What Redwood City Homes Need From a Replacement Window
Redwood City sits in IECC climate zone 3C, which sets the energy-performance bar for any window installed here. Below that, a short list of Redwood City'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
Redwood City's climate zone, in plain terms
San Francisco-Oakland-Fremont, CA runs a January average near 50°F and climbs to about 69°F by July, a swing that adds up to roughly 2,519 heating degree days most winters, with 475 on the summer cooling side of the ledger.
That load is the actual argument for paying up for a better U-factor in Redwood City, separate from anything a brochure claims.
Zone 3C's requirement is the floor; Redwood City'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 mi away.
What FEMA's risk data says about Redwood City
San Mateo County's hail risk sits at Very Low and its wildfire risk at Relatively Moderate, according to FEMA's National Risk Index.
Hail risk matters for glass and screen durability in Redwood City; wildfire risk matters more for the frame material and nearby vegetation than for the glass itself.
Either way, it's a reasonable question to bring to a Redwood City installer before you settle on a product line.
- Strong wind
- Relatively 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 Redwood City 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.
Redwood City's longest-licensed window installers
Oldest license first, newest last, pulled directly from the state's file. This list isn't for sale.
- Golden Bay Glass INCVerify license
- West Coast Glazing InstallationVerify license
- Kevin's Western Windows INCVerify license
- Innovation Glass INCVerify license