing your windows. A window license file doesn't cover Denver on this site, so Google Maps supplies the 10 ranked names you see below. Checked October 2026.
Google Maps ratings checked · How we rank
5BIECC climate zone · ENERGY STAR Northern zone
Denver's climate zone, in plain terms
Denver-Aurora-Centennial, CO runs a January average near 32°F and climbs to about 75°F by July, a swing that adds up to roughly 5,765 heating degree days most winters, with 813 on the summer cooling side of the ledger.
That load is the actual argument for paying up for a better U-factor in Denver, separate from anything a brochure claims.
Zone 5B's requirement is the floor; Denver's specific load is what tells you whether beating that floor is worth the extra cost.
Data: U.S. EPA / DOE, ENERGY STAR, ENERGY STAR Version 7.0 Climate Zones by County/ZIP (Windows, Doors, and Skylights) (V7.0); Pacific Northwest National Laboratory (DOE Building America), Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (PNNL-33270) (2021 IECC), from the nearest NOAA station 0.6 mi away.
What FEMA's risk data says about Denver
Neither rating changes a window's energy label, but both are exactly what impact-resistance and design-pressure ratings are built to answer for a Denver home.
Ask specifically about design pressure and impact rating for Denver, not just energy performance, if either risk rating comes back on the high side.
- Strong wind
- Relatively High
- Winter weather
- Relatively High
Data: FEMA, National Risk Index for Natural Hazards - County-level table, v1.20 (v1.20, December 2025).
Guides to finish before Denver window bids come in
- How to Read an NFRC Window Label Four 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 Zone ENERGY 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 Zones Florida gives homeowners two paths to a protected opening. Here's how each one is tested, and where the HVHZ raises the bar further.
Denver's top-rated window installers, by Google
The order below weighs a Google rating against its review count, the same way this site weighs a U-factor against a brochure claim: on the number, not the name. Treat it as a rating, never as proof of a license, bond or HVHZ approval.
- 303 WINDOWSGoogle reviews
- Five Seasons Windows and DoorsGoogle reviews
- One Window AT A TimeGoogle reviews
- Zen Windows DenverGoogle reviews
- Renewal by Andersen Window ReplacementGoogle reviews
- True View Windows & GlassGoogle reviews
- Bellwether Windows, Siding, & DoorsGoogle reviews
- Lakewood Glass and WindowsGoogle reviews
- Window Replacement DenverGoogle reviews
- Ameritech WindowsGoogle reviews