Johns Manville Attic Insulation: The San Antonio Owner’s Guide
If you’re looking for Johns Manville attic insulation in San Antonio, we install it and we stock it. A typical Johns Manville blown-in fiberglass or batt insulation job runs $900 to $2,400 installed depending on square footage and the R-value you need, and most single-attic projects are finished same day. You’ll know your current insulation has failed when your upstairs rooms won’t hold temperature, your AC runs constantly from May through October, or you can see bare joists poking through thin, settled material when you peek into the attic.
Johns Manville has been making insulation since 1858, and their attic products show up in a lot of San Antonio homes built from the 1990s onward. The most common thing we hear from homeowners is that their JM insulation was decent when it went in but has since compacted, gotten wet from a roof leak, or was never deep enough for a Texas attic in the first place. We’ll get into exactly what fails and what it costs to fix below.
Which Johns Manville Models This Applies To
Johns Manville sells attic insulation under a few main product lines, and they’re not all interchangeable. The big three we see in San Antonio attics are ComfortTherm (faced batts with a plastic vapor barrier wrap), Attic Protector (blown-in loose-fill fiberglass), and Climate Pro (blow-in fiberglass sold through big-box stores). ComfortTherm batts come pre-cut in 15- and 23-inch widths for standard joist spacing, while Attic Protector and Climate Pro are loose-fill products you blow in with a machine to whatever depth your R-value target requires.
Here’s the compatibility gotcha: you can’t just drop any JM product into any attic and call it done. If your attic has existing batt insulation between the joists, the right move is usually to top it with blown-in fiberglass rather than layering more batts, because batt-over-batt creates gaps and compresses what’s underneath. If your attic has old blown-in cellulose or rock wool, we typically remove it first so the new Johns Manville material lays evenly. And if your HVAC ducts run through the attic, you want to raise the insulation to the roofline in some cases, which changes the product spec entirely. As an independent San Antonio insulation contractor, we’re not tied to Johns Manville corporate, so we’ll tell you honestly when a JM product is the right call and when Rockwool or CertainTeed would serve that specific attic better.
Signs Your Johns Manville Attic Insulation Is Failing
- Your upstairs rooms run 8 to 12 degrees warmer than downstairs in summer. In San Antonio’s July heat, the sun beats on your roof until the attic hits 140°F or higher. Insulation that’s settled or too thin lets that heat radiate straight through the ceiling drywall.
- You can see the tops of your ceiling joists from the attic access. If the insulation doesn’t cover the joists completely, you’re running at roughly R-11 to R-19 at best. San Antonio’s climate zone 2 wants R-38 to R-49 in most homes.
- Your energy bill jumped without a change in usage. CPS Energy rates have gone up, but a $40 to $80 monthly spike with no new appliance or behavior change usually points to insulation that’s no longer doing its job.
- You find damp or darkened insulation near the eaves or under roof penetrations. Wet fiberglass loses nearly all insulating value and can grow mold in the Texas humidity. That material needs removal, not a top-up.
- Rodents or raccoons have been in the attic. Pests tunnel through fiberglass, mat it down, and leave droppings that make the space unhealthy. We see this constantly in older San Antonio neighborhoods like Jefferson and Monticello Park.
Replacement Cost & What’s Included
For a standard San Antonio single-story home with an attic around 1,200 to 1,500 square feet, installing new Johns Manville Attic Protector blown-in fiberglass to R-38 typically lands between $1,100 and $1,900. R-49 upgrades for bigger homes or added efficiency run $1,800 to $2,400. If we’re removing old insulation first, add $600 to $1,200 depending on how much material and debris are up there. Those numbers include labor, material, and cleanup.
What determines the final price is attic square footage, target R-value, access difficulty, and whether old insulation needs to come out first. You get a written price before we start, every time, no exceptions. And every Johns Manville install we do in San Antonio carries our 365-Day Done Right Promise: if the insulation settles, gaps form, or anything isn’t right within a full year, we come back and make it right in writing. No charge, no argument.
DIY or Call Us?
You can absolutely check your attic yourself with a flashlight and a tape measure. Look for bare joists, measure the depth of what’s there, and feel for damp spots near roof penetrations. That inspection tells you whether you have a problem. What it won’t tell you is how to fix it correctly. Blowing in fiberglass requires a machine, proper PPE (fiberglass particles in your lungs are no joke), and an understanding of air sealing, baffles, and ventilation that most homeowners just don’t have. Plus, if your attic has knob-and-tube wiring or old recessed lights, burying them in insulation is a fire hazard unless handled properly.
We’ve also seen DIY jobs where homeowners blocked soffit vents with insulation and turned their attic into a mold farm within one Texas summer. So yes, check it yourself. But if the insulation is shot, call (254) 279-0971 and let us handle the heavy, itchy, technically specific part.
FAQs
Fiberglass insulation itself never really degrades, but in San Antonio’s heat and humidity, blown-in fiberglass can settle and lose up to 20% of its R-value over 15 to 20 years, especially if it was installed too shallow from the start. If your home was built before 2005 and the attic hasn’t been touched since, it’s worth a check.
In many cases, yes. If the existing material is dry, mold-free, and just too thin, we can top it with new Johns Manville blown-in fiberglass to bring it up to R-38 or R-49. If there’s moisture damage, pest contamination, or significant settling, replacement is the honest call. Call us at (254) 279-0971 for a free attic assessment and we’ll tell you which path your insulation actually needs.
Most San Antonio attics are done in 4 to 6 hours, same day. Removal of old insulation adds 2 to 3 hours. We’ll give you a live arrival time before we show up, so you’re not sitting around waiting on a four-hour window.
Yes. We keep Johns Manville batts and blown-in fiberglass on the truck, and we also stock Reflectix for radiant barrier applications. If your job calls for a different brand, we carry seven others, including Owens Corning, Rockwool, and CertainTeed.
Call Laurel Attic Insulation San Antonio
If you’ve got a San Antonio attic with failing Johns Manville insulation, call us at (254) 279-0971 for a free estimate. You’ll get a live person on the phone, a written price before any work starts, and a crew that shows up when they say they will. A comfortable attic isn’t a luxury in San Antonio, it’s just a house that works the way it should.
Written by Chase Whitaker, Owner, Laurel Attic Insulation San Antonio at Laurel Attic Insulation San Antonio, serving San Antonio and nearby areas.