What Ontario Homes Need From a Replacement Window
Ontario sits in IECC climate zone 3B, which sets the energy-performance bar for any window installed here. Below that, a short list of Ontario's longest-licensed window contractors can turn a spec into an actual installed window.
Licenses checked · California Contractors State License Board
3BIECC climate zone · ENERGY STAR South-Central zone
Ontario's climate zone, in plain terms
Riverside-San Bernardino-Ontario, CA runs a January average near 56°F and climbs to about 79°F by July, a swing that adds up to roughly 1,293 heating degree days most winters, with 1,970 on the summer cooling side of the ledger.
That load is the actual argument for paying up for a better U-factor in Ontario, separate from anything a brochure claims.
Zone 3B's requirement is the floor; Ontario'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 1.4 mi away.
What FEMA's risk data says about Ontario
San Bernardino County's hail risk sits at Relatively Moderate and its wildfire risk at Very High, according to FEMA's National Risk Index.
Hail risk matters for glass and screen durability in Ontario; 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 Ontario installer before you settle on a product line.
- Strong wind
- Relatively High
- Winter weather
- Relatively Low
Data: FEMA, National Risk Index for Natural Hazards - County-level table, v1.20 (v1.20, December 2025).
Guides to finish before Ontario 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.
Ontario's longest-licensed window installers
Oldest license first, newest last, pulled directly from the state's file. This list isn't for sale.
- Spec Construction CO INCVerify license
- LmiVerify license
- So-Cal ShowerdoorsVerify license
- E B A GlassworksVerify license
- Villalobos Glass CO INCVerify license
- Myco ConstructionVerify license
- Innovative Glazing SolutionsVerify license
- Smith Brothers Glass INCVerify license
- Design Windows & Doors INCVerify license
- Rynoclad Technologies INCVerify license
- Forrest Glass & DoorVerify license
- Fresno Shower Door INCVerify license