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ECO Window Systems Home Additions & ADU: The San Antonio Owner’s Guide
If you’re planning a home addition or ADU in San Antonio and want ECO Window Systems windows worked into the build, a full addition typically runs $45,000 – $130,000 installed, while a detached ADU lands between $90,000 and $220,000 depending on size, foundation work, and finish level. We stock and install ECO Window Systems-compatible framing, flashing, and glazing components for both new construction and retrofit additions, and we can usually have the window package on site within a week of final measurements. Most San Antonio owners call us when they’ve got an existing ECO window in a bump-out or sunroom addition that’s failed, or when an older addition is being rebuilt and they want the new window package to match what’s already on the house.
What we hear most often: the addition was framed years ago, the windows were never properly flashed, and now there’s moisture working its way into the sill plate. Or the homeowner wants to convert a garage into an ADU and needs windows that meet San Antonio’s energy code without blowing the budget. Either way, the window system is rarely the first thing people think about, and it’s usually the thing that causes the most expensive fixes when it’s wrong.
Which ECO Window Systems Models This Applies To
ECO Window Systems builds several series that show up in San Antonio additions and ADU projects, and the compatibility details matter more than most people expect. The ECO 5000 and ECO 7000 series are the two you’ll most often find in residential additions here. The 5000 is a mid-range vinyl line with a 2-5/8″ frame depth; the 7000 steps up to a 3-1/4″ frame with better thermal breaks and a higher DP (design pressure) rating, which matters on the north and west sides of San Antonio where afternoon sun and occasional high-wind storms punish windows harder.
Before you order anything, look at the label. ECO stamps a white and silver AAMA sticker on the inside of the frame, usually on the head or the jamb where the sash closes. That sticker gives you the series number, the glass package (often “LoE-366” or “LoE-270″), and the exact size in inches. If the sticker’s gone, pull the sash out and measure the frame depth with a tape measure, not the visible glass. The difference between a 2-5/8″ and 3-1/4” frame is the difference between a window that drops into your existing rough opening and one that requires re-trimming the whole opening.
One compatibility gotcha we run into constantly on San Antonio additions: ECO Window Systems changed their balance shoe design between 2018 and 2021. If your addition was built before 2021 and you’re replacing a single sash or a balance, the old shoe won’t seat in the new track without a retrofit clip. We keep those clips on the truck because we’d rather spend ten minutes adapting than make you wait a week for a bracket. On the OEM-versus-aftermarket question for ECO specifically: the frames are solid, but the factory glazing beads get brittle in Texas heat faster than the aftermarket replacements we stock. We install OEM glass packages whenever available, and use aftermarket structural glazing tape and bead from a Houston supplier that holds up better in South Texas UV than the original material.
Styles & brands we work with
Signs Your ECO Window Systems Home Additions & ADU Is Failing
- Condensation between the panes that never clears. This means the seal has failed and the argon or krypton gas between the glazing layers is gone. Once that happens, the window’s insulating value drops by roughly half. In a San Antonio summer, that shows up as a hot room and an AC unit that won’t cycle off.
- The sash drops when you raise it, or won’t stay up at all. On ECO 5000 and 7000 series windows, that’s almost always a failed balance shoe or a stretched balance spring. It’s a $12 part, but it turns into a safety hazard fast when a heavy sash slams shut on a hand.
- Visible rot or softness at the bottom corners of the frame where it meets the sill. This is rarely the window’s fault. It’s almost always a flashing failure from the original addition build. Water runs down the siding, hits the top of the window, and finds its way behind the nailing fin because the original builder taped it wrong or not at all.
- You can feel air moving around the sash on a windy day. The weatherstripping has compressed or the jamb liner has warped from heat cycling. San Antonio’s winter-summer swing does a number on vinyl jamb liners, especially on south-facing windows that get full afternoon exposure.
- The window is hard to lock, or the lock pulls the sash visibly out of square. That points to a settling issue in the addition’s framing, not the window itself. We see it often on older San Antonio additions built with pier-and-beam foundations that have shifted over two or three decades of clay soil expansion and contraction.
See the difference
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AfterReplacement Cost & What’s Included
For a window replacement or repair within an existing addition, the installed range in San Antonio runs $4,500 – $15,000 depending on how many windows are involved, what series you’re matching, and whether the rough openings need reframing. A full home addition with ECO-compatible windows, framing, drywall, electrical, and finishes lands between $45,000 and $130,000. ADU construction, which includes all utilities, foundation, and a full window and door package, spans $90,000 to $220,000.
If you’re replacing one or two failed ECO windows inside an existing addition, here’s how that typically breaks down in San Antonio:
- Single ECO window replacement (parts and labor): $450 – $1,200 per opening
- Sash-only replacement with balance hardware: $180 – $400 per sash
- Full-frame replacement with new flashing and trim: $800 – $2,000 per window
- New window package for a home addition (4 – 8 windows): $4,500 – $15,000
Our price is written before we start. Every time. It includes the window or part, all labor, disposal of the old unit, and a written guarantee covering the work for 365 days from the completion date. If something fails within that year, we come back and fix it at no charge. No dispute process, no conditions. Isaac Pruett runs every quote personally, and he’d rather tell you it’s a simple sash swap than sell you a full-frame replacement you don’t need.
DIY or Call Us?
There are things you can check safely before calling. Look for the AAMA sticker, measure the frame depth, and note whether the condensation is inside the glass (seal failure, replace the glazing) or on the surface of the glass (humidity issue, nothing wrong with the window). You can also check for cracked or missing glazing bead by running a finger along the inside edge of the sash.
What you should not do: attempt to remove a double-hung sash without releasing the balance tension first. Those balances are under significant spring load, and a sash that releases unexpectedly can break fingers or smash the glass. Full-frame replacement in a load-bearing wall is even more dangerous; we’ve seen additions where a homeowner pulled the old window and discovered the header wasn’t properly supported, and the wall started sagging within a week. If the frame is warped, the rough opening shows water damage, or you’re dealing with a second-story window, call (254) 269-5071. We’ll send someone who knows what they’re looking at, and you’ll know exactly who’s coming before they arrive.
FAQs
Expect 15 to 20 years from the frame and 10 to 15 from the original glazing before the seal fails, depending on sun exposure and how well the original flashing was done. South-facing windows in San Antonio tend to fail 3 to 5 years sooner than north-facing ones. A well-flashed, properly installed ECO window with a good glazing package can go longer, but the Texas sun is unkind to any vinyl and glazing system over time. Call (254) 269-5071 if you’re seeing early failure on a window that shouldn’t be failing.
Yes, in most cases the sash, glazing, or balance hardware can be repaired or replaced without pulling the entire frame. The exception is when the frame itself has warped or the rough opening shows water damage, at which point a repair just delays a bigger problem. We’ll tell you which one you have after a quick look, and the repair quote is free.
A single window replacement in an existing addition usually takes one day on site. A full window package for a new addition or ADU depends on framing and finish schedules, but the window installation itself typically spans two to four days once the openings are ready. We give you a written timeline with your written price before any work starts.
We keep common ECO balance shoes, retrofit clips, glazing bead, and weatherstripping on the truck for the 5000 and 7000 series, and we can source full sashes and glass packages from our San Antonio supplier within a week in most cases. If you need something odd, we’ll track it down and tell you exactly what it costs before we order it. Call (254) 269-5071 for a free estimate.
Written by Isaac Pruett, Owner, Mason Remodeling Co San Antonio at Mason Remodeling Co San Antonio, serving San Antonio and nearby areas.
