Napa, CA: Climate Zone, Risk and Window Requirements
Napa sits in IECC climate zone 3C, which sets the energy-performance bar for any window installed here. Below that, a short list of Napa's longest-licensed window contractors can turn a spec into an actual installed window.
Licenses checked · California Contractors State License Board
3CIECC climate zone · ENERGY STAR South-Central zone
Napa's climate zone, in plain terms
Napa County's normal precipitation runs about 26.7 inches a year, with 0.0 inches of snow, which is a separate question from energy performance but still shapes which window details matter in Napa.
Moisture and glass performance are handled by different parts of a window's spec sheet, and a Napa buyer benefits from checking both instead of assuming one implies the other.
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 2.4 mi away.
What FEMA's risk data says about Napa
FEMA scores Napa County's winter-weather risk as Very Low and its flood risk as Relatively High.
Winter risk in Napa 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 Napa contractor, not one.
- Strong wind
- Very Low
- Winter weather
- Very Low
Data: FEMA, National Risk Index for Natural Hazards - County-level table, v1.20 (v1.20, December 2025).
Guides to finish before Napa 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.
Napa's longest-licensed window installers
Oldest license first, newest last, pulled directly from the state's file. This list isn't for sale.
- Javco Window And Glass Contractors INCVerify license
- Napa Valley Glass CO INCVerify license
- North Valley GlassVerify license
- Webster Window & Door INCVerify license
- Innovative Glass Solutions INCVerify license
- Decor Shower Door And GlassVerify license