Most window calls start with a single complaint. The bedroom over the garage that's an oven by 4 p.m. The kitchen window that drips every winter morning. The one in the den nobody can open anymore. Then we walk the house and find the rest: brittle weatherstripping, a pane gone milky between the glass, aluminum frames cold enough to sweat. It's the same story in Santa Rosa and Windsor, where plenty of homes from the '70s and '80s still have the windows the builder put in. Those windows were fine for their day. They just weren't made to last 40-plus years, and California's energy code has moved a long way since.
Below we cover how to tell when a window is finished, what the state's fire and energy rules ask of new windows, how install day works and what actually drives the price. If you're leaning toward the lowest-maintenance option, our vinyl window replacement page goes into frames, colors and glass in more detail. A lot of homeowners start there, and for good reason: it's the best value per window in the county.
When a Window Is Done
Glass doesn't wear out, but everything around it does. The surest sign is haze or droplets trapped between two panes. That means the seal failed, the insulating gas leaked out and the window now does a much worse job than it used to. Drafts come next. On a breezy afternoon, run your palm along the edge of the sash and you'll feel the air moving. Then there's how it works: sashes that drop on your fingers, latches that won't catch, sliders that jump the track. Wood frames give themselves away with soft spots and peeling paint at the bottom corners, where rain sits. And single-pane glass is a sign by itself, even when it looks perfect. One bad window can often be fixed. When it's half the house, replacing them together saves on labor and trips.
Tempered Glass and U-Factor, Explained Simply
Two sets of state rules shape what goes into a window opening here.
The first is wildfire. If your home is inside a designated fire hazard zone, and many hillside neighborhoods from Fountaingrove to the Sonoma Valley do, California's wildfire code calls for exterior windows with multiple panes and at least one pane of tempered glass. Tempered glass is heat-treated, so it holds up to heat much longer than regular glass, and if it does break it crumbles into small pieces instead of sharp shards.
The second is energy. California's Title 24 code caps how much heat a replacement window can let through, measured as U-factor. Lower is better. On larger jobs, more than 75 square feet of new glass, the limit is a U-factor of 0.30 and a solar heat gain rating of 0.23 or less. Both numbers are printed on a label stuck to every new window, and the inspector looks for it.
How Install Day Works
We start with protection: drop cloths inside and furniture moved back from the walls. Then we work a few openings at a time so the house is never standing open. On a retrofit, the old sashes come out, the existing frame gets checked for rot and squared up, and the new window sets inside it on shims. On a full-frame job, we strip the opening to the studs, flash it against water and build it back. Either way, each window gets leveled, insulated around the edges, caulked outside and trimmed inside. Bedroom windows have to keep a big enough emergency escape opening, 5.7 square feet on most upstairs bedrooms, so we size those carefully. The last step is a walk-through: you try every window, latch and lock while we're still there, and the old units go out to our truck.
What Moves the Price Up or Down
Window pricing has a lot of parts, but none of them are a mystery. Frame material is the big one: vinyl is the least expensive, fiberglass costs more and wood costs the most. Nationally, installed prices in 2026 run roughly $450 to $1,200 per window, and Bay Area labor pushes most local quotes toward the upper half. Size and style matter too. A standard bedroom slider is simple. A big picture window, a bay, or anything with grids and custom colors adds cost. Full-frame installs cost more than retrofits because of the patching. Tempered glass for fire zones adds a little per window. What brings the price down is doing several at once, since setup and travel get spread across more windows.
If a whole new window is more than you need, look at foggy glass replacement: when the frame is sound, swapping just the sealed glass is often the smarter fix.
Common Questions
A well-made window installed correctly should give you decades of service. The part that usually gives out first is the seal between the panes, which is why the manufacturer's glass warranty matters. Vinyl and fiberglass need little upkeep. Wood lasts as long as the paint or cladding keeps water out. Installation matters just as much as the product: a unit set out of level or poorly flashed fails early no matter the brand.
Not necessarily. Plenty of homeowners start with the worst rooms, often the west-facing ones that take the afternoon sun, and do the rest a year or two later. The only catch is matching, so we note the brand, color and grid pattern to make sure the next batch lines up with the first. Doing them all at once costs less per window, but there's no rule that says you have to.
Usually not. Most Sonoma County homes get a retrofit, where the new window sits inside the old frame and the siding, stucco and inside walls aren't touched. We pull the frame, a full-frame install, when it's rotted, badly out of level or you want to resize the opening. That costs more because the walls get patched afterward, so we check every frame before recommending it.