Johns Manville Spray Foam Insulation in San Antonio: What to Know First
Johns Manville spray foam insulation in San Antonio homes typically costs between $2.25 and $4.75 per board foot installed, depending on whether you need open-cell or closed-cell foam. Most attics we quote fall between $4,800 and $11,400 total. We’re an independent Johns Manville service provider, not a manufacturer affiliate, and we typically schedule spray foam jobs within 5 to 10 business days of your written estimate.
This page is for San Antonio homeowners who already have Johns Manville products in their home, or who are considering them, and want straight answers about what spray foam costs, how it fails, and who will show up at the door. If you’d rather just talk it through, call (361) 213-9499 and you’ll get a live person, not a phone tree.
How Johns Manville Products Fail – and How We Fix Them
Johns Manville makes solid insulation products, but San Antonio’s heat and humidity put real stress on spray foam systems over time. Here’s what we actually see on service calls, and what we do about it.
- Open-cell foam shrinkage at the roofline. JM’s open-cell products, like the Corbond III line, can pull back slightly from the roof deck in attics that regularly hit 140°F in August. When that happens you lose the air seal at the exact place it matters most. We remove the affected section, re-prep the substrate, and reapply foam to restore the thermal boundary.
- Closed-cell foam delamination on metal studs or ductwork. We see this most often with JM’s closed-cell formulations applied to smooth metal surfaces in unconditioned spaces. The foam separates from the substrate because moisture condensed between the metal and the foam during installation. The fix is cutting out the delaminated area, drying the surface, and reapplying with a mechanical bond primer.
- Uneven foam depth from rushed original installations. Some San Antonio homes we inspect have JM spray foam that’s 2 inches thick in one bay and 5 inches in the next. That’s almost always an installation issue, not a product defect. We map the attic with a depth gauge, identify the thin spots, and fill them to the R-value the original job was supposed to deliver.
- Rim joist foam gaps behind plumbing and electrical penetrations. This is the quiet killer in San Antonio slab-on-grade homes. The foam around rim joists looks fine from the interior, but when you look from the crawlspace or exterior, you see gaps where the original installer couldn’t reach. We re-treat those rim joist cavities from both sides when accessible, using a foam that matches the existing JM product’s thermal performance.
- Open-cell foam that absorbed humidity and lost R-value. In a San Antonio attic with poor ventilation before the foam went in, open-cell JM foam can absorb moisture during our humid spring months. Once saturated, it loses insulating capacity and can hold dampness against framing. We identify the source of the moisture first, then remove and replace the compromised foam. Putting new foam over a moisture problem just moves the problem.
Our Johns Manville Spray Foam Insulation Process
Every Johns Manville spray foam job we run in San Antonio follows the same sequence, and you’ll know the price before we start. Here’s how it goes:
- 1
The call and the questions. You tell us what you’re seeing: high bills, hot rooms, drafts, or just an attic that never cools down. We ask about your home’s age, which direction your roof faces, and whether you know what type of insulation is already in place.
- 2
The attic assessment. We come out, inspect the existing insulation, identify the Johns Manville product if it’s already in place, and measure the attic. You get photos and a written explanation of what we found.
- 3
The written price. Before any work starts, you get a line-item price for the exact scope. R-value targets, square footage, foam type, prep work. No allowances, no “we’ll figure it out as we go.”
- 4
The tech briefing. We compare OEM-spec JM foam against equivalent aftermarket products that meet the same thermal and fire performance standards. If an existing JM system is under warranty, we follow manufacturer requirements so you don’t void coverage. If it’s long out of warranty, we recommend the product that fits the job and your budget, and we tell you why.
- 5
The install and test. Our crew applies the foam, checks depth with a gauge, verifies the air seal with a smoke pencil, and cleans up. You get a walkthrough of the finished work before we leave.
- 6
The written guarantee. Every job carries our 365-Day Done Right Promise. If something isn’t right, we come back and fix it free within the year. That’s labor and materials, in writing.
What Johns Manville Spray Foam Insulation Costs in San Antonio
Here’s what you can expect to pay for Johns Manville spray foam work in the San Antonio area, based on the jobs we quote most often:
- Open-cell spray foam, full attic roofline (1,500 sq ft home): $5,200 to $7,800
- Closed-cell spray foam, full attic roofline (1,500 sq ft home): $8,500 to $12,500
- Closed-cell spray foam, rim joists only (standard 2,000 sq ft home): $1,400 to $2,600
- Open-cell garage ceiling (2-car garage): $1,600 to $2,900
- Spot repair of failed or compromised foam (under 100 sq ft): $600 to $1,400
- Filling thin or uneven foam in existing attic (partial re-spray): $2,800 to $5,600
What moves the price: open-cell vs closed-cell, roof pitch, access difficulty, whether old insulation needs removal first, and how much of your existing foam is salvageable. You’ll get the exact number in writing before we order a single drum of material. Call (361) 213-9499 for a free estimate.
Why San Antonio Homeowners Call Aspen Attic Insulation San Antonio for Johns Manville Work
We’ve been running crews in San Antonio for over a decade, and the homeowners we work with tend to ask the same two questions: who’s actually coming to my house, and what’s this really going to cost. Both get answered before you commit to anything.
Every technician we send is background-checked, identity-verified, and arrives in a marked uniform with a photo ID badge. You’ll get their name and photo sent to you before the visit. If someone else shows up claiming to be from us, the visit is free and we make it right. That’s part of what we call the Threshold Standard, and it’s non-negotiable.
When it comes to materials, we stock eight premium brands, including Johns Manville, Owens Corning, and CertainTeed, plus specialty products like Reflectix for radiant barrier jobs. We match the material to the problem in your attic, not to whatever’s on the truck. And every job carries our 365-Day Done Right Promise in writing. If the repair fails within a year, we return and fix it free.
FAQs
In most San Antonio homes, open-cell spray foam can be applied directly over existing fiberglass in attic floor applications only if the batts are dry and undamaged. But we rarely recommend it. The fiberglass layer shifts over time and creates gaps that defeat the air seal the foam is supposed to create. For attic floors, we usually recommend removing the old batts and either re-blowing or spraying clean. For rooflines, the old batts come out entirely. Call (361) 213-9499 and we’ll tell you what your attic actually needs after we see it.
No. Spray foam installed to manufacturer specifications and local building code does not void a builder’s warranty. What sometimes causes friction is amateur installation that blocks soffit vents or traps moisture against framing. We install to code and to JM’s published application guidelines, and we document the installation with photos, so if your builder ever raises the question, you have a record. If you’re in a newer San Antonio subdivision with active builder warranties, that documentation matters.
Yes, in nearly every case. Johns Manville open-cell and closed-cell foams have distinct densities and cell structures, and we match partial repairs by product class, not just by color. Color matching is easy. Density matching is what restores the actual thermal and air-sealing performance. If the original product is no longer available, we tell you up front and recommend the closest performing equivalent instead of pretending a mismatch is an exact match.
Most spray foam estimates happen within 3 to 5 business days, and installation is typically scheduled within 5 to 10 business days after the written estimate. If you’ve got an active problem, like a roof deck that’s exposed or a room that’s uninhabitable, call us and we’ll tell you honestly whether we can prioritize it. We don’t promise same-week service we can’t deliver.
It depends on how much of the foam has failed and why. If a single bay has delaminated or a rim joist section pulled back, a spot repair is absolutely cheaper, often under $1,500. If the failure is widespread, caused by moisture, or the original install was thin everywhere, re-doing the area usually costs less in the long run than chasing individual failures year after year. We’ll show you the numbers and let you decide.
If you own a home in San Antonio with Johns Manville insulation and you’re not sure whether it’s doing its job, call (361) 213-9499. We’ll send someone who knows what they’re looking at, give you a straight answer, and put the price in writing before anything gets sprayed.
Written by Garrett Sloane, Owner, Aspen Attic Insulation San Antonio at Aspen Attic Insulation San Antonio, serving San Antonio and nearby areas.