Johns Manville Crawl Space Encapsulation Nationwide

Johns Manville Crawl Space Encapsulation: The Fort Worth Owner’s Guide

We stock and install Johns Manville crawl space encapsulation materials in Fort Worth, with most full encapsulation projects running between $4,800 and $9,500 depending on square footage, access height, and how much old vapor barrier needs pulling first. Same-day inspections are available, and we carry Johns Manville vapor barrier rolls, seam tape, and accessories on the truck. Most Fort Worth homeowners discover their encapsulation has failed after a heavy rain, when musty air starts drifting up through the floorboards or a humidity spike shows on the thermostat.

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The classic Fort Worth pattern: the original 6-mil poly installed by the builder ten years ago has torn along the edges, moisture is wicking through the concrete, and the fiberglass batts hanging in the floor joists are now damp and drooping. That’s the moment our phone rings.

Which Johns Manville Models This Applies To

Johns Manville doesn’t make “crawl space encapsulation kits” the way some brands sell an all-in-one box. They manufacture the individual components: FortiCell foam boards, perm-rated vapor barrier films, and their seam tapes. The most common setup we match in Fort Worth homes is a 10-mil or 12-mil Johns Manville reinforced poly laid over the dirt floor, run up the stem walls, and sealed with Johns Manville butyl seam tape at every overlap.

Here’s the compatibility gotcha we’ve learned over years of Fort Worth installs: the white Johns Manville vapor barrier film and the silver-backed roll are not interchangeable in hot, humid crawl spaces. The silver (multi-layer reflective) version is designed for walls and attics where radiant heat is the primary load. Put it on a damp Fort Worth crawlspace floor and the reflective layer delaminates from the poly within two to three Texas summers. We match the 10-mil white film to floors and the reflective rolls to the stem walls only. If you’re not sure which you have, look at the printed label along the roll edge, it lists the perm rating and intended application. We can identify it in about ninety seconds on a video call.

For OEM versus aftermarket: Johns Manville seam tape is genuinely better than generic butyl tape in high-moisture conditions. The adhesive holds below 50°F and doesn’t flag in standing condensation the way cheaper tapes do. We stock the OEM tape and use it. For the poly itself, a quality aftermarket 12-mil reinforced barrier often outperforms the standard 10-mil OEM film in Fort Worth’s freeze-thaw damp cycle, and we’ll quote you both options before any work begins.

Signs Your Johns Manville Crawl Space Encapsulation Is Failing

• Musty odor rising through the floor. When the vapor barrier tears or pulls away from the stem wall, ground moisture evaporates directly into the crawl space air. That humid air carries the smell of damp soil up through floor penetrations around plumbing and HVAC lines.
• Sagging or discolored floor insulation. Fiberglass batts hanging in the floor joists will soak up that evaporated moisture and start to droop. In Fort Worth’s clay-heavy soils, we see this happen fastest in neighborhoods built on tight clay that holds water for weeks after a storm.
• Condensation on ductwork or copper pipes in the crawl space. A failed encapsulation system means the crawl space breathes unconditioned outdoor air. During a Fort Worth summer, that’s 90°F air hitting 70°F supply ducts, and the sweating starts within days.
• Visible rips, missing seam tape, or barriers that have shifted off the stem walls. Rodents, plumbing repairs, and simple age all shred 6-mil and thinner films. Once water has a path, capillary action pulls moisture across the entire floor.
• Higher indoor humidity with no obvious AC fault. If the thermostat shows 60% plus relative humidity while the air conditioner runs normally, the source is almost always an open crawl space. Fort Worth’s summer air is humid enough that a failed barrier raises indoor humidity within one season.

Replacement Cost & What’s Included

Full crawl space encapsulation with Johns Manville materials in Fort Worth typically runs $4,800 to $9,500 installed. The range comes down to three things: crawl space square footage, access height, and how much failing material we have to remove before the new barrier goes down. A 1,200-square-foot crawl with easy access lands near the bottom of that range. A 2,500-square-foot space with two-foot clearance and twelve-year-old torn poly to pull out runs higher.

The written price you get from us includes the Johns Manville vapor barrier material, OEM seam tape, fastening to stem walls, removal of the old barrier, and a photo walkthrough before we leave. Every job carries the 365-Day Done Right Promise, which means if the seam separates or the barrier shifts within a year, we come back and make it right, no debate, no fine print. We don’t charge for estimates, and the number we quote is the number you pay.

DIY or Call Us?

Crawl space encapsulation is one of the few insulation jobs we genuinely recommend handing to a crew. It’s not that the materials are dangerous, the risk is doing the work incorrectly and not finding out for a year or more. A seam that’s taped but not cleaned properly will separate. A barrier that’s lapped six inches instead of twelve will leak at the overlap. And working in a low-clearance crawl space on your side, with a headlamp and a caulk gun, is slow, uncomfortable work that most Fort Worth homeowners rightly decide isn’t how they want to spend a weekend.

If you want to check your existing barrier before deciding anything, here’s what’s safe and useful: put on gloves and a mask, shine a light into the crawl space through the access door, and look for visible rips, standing water, or barrier that has fallen off the stem walls. Don’t crawl under the house without proper ventilation and a second person nearby. Once you’ve seen what’s there, call us at (682) 233-8300. We’ll inspect it properly, show you photos of what we find, and put a written number in your hands before any material comes off the truck.

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