Demilec Crawl Space Encapsulation: The Houston Owner’s Guide
We install and service Demilec-compatible crawl space encapsulation systems across Houston, with most complete encapsulation jobs running $4,200 – $9,800 depending on square footage, access height, and the condition of your existing vapor barrier. Same-week scheduling is typically available, and we stock Demilec Heatlok HFO and Sealection 500 on our trucks for repair work. Most Houston homeowners discover a failing encapsulation not by looking for it, but by walking into a house that smells like a musty basement after a heavy rain, or by pulling up the floor register and catching a whiff of damp earth.
If you’ve got a Demilec foam product in your crawl space and something isn’t holding up, here’s what you need to know before you spend a dollar.
Key takeaways:
- Demilec closed-cell foams (Heatlok HFO, Sealection 500) are the standard for Houston crawl spaces because they handle humidity without sagging.
- Most “failed” Demilec installations fail at the seams and terminations, not in the foam itself.
- We’re an independent Houston insulation contractor. We install and repair Demilec products, but we’re not affiliated with Demilec or its parent company.
- Every repair or install gets a written price before work starts and a 365-day written guarantee.
Which Demilec Models This Applies To
Demilec makes a range of spray foam products, but in Houston crawl spaces we almost always see two: Heatlok HFO, a closed-cell foam typically applied at 2 inches for a Class II vapor retarder plus air barrier, and Sealection 500, an open-cell foam used more for sound and air sealing in conditioned crawl spaces. Heatlok HFO Pro is the newer formulation with lower global warming potential, and it’s fully backward-compatible with older Heatlok HFO jobs when it comes to repair overlap.
If you don’t know which Demilec product you have, check the access door or the top of the foundation stem wall. The installer should have left a small label or stencil mark, but in many resale homes that label is long gone. We can identify the foam by appearance and density on site: closed-cell Heatlok is rigid and smooth with a slightly waxy feel, while open-cell Sealection looks like a dense sponge and you can press a finger into it. That identification matters because you can’t patch open-cell with closed-cell and expect the same vapor performance.
One compatibility note that trips up a lot of Houston homeowners: the Demilec warranty and code approval assume the crawl space was prepped correctly. If the original installer sprayed over standing water, left 3-foot gaps at the soil, or skipped the termite inspection gap at the sill plate, the foam itself might be fine while the system fails. We evaluate the whole encapsulation, not just the foam.
Signs Your Demilec Crawl Space Encapsulation Is Failing
- Musty or earthy smell inside the house after rain. This is the first and most common signal. It means ground moisture is getting past the vapor barrier and rising into the floor assembly. A properly sealed Demilec crawl space should keep that smell out entirely.
- Sagging or torn vapor barrier on the crawl space floor. In Houston’s gumbo clay soil, water moves sideways after heavy rain and can push up under a 6-mil barrier that wasn’t overlapped and taped correctly. Once the barrier tears, it’s no longer doing its job, no matter how good the wall foam is.
- Foam pulling away from the block or stem wall. This happens when the wall wasn’t dry at spray time, or when groundwater pressure behind the wall pushes hydrostatic moisture through. You’ll see a gap at the top or bottom edge of the foam, and that gap breaks the air and vapor seal.
- Condensation on ductwork or floor joists in the crawl space. This is a sign humid Houston air is still entering the space. In a properly encapsulated crawl space with a functioning Demilec barrier, the dew point stays below the surface temperature of the joists. When you see sweating ducts, the seal has failed somewhere.
- Higher summer cooling bills that don’t match the thermostat setting. A failed encapsulation lets humid air into the floor system, and humid air costs more to cool than dry air. If your bill climbs through a Houston summer and the AC is running fine, the crawl space is usually where the leak is.
Replacement Cost & What’s Included
For a typical 1,200 – 1,800 square foot Houston crawl space, a full Demilec-compatible re-encapsulation runs $4,200 – $6,800. Larger homes, tighter access (under 30 inches of clearance), and spaces with previous standing water push that to $7,500 – $9,800. A partial repair, like re-foaming a failed wall section or replacing a torn floor barrier, usually lands between $900 and $2,400.
Every quote includes the foam or barrier material, the labor to remove and dispose of failed material, prep work on the walls and floor, and a written 365-day guarantee under the 365-Day Done Right Promise. If the repair fails in that window, we come back free of charge. The written price you approve before we start is the price on the invoice. No adjustments at the door.
We also stock Reflectix radiant barrier products for Houston homes that choose a supplemental heat-block layer along the floor joists, but the core moisture work is done with Demilec foam and reinforced vapor barrier.
DIY or Call Us?
You can safely inspect your own crawl space, and we recommend doing that once a season in Houston. Check for standing water, missing barrier overlaps, torn floor liner, and foam that has visibly separated from the wall. Those are all things you can see with a flashlight and a phone camera without touching anything.
What you shouldn’t do is attempt to re-spray or patch Demilec foam yourself. Closed-cell spray foam requires proper surface temperature, substrate dryness, and precise mixing ratios, and getting it wrong can mean a patch that never cures correctly or that off-gasses inside your house for weeks. The foam also adheres to skin and eyes and removal requires mechanical scraping. That work belongs to a trained crew with the right respirators and equipment. If your seam tape has failed on the floor barrier, that’s also a job where bad tape and poor overlap means you paid for a material you’ll replace inside a year.
If you’re unsure what you’re looking at, call (806) 581-1010 and we’ll talk you through it. If a visit makes sense, the estimate is free.
How We Work at Alden Insulation Houston
Alden Insulation Houston is independently owned and operated, held to The Garrison Standard under the Garrison Partners family, which has been setting the bar since 2002. Every technician who steps onto your property is background-checked and in uniform, and every call is answered by a live person, 24/7. We carry Demilec, Owens Corning, Johns Manville, Knauf, Rockwool, CertainTeed, Icynene, and GreenFiber products, so when you research what’s going into your crawl space, you’re looking at names you can verify yourself.
Bryce Holloway oversees our Houston crews. He spent years learning building science before turning it into a career, and he’s been running jobs across Houston, including deep in Meyerland where slab homes and humid summers make a tight thermal envelope essential. Bryce reads a crawl space the way a mechanic reads an engine: methodically, checking every penetration and every seam before giving you a number. Good insulation doesn’t announce itself, you notice it on your utility bill.
FAQs
Properly installed Heatlok HFO closed-cell foam can last 30+ years in a Houston crawl space, and the vapor barrier floor liner typically lasts 15 – 20 years before Houston’s soil moisture and seasonal movement degrade it. The weak points are always the taped seams, the soil contact edges, and the termite inspection gap, which is why we inspect those first on every service call. Call (806) 581-1010 if your current encapsulation is under 10 years old and showing signs of failure.
Yes, in most cases we can remove the failed section, re-prep the substrate, and re-spray with Demilec product to restore the air and vapor seal without redoing the entire crawl space. The repair is only as good as the surrounding material, though, so if the foam was applied too thin or to a wet wall originally, a full re-application is the honest fix. Estimates are free either way.
A full re-encapsulation on a typical Houston home takes 1 – 2 working days, with the foam spraying done in one day and the barrier work and seam sealing on the second. A partial foam repair usually runs 4 – 6 hours from start to cured. We schedule inside a specific arrival window, not a vague half-day range.
We keep Heatlok HFO and Sealection 500 in stock on our Houston service trucks, along with reinforced vapor barrier, seam tape, and the prep materials needed for same-day repair work. That means most service calls don’t need a follow-up visit just to bring the right material. Call (806) 581-1010 and we can tell you over the phone whether your repair is one we can handle the day we arrive.
Ready to Fix Your Crawl Space?
Call Alden Insulation Houston at (806) 581-1010 for a free estimate on Demilec crawl space encapsulation repair or replacement in Houston. You’ll get a written price before any work starts, a straight answer on what’s failing, and a 365-day written guarantee on the work. No voicemail, no forms, no callbacks at the door with a different number.
Written by Bryce Holloway, Owner, Alden Insulation Houston at Alden Insulation Houston, serving Houston and nearby areas.