Bay Area Siding Company installs replacement and new-construction windows for Union City homeowners across the bay plain of southern Alameda County — from the older cottages in Decoto and Alvarado to the postwar and mid-century tracts that make up most of the city. We're a Marin-based (Larkspur) siding and window contractor, and we manage the whole job: measuring, energy and glazing selection, permitting, removal, flashing and air-sealing, and a final walkthrough.

Ready to move forward? Request an estimate or call (415) 619-5167.

Signs it's time to replace your windows

Union City has a lot of mid-century tract homes still running their original aluminum-frame or early dual-pane windows, and plenty of older single-pane units in the Decoto and Alvarado neighborhoods. They tend to give themselves away:

• Aluminum frames that sweat and feel cold — uninsulated metal conducts heat straight through and drips condensation on winter mornings.
• Fogging or moisture trapped between the panes — a blown seal on a dual-pane unit, which can't be repaired, only replaced.
• Sashes that stick, drop, or won't lock — worn rollers and balances, or frames racked out of square.
• Rooms that never quite hold their temperature and rising heating bills, driven by single-pane glass with no Low-E coating.
• Rot, soft frames, or staining at the sill or the surrounding trim.

If a couple of these sound like your house, replacing is usually the better long-term move than another round of repairs.

What to look for in a replacement window

Three decisions carry most of the outcome:

• Energy performance. Dual-pane insulated glass with a Low-E coating is the baseline. California's Title 24 energy code sets maximum U-factor and SHGC values for replacement windows, and the units you install have to meet the code in force at permit time — the numbers shift by climate zone and code cycle, so your installer should confirm the current targets rather than quote a figure from memory.
• Frame material. Vinyl, fiberglass, aluminum-clad wood, and aluminum each balance cost, thermal performance, and looks differently. On a mid-century Union City tract, a clean vinyl or fiberglass frame often suits the horizontal lines, while an older Decoto or Alvarado home may look best with clad-wood or a profile that respects the original opening.
• Retrofit vs. new-construction. A retrofit (insert) install keeps the existing frame and is less invasive; a new-construction install takes the window down to the framing so the flashing can be fully renewed — the right call where there's rot or past water intrusion. We do both.

Comparing brands? Start at our window hub, /bay-area-window-replacement/, then read the specifics for Anlin, Milgard, Andersen, Marvin, and Pella. We also install aluminum windows.

What to expect: our process

1. Consultation — we look at your existing windows, openings, and goals.
2. Measure — precise field measurements for every opening.
3. Product & energy selection — glass package, frame, and finish chosen to meet current Title 24.
4. Permit — window replacement in Union City is permitted through the City Building Division.
5. Removal & prep — old units out, openings checked for rot or damage.
6. Install, flashing & air-seal — set level and plumb, flashed and sealed against water and air.
7. Finish & walkthrough — trim, caulk, an operation check, and cleanup together.

Union City-specific things to know

Permits and Title 24. Window replacement is a permitted alteration through the City of Union City Building Division; it's not on the city's "Work Not Requiring a Construction Permit" list. Because California treats a window swap as an energy-code alteration, a Title 24 compliance form for the fenestration is part of the submittal. We prepare that and handle the permit as part of the job.

Safety glazing, not fire glazing. Union City sits on the bay plain and is not in a Very High/High Fire Hazard Severity Zone, so there's no Wildland-Urban Interface rule forcing tempered, multi-pane glass across the whole house the way there is in the East Bay hills. What does still apply is the Building Code's standard safety-glazing rule for hazardous locations — windows in and near doors, in bathrooms and tub/shower areas, close to walking surfaces, and low to the floor generally need tempered glass — along with egress sizing for bedroom windows. We flag which openings those rules touch during scoping.

Older housing and comfort. The city's mid-century tracts and older Decoto and Alvarado homes frequently still hold single-pane or early aluminum windows, so the jump to a modern dual-pane, Low-E unit is one you feel right away — quieter rooms, fewer drafts, and steadier temperatures through both the foggy winters and the warmer late-summer afternoons inland from the bay.

Already thinking about the exterior envelope? We also do James Hardie siding and siding replacement in Union City, and we serve the wider East Bay. See finished work in our project gallery.

What affects the cost

We don't quote prices online because every home is different. The drivers are the number and size of openings, frame material and brand, retrofit vs. new-construction, whether any openings need tempered safety glazing or egress-sized units, the condition of the existing framing (rot repair adds scope), and access — upper-story openings take more setup.

Frequently asked questions

Do I need a permit to replace windows in Union City? Yes. Window replacement is permitted through the City of Union City Building Division and isn't on the city's no-permit list, and a Title 24 energy form is part of the submittal. We handle the permitting.

Do my windows have to be tempered? Only where the safety-glazing rule for hazardous locations applies — near doors, in bath and shower areas, close to the floor or a walking surface. Union City isn't a fire-hazard zone, so there's no WUI rule requiring tempered glass everywhere; we identify the specific openings that need it before ordering.

Can I keep the look of my older Union City home? Yes. Frame material and profile can be matched to the original openings — clad-wood, and specific vinyl or aluminum profiles, all work depending on the house.

Retrofit or new-construction — which do I need? Retrofit is less invasive and reuses the existing frame; new-construction is better where there's rot or water damage and you want the flashing fully renewed. We assess each opening and recommend.

Get started

Get replacement windows sized, specced, and installed right the first time. Request an estimate or call Bay Area Siding Company at (415) 619-5167.