Johns Manville Crawl Space Encapsulation & Vapor Barrier in Chicago: What to Know First
We provide independent Johns Manville crawl space encapsulation and vapor barrier work across Chicago, and most jobs go from first call to finished install in two to three days. A full encapsulation in a Chicago crawl space, including a Johns Manville-compatible vapor barrier, typically runs between $4,800 and $11,000 depending on square footage, access, and how much old material needs to come out first. We publish the written price before any work starts, per Haven Standard Clause 1.
This page is for homeowners in Chicago who already have Johns Manville insulation or vapor barrier products in their crawl space, or who are considering them, and want a contractor that knows how those specific materials behave in a Chicago foundation climate. If you’ve got moisture, mold, or failed Johns Manville material under your house, call (218) 261-7714 and you’ll get a live person, not a voicemail tree.
How Johns Manville Products Fail - and How We Fix Them
- Johns Manville ComfortTherm vapor barrier tears and sags. The ComfortTherm line ships with a white vinyl facing that gets brittle after years of Chicago temperature swings, especially in vented crawl spaces where winter air drops into the 20s. Once the facing cracks, the batts absorb moisture and lose R-value fast. We remove the failed batts, address the moisture source first, and only then install new material.
- Johns Manville AP Foil-Faced polyiso absorbs water at cut edges. In Chicago crawl spaces, polyiso boards cut to fit around piers and plumbing lines expose the fiber core. That core wicks water like a sponge, which is why we see delaminated foil faces and swollen edges on JM board in damp crawl spaces. The fix is not another board in the same spot. It’s sealing the ground and rim joists first, then reinstalling with taped and sealed edges.
- Johns Manville MR Faced batts lose their kraft facing to humidity. The asphalt-based kraft facing on MR batts degrades when a Chicago crawl space runs above 60% relative humidity for months at a time. The facing peels away, and the fiberglass underneath sags. We find this on batches installed before encapsulation became common here. We pull the old batts, encapsulate, and re-insulate against a dry substrate so the new facing stays put.
- Vapor barrier seams fail at pier and column penetrations. Whether it’s a 6-mil poly or a heavier reinforced barrier, the seams around concrete piers and steel columns are the first places ground moisture gets through in Chicago’s clay-heavy soil. We terminate and seal every penetration mechanically, not just with tape, and we document each termination with photos before covering anything.
- Condensation collects on the underside of JM insulation installed against unsealed rim joists. This is the failure mode we see most in Chicago crawl spaces: fiberglass or foam board installed against rim joists that were never air sealed. Warm air from the house hits the cold rim board, moisture condenses, and the insulation holds that water against the wood. The fix is air sealing the rim joist bays first with closed-cell foam or sealed rigid board, then insulating. Insulation over an unsealed rim joist is the crawl space equivalent of leaving a window open all January.
Our Johns Manville Crawl Space Encapsulation & Vapor Barrier Process
- 1
Site walk and written scope. We measure the crawl space, map the moisture sources, and check what JM material is currently in place. You get a flat written price before anything gets removed.
- 2
Ground prep and cleanout. We remove failed insulation, old vapor barrier, and any debris - including rodent droppings where present - so we’re working against a clean floor.
- 3
Air sealing at the rim joists and penetrations. This is the step most Chicago crawl space contractors skip. We seal rim joist bays, plumbing penetrations, and any chase openings before any barrier or insulation goes in. This is the “seal the holes first” thinking that started Topside Attic Insulation
- 4
Vapor barrier install. A 10-mil or thicker reinforced barrier goes down wall to wall, lapped at seams by at least 12 inches and mechanically terminated at piers, columns, and the foundation wall. We tape and seal joints, then run the barrier up the wall and secure it.
- 5
Drainage and dehumidification review. If the crawl space needs a perimeter drain, sump pump, or dehumidifier to actually hold the moisture target, we’ll include it in the same scope rather than coming back later. We don’t encapsulate a crawl space that’s actively taking on liquid water and call it done.
- 6
Documentation. Before and after photos, the installed material types and R-values, and moisture readings are all in the printed report you get when we leave. If you want it, we can run a pre and post encapsulation humidity log over several days to show the dry-out curve.
What Johns Manville Crawl Space Encapsulation & Vapor Barrier Costs in Chicago
Here are the ranges we see across Chicago for Johns Manville-related crawl space work. These are written, flat prices - not estimates that move after the first cut.
- Vapor barrier only, 800-1,200 sq ft crawl space: $2,800-$4,500
- Full encapsulation with rim joist air sealing: $5,500-$8,500
- Encapsulation plus JM batt or board insulation replacement: $7,000-$11,000
- Cleanout of failed JM insulation plus encapsulation: Add $800-$1,600 depending on access and disposal volume
What moves the price in Chicago: crawl depth (anything under 36 inches slows the crew and adds labor), column and pier density in older bungalows and two-flats, and whether the existing JM material has been wet long enough to need full removal. A 900-square-foot crawl space in Portage Park with clear access will land on the low end. The same square footage in a 1920s Jefferson Park frame house with 24-inch clearance and pier work will land higher. Call (218) 261-7714, we’ll give you a written number before anything starts.
Why Chicago Homeowners Call Topside Attic Insulation for Johns Manville Work
We’ve sealed and insulated 9,000+ homes since 2016, and every one of them got a written price before work started and a documented photo record when the crew left. That’s the Haven Standard, and it applies the same way to a 700-square-foot crawl space as it does to a full attic. We’re not a Johns Manville authorized contractor, and we don’t pretend to be. What we are is an independent Johns Manville service provider that’s worked with JM batts, board, and vapor barrier products in Chicago crawl spaces long enough to know exactly how they fail here. If a job calls for a different material - Reflectix radiant barrier in a specific spot, or a different brand of board because the supply chain or the spec demands it - we use what fits the building science, not what’s easiest to stock. One phone call, a live person, and a written price. That’s the whole model.
FAQs
No. Once Johns Manville fiberglass or polyiso board has been saturated - especially ComfortTherm batts with vinyl facing that traps water - the R-value drops and won’t recover by drying alone. Batts mat down and lose loft; board delaminates. We remove and replace it. If the moisture was caught early and the material is dry, we’ll tell you that too, and you keep it. Call (218) 261-7714 and we’ll tell you what we’d actually do under your house.
In most cases, yes. We source Johns Manville ComfortTherm, MR Faced, and AP Foil-Faced polyiso through local Chicago supply houses, and we’re not locked into any single brand, so if a specific JM product isn’t available or the job would be better served by another manufacturer, you get that written into the scope with the price attached. Call (218) 261-7714 for a written scope.
For a tear or pulled seam in a barrier that’s otherwise intact, a targeted repair runs $300 to $700 in most Chicago crawl spaces. For a barrier that’s been down 10+ years, is torn in multiple spots, or wasn’t properly sealed at piers and columns, full replacement with mechanical terminations is usually the more durable play. We’ll give you both prices in writing and you decide. No pressure, no urgency, just numbers.
Usually, yes. We run crews across Chicago and the inner suburbs five days a week, and we schedule crawl space inspections with a named technician and a text when they’re on the way. Call (218) 261-7714 and we’ll get you on the calendar.
We can’t speak for manufacturer warranty terms, but as an independent Johns Manville service provider, we install to the manufacturer’s published specs and document everything with photos and a written scope. If you have a warranty question, bring us the paperwork and we’ll read it with you before any work starts. Free second opinion, written.
Seal the holes first. Then add the R-value. The numbers will tell you whether it worked. That’s how we run every crawl space job in Chicago, Johns Manville or otherwise.
Written by Wes Okafor, Owner & Lead Building Envelope Technician, Topside Attic Insulation at Topside Attic Insulation, serving Chicago and nearby areas.