Fast, Reliable Spray Foam Insulation Across San Antonio
Spray foam insulation in San Antonio needs to contend with a specific problem: attics here routinely hit 140°F in July, and the heat does not stay in the attic. It bleeds through ceilings, down wall cavities, and into upstairs bedrooms. We fix that with spray foam applied by crews who work clean, protect your floors, and put the price in writing before we start. If you are in San Antonio and your upstairs runs 10 – 15°F hotter than your living room, call (903) 437-9164 and we will come look at it. [Our Spray Foam Insulation](/spray-foam-insulation/) team serves the whole metro, from King William to Churchill Estates.
Why Thistledown Insulation San Antonio Is San Antonio’s Preferred Spray Foam Insulation Company
We are a Cedarwell-family company, founded in 2003, and our San Antonio crew works to the same Cedarwell Care Promise on every job: shoe covers at the door, drop cloths across the hallway, quiet tools when children are sleeping, and a photo of the clean-up before the van pulls away. Neil Barron leads the operation, and the standard he set is simple: every customer gets a written price before any work starts, on every single visit. No ranges that drift upward after we open the attic. No surprises on the invoice.
San Antonio homeowners call us because the work holds up. Every spray foam job we install is backed by the 365-Day Done Right Promise. If something is not right, we make it right, no debate. Calls are answered by a live person around the clock. That matters when you discover a dead attic fan on a Saturday morning in August, or when you want to know if our crew can come out to your place near Oak Hills before the weekend. We know this city’s housing stock: the 1960s slab-on-grade ranches on the west side, the two-story brick veneers north of Loop 410, the older wood-frame bungalows in Monte Vista. That local knowledge changes how we approach each attic.
Spray Foam Wall Insulation in San Antonio
Spray foam wall insulation in San Antonio is the most direct fix for homes where heat pushes through wall cavities and makes rooms uncomfortable even with the AC running. In our market, a typical open-cell spray foam wall insulation project runs $1.20 – $2.10 per board foot, while closed-cell spray foam runs $2.40 – $3.60 per board foot. For a standard 2,000-square-foot San Antonio home with uninsulated exterior walls, the full wall retrofit typically lands between $6,500 and $11,000. Your written price comes before we touch a stud.
Retrofit Wall Injection
For existing San Antonio homes, we inject spray foam into wall cavities through small access points, working from the exterior or interior depending on your siding and trim. In older King William bungalows with original shiplap walls, we usually inject from the exterior to protect interior plaster. The foam expands inside the cavity, air-seals the wall, and stops the thermal bypass that lets attic heat pour into bedrooms.
New Construction and Open Stud Walls
When we install spray foam in open stud walls during a remodel or addition, we can use closed-cell foam for both insulation and structural racking strength. In west side San Antonio ranch homes from the 1960s, this often means removing old, settled batt insulation, sealing the top plates properly, and applying foam that fills the entire cavity without gaps. The difference in room comfort is measurable within hours.
Rim Joist Spray Foam in San Antonio
Rim joist spray foam in San Antonio seals the band board where your first floor framing meets the foundation, a spot that leaks conditioned air in nearly every slab-on-grade ranch in this city. Rim joist spray foam projects in San Antonio typically run $900 – $2,400 depending on home size and access. The job usually takes one day, and the payoff is a tighter, less humid house.
Why Rim Joists Leak in San Antonio Homes
San Antonio’s slab-on-grade ranches, built in large numbers from the 1960s through the 1990s, have rim joists that were rarely sealed correctly at construction. The result is a continuous gap where outside air enters and conditioned air escapes, particularly noticeable near exterior walls and in closets on the first floor. Closed-cell spray foam applied to the rim joist air-seals and insulates in one pass, and it holds up against the humidity that south Texas brings.
Crawlspace and Pier-and-Beam Rim Joists
In older San Antonio homes with pier-and-beam foundations, like many of the bungalows in Monte Vista and King William, the rim joist is exposed under the house. We crawl in, clean the area, and apply closed-cell foam that keeps crawlspace humidity out of your living space. It is miserable work in August, but the crews do it carefully and clean up after themselves.
Trusted Brands We Service in San Antonio
We install spray foam from Icynene, Demilec, and Owens Corning, plus residential insulation from Johns Manville, Knauf, Rockwool, CertainTeed, and GreenFiber. Having multiple brands available matters in San Antonio because the right product depends on your home’s age, construction type, and whether you have pets or children at home. We stock local parts and keep foam rigs in San Antonio, so scheduling and lead times are short, and we can match a product to your specific attic rather than pushing whatever is on the truck. If you want a specific brand, say so and we will quote it.
Common Spray Foam Insulation Problems We See in San Antonio Homes
- Compressed R-11 fiberglass batts in 1970s-2000s production attics: In neighborhoods like Oak Hills and Churchill Estates, original attic insulation is often compressed to less than three inches after decades of heat. That leaves upstairs bedrooms 10 – 15°F hotter than downstairs until the insulation is removed and replaced.
- Open-cell foam installed without a proper vapor barrier in humid wall cavities: In older wood-frame bungalows in King William, we have seen open-cell spray foam trap moisture behind the foam in wall cavities, creating conditions for hidden mold growth. The fix requires removing the foam, addressing the vapor barrier, and reinstalling correctly.
- Spray foam over settled batt insulation without removing it first: Applying foam directly over old, compressed batts leaves thermal bypasses at the top plates of 1960s slab-on-grade ranch homes, so attic heat still leaks into wall cavities through the framed junction above each wall.
- Foam sprayed against the roof deck with inadequate attic ventilation in two-story brick veneers: On the north side, we see homes where closed-cell foam was applied directly under the roof sheathing without addressing ventilation. During San Antonio’s frequent 100°F days, that can superheat the shingles and shorten roof life.
Pricing for Spray Foam Insulation in San Antonio, TX
We Also Serve Cities Near San Antonio
Beyond San Antonio proper, our crews regularly work in Cibolo, Floresville, Boerne, and New Braunfels. If you are in one of those communities and need Spray Foam Insulation in San Antonio standards without the big-city runaround, call us. We schedule from our San Antonio office and send uniformed, background-checked technicians to every job.
Serving San Antonio, TX - Our Local Coverage Area
We’re based in the San Antonio area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About Spray Foam Insulation in San Antonio
Yes, we fix that exact problem regularly. The cause in San Antonio is almost always degraded or inadequate attic insulation plus air leakage through the ceiling plane, which lets 140°F attic heat push into upstairs rooms. The fix is removing old insulation, air-sealing, and applying spray foam to the attic floor or roofline until the upstairs comes within 2 – 3°F of the downstairs. Call (903) 437-9164 for a written quote.
Closed-cell is better for the roof deck in most San Antonio homes because it blocks both heat and moisture, and it is the right choice against San Antonio’s high summer humidity. Open-cell is a good option for attic floors and interior walls where budget matters. We will recommend the right product for your attic after looking at it, and the price is in writing before we start. Call (903) 437-9164.
No, and we will not do it. In San Antonio homes, particularly the 1960s-2000s production builds, leaving compressed batts under spray foam creates thermal bypasses at top plates and wall junctions. Heat still leaks through those gaps. We remove the old insulation, air-seal the framing, then apply foam. It costs more up front and actually solves the problem. Call (903) 437-9164 and we will walk you through the numbers.
In San Antonio’s hot, humid climate, open-cell spray foam in an exterior wall without a proper vapor barrier can trap moisture and lead to mold in older wood-frame homes. We specify closed-cell foam for exterior wall retrofits in slab-on-grade ranches because it acts as its own vapor barrier. We will check your wall assembly before quoting anything. Call (903) 437-9164.
Yes. In San Antonio, we have measured a 14°F upstairs-downstairs split disappear within a day of a spray foam retrofit. The fix is the same whether your home is in Oak Hills, Churchill Estates, or anywhere else in the metro: remove degraded insulation, air-seal, and apply spray foam. The upstairs becomes livable by mid-afternoon. Call (903) 437-9164 for a free estimate.
Contact Thistledown Insulation San Antonio
If your San Antonio home has rooms that are unusable in the summer, or your attic insulation is decades old and compressed, we will come look. You will get a written price before anything starts, shoe covers and drop cloths on every visit, and a photo of the clean-up before our crew leaves. Call (903) 437-9164 now for a free estimate.
Written by Neil Barron, Owner at Thistledown Insulation San Antonio, serving San Antonio since 2003.