Ashburn's Climate Data and Its Top-Rated Window Pros
Ashburn sits in IECC climate zone 4A, which sets the energy-performance bar here no matter who ends up installing your windows. A window license file doesn't cover Ashburn on this site, so Google Maps supplies the 10 ranked names you see below. Checked October 2026.
Google Maps ratings checked · How we rank
4AIECC climate zone · ENERGY STAR North-Central zone
Ashburn's climate zone, in plain terms
Washington-Arlington-Alexandria, DC-VA-MD-WV runs a January average near 33°F and climbs to about 77°F by July, a swing that adds up to roughly 4,714 heating degree days most winters, with 1,239 on the summer cooling side of the ledger.
That load is the actual argument for paying up for a better U-factor in Ashburn, separate from anything a brochure claims.
Zone 4A's requirement is the floor; Ashburn'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 3.5 mi away.
What FEMA's risk data says about Ashburn
FEMA scores Loudoun County's winter-weather risk as Relatively High and its flood risk as Relatively Moderate.
Winter risk in Ashburn weighs on U-factor and condensation resistance; flood risk weighs more on sill height and drainage detailing than on the glass package.
Treat these as two separate conversations with a Ashburn contractor, not one.
- Hurricane
- Relatively Low
- 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 Ashburn 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.
Ashburn'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.
- DryHome Roofing & Siding, Inc.Google reviews
- C2 OperationsGoogle reviews
- Windows On WashingtonGoogle reviews
- Shiner ExteriorsGoogle reviews
- Apex Energy Solutions - Window Replacement & Entry Doors - Northern VirginiaGoogle reviews
- Prime ExteriorsGoogle reviews
- Elevare ExteriorsGoogle reviews
- Christian SidingGoogle reviews
- Glass and Window SolutionsGoogle reviews
- Hodges Windows & DoorsGoogle reviews