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Get your free estimateTherma-Tru Window Replacement: The San Francisco Owner’s Guide
Therma-Tru window replacement in San Francisco typically runs between $850 and $1,900 per opening installed, depending on the series, glass package, and what we find when the old frame comes out. Most owners contact us after noticing a draft that wasn’t there last winter, condensation trapped between the panes, or a sash that no longer locks square. The good news: most Therma-Tru-compatible replacements are in stock at our San Francisco shop or arrive within three to five business days. If you’re staring at a fogged unit or a window that rattles every time a Muni bus rolls down Taraval, call us at (831) 480-4124 and we’ll walk you through what you’re actually looking at before anyone schedules a visit.
Which Therma-Tru Models This Applies To
Therma-Tru window replacement covers three main series we see across San Francisco homes: the Classic-Craft, the Slim-Line, and the more recent Tru-Defense impact-rated units common in west-side neighborhoods where wind-driven rain hits hard from December through March. The compatibility gotcha most owners miss is that Therma-Tru ties its sash dimensions to the original frame profile, and the frame cannot always be reused if the existing sill shows rot or the rough opening has shifted. We read the frame before anything comes off the wall, because a 36-by-48 rough opening in a 1930s Sunset District home is rarely a true 36-by-48 anymore. OEM Therma-Tru replacement sashes and glass packs run 20 to 35 percent higher than quality aftermarket equivalents, and in our experience the aftermarket options from CWS and Mr-Glass match the original specs well for pre-2015 frames. The easiest identifier: look at the bottom rail of the sash for a small foil label with the series code and glass size, or open the lock side and look for the spacer stamp on the glass edge.
Styles & brands we work with
Signs Your Therma-Tru Window Replacement Is Failing
- Fog or haze between the panes. This means the perimeter seal failed and moisture is inside the insulated glass unit. San Francisco’s marine layer finds every failed seal eventually, especially on west- and north-facing elevations.
- A sash that drops or won’t stay open. This is a failing balance system or worn pivot shoe, not the glass itself. On Therma-Tru units, the plastic pivot shoes crack first, particularly in homes where windows get opened daily during our warmer fall weeks.
- Visible daylight at the sill or top rail when closed. The weatherstripping has compressed or the frame has settled. A gap wider than the thickness of a credit card means the sash is out of square and the weather seal isn’t doing its job.
- Condensation on the inside surface of the glass every morning. This points to a failed thermal barrier or a frame leak, not just high humidity. In older Therma-Tru units without a thermal break in the frame, cool air conducts straight through and the interior glass surface drops below dew point.
- The lock mechanism binds or no longer engages. Usually a misaligned keeper or a swollen frame corner. If you have to shoulder the sash to get it to latch, the unit has settled and the keepers no longer line up.
Replacement Cost & What’s Included
We write the price before any work starts, in writing, with no invoice surprise at the end. A standard Therma-Tru-compatible double-hung replacement in San Francisco runs $850 to $1,350 per opening for clear glass, and $1,300 to $1,900 for low-E argon-filled or impact-rated glass. What changes the number: whether the existing frame can be retained or needs a full tear-out, whether rot or water damage hides beneath the sill, and whether the home requires certain glazing for west-side wind zones. Our price covers the replacement part itself, all fasteners and flashing materials, sealants (pet-safe where there is a choice), and removal of the old unit from the property. Every job is covered by our 365-Day Done Right Promise: if the finished work is not right, we come back and make it right, no debate, no countdown. We carry a workmanship warranty on the installation and pass through the full manufacturer coverage on the part.
See the difference
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AfterDIY or Call Us?
You can safely do the diagnosis without touching a single screw: check for drafts with a damp hand around the frame on a foggy morning (a foggy San Francisco morning is actually useful for spotting a draft), inspect the weatherstripping for compression, and note where condensation forms first. What you should not do is pull the sashes out and attempt a glass pack swap on your own. Therma-Tru sashes are heavy, the balance systems are under tension, and if the glass pack shatters during removal you are dealing with tempered or annealed glass fragments in your living room and a frame that no longer accepts a replacement sash cleanly. We have also seen owners chip the frame corner removing a block-and-tackle balance, and that damage turns a $900 job into a $1,700 job. If you have already pulled the sash and want a professional to save the frame, call us at (831) 480-4124. We will tell you straight whether the frame is worth saving before we touch it.
FAQs
In San Francisco, a Therma-Tru window with a healthy frame and intact seals lasts 25 to 35 years before the glass pack begins to show its age. Units with direct western exposure may show perimeter seal fatigue closer to 15 to 20 years. Call (831) 480-4124 for an assessment if you are seeing fog or drafts on a unit installed in the early 2000s.
Yes, in many cases the weatherstripping, balance system, or lock hardware can be replaced without swapping the entire sash or glass pack. Full glass pack replacement only makes sense when the seal has failed and moisture has entered between the panes. For collapsed or fogged Therma-Tru sashes in San Francisco, you are usually looking at replacement, and we’ll show you what we see before we recommend the bigger repair. Call (831) 480-4124 and we’ll walk you through the decision.
A single-sash replacement or glass pack swap takes 45 to 90 minutes on site once the part is in hand. A complete frame tear-out and reinstall with trim runs a half to a full day depending on the amount of rotted wood we find underneath. We’ll give you a specific time window when we schedule, and we’ll call ahead before the crew arrives. Estimates are free at (831) 480-4124.
We keep common Therma-Tru glass pack sizes and balance systems on our truck and at our San Francisco shop, so many replacements happen the same day. Less common series, like the Tru-Defense impact-rated units, usually arrive in under a week. When you call, have the measurements from the bottom rail label and your series name handy, and we can check stock immediately. Call (831) 480-4124.
No. We write the price before any work starts, and the number we agree to is the number you pay. If we open a wall and find unexpected damage, we stop work, show you exactly what we found, and give you a new written number before any additional work happens. You are never billed for a surprise. Call (831) 480-4124 with your window measurements and we’ll start the quote over the phone.
Yes. Along with Therma-Tru, we stock and install replacement parts for PGT, CGI, and CWS windows, so if your San Francisco home has a mix of brands across different rooms, one call covers it. We’ll match the replacement to the specific frame rather than forcing a one-size-fits-all part onto any opening. For an exact quote on any window part, call (831) 480-4124.
Call Lightwell Windows San Francisco
We’re the local, independently operated Cedarwell windows-and-doors company in San Francisco, and we answer the phone with a live person, 24/7. When we arrive, the crew wears shoe covers, lays drop cloths on the floors, and sends a photo of the clean-up before we leave. We follow our C.A.R.E. values on every job: Clean up like it’s our own home; Ask before we move or touch anything; Respect your family’s time and quiet hours; Explain the price before the work. A light well is what brings daylight deep into a building. That’s what a well-installed window should do for your home. If you have a fogged or drafty Therma-Tru window in San Francisco, call Keith Yamada and the Lightwell Windows team at (831) 480-4124 for a free replacement estimate. We’ll put the price in writing before any work starts, and we’ll treat your house like the home it is.
Written by Keith Yamada, Owner, Lightwell Windows San Francisco at Lightwell Windows San Francisco, serving San Francisco and nearby areas.
Six Reasons Homeowners Choose Lightwell Windows San Francisco
Laminated glass and reinforced frames hold up to wind-driven rain, hail and flying debris, so your openings stay sealed when the weather turns.
Low-E insulated impact glass from our manufacturer lines commonly cuts monthly cooling bills 20-30%.
Laminated impact glass shuts out up to 40% of outside noise - traffic, neighbors, weather.
Monitoring services run $30-90 a month. Laminated impact glass resists forced entry around the clock, with no subscription.
Tighter seals and insulated glass even out hot and cold rooms and stop the drafts at the frame.
A full impact package upgrades curb appeal, buyer confidence and appraised value in one project.