Demilec Wall Insulation in San Marcos: What to Know First
We provide independent Demilec wall insulation service in San Marcos, typically completing jobs same-day or next-day once we’ve run diagnostics and delivered a written price. Most Demilec injection foam and drill-and-fill wall jobs in the San Marcos area run between $2,800 and $5,400 depending on wall cavity depth, existing foam condition, and whether the top plates need sealing first. We don’t start work until you have our written scope, our written price, and our written warranty in hand - that’s Haven Standard Clause 1. Call (737) 337-8049 if your Demilec walls are underperforming, settling, or were installed before the 2018 formulation changes.
How Demilec Products Fail - and How We Fix Them
- Demilec Heatlok HFO Pro shrinkage in 2×4 exterior walls. The early HFO Pro batches (pre-2019) installed in San Marcos homes can pull away from studs by 1/4 to 1/2 inch as they cure, creating convective loops that render the R-value meaningless. We remove the failed foam through 5/8-inch drill patterns, verify the cavity is dry with a moisture meter, then reinstall with current-spec open-cell or a hybrid closed-cell pack to the correct density.
- Demilec Sealection 500 density loss in soundproofing applications. Sealection 500 was marketed heavily for interior wall sound control in homes near the Texas State University corridor, but when it’s shot below 0.5 pounds per cubic foot it loses both its acoustic dampening and its structural adhesion. We test density with a core sample before quoting; if it’s low, we strip and repack at the proper 0.6 to 0.7 pcf spec.
- Demilec Heatlok XT off-ratio curing in humid cavities. San Marcos spring humidity can push wall cavity moisture above 19 percent, and Heatlok XT is unforgiving when the B-side isomer reacts with water vapor. The result is a crumbly, amber-tinted foam that smells like raw amine. We don’t cover it - we cut it out, dry the cavity with targeted airflow, then reapply only after a moisture meter reads below 16 percent for 48 hours.
- Demilec open-cell water absorption in slab-on-grade homes. In the older neighborhoods near Hutchison Street and the Rio Vista area, slab-on-grade construction with no capillary break means wicking moisture hits the bottom plate. Open-cell Demilec foam above it becomes a reservoir. We switch these cavities to closed-cell or install a vapor barrier at the stud bay bottom before repacking - never the same product in the same condition.
- Demilec retrofit injection foam degradation from UV exposure. When previous installers left the injection ports uncovered or drilled through to the exterior sheathing without sealing, Texas sun breaks down the foam surface. We find this most often on south and west walls in San Marcos homes built 2012 to 2017. Our fix: seal every penetration with a compatible caulk, then reinsulate with a UV-stable formulation.
Our Demilec Wall Insulation Process
- 1
Call and schedule. A live person answers 24/7. We book a diagnostic window and text you when the technician is en route - Haven Standard: Arrive on schedule, named technician, no mystery arrivals.
- 2
Blower-door test and thermal imaging. We pressurize the house to measure air leakage in CFM50, then run a FLIR scan to locate where your Demilec walls are bypassing air. The R-value tells you how slow heat moves through the material - the blower-door number tells you whether any of that matters.
- 3
Cavity inspection and written scope. We drill test ports, probe the existing foam with a borescope, and check moisture content. You get a written price, written scope, and written warranty before anyone lifts a tool. No exceptions.
- 4
Air sealing first, then insulation. Top plates, electrical penetrations, and can light boxes get sealed before any new Demilec or alternative product goes in. We learned this in Chicago winters and it matters just as much in San Marcos summers.
- 5
Installation and real-time verification. We install OEM Demilec or quality aftermarket equivalent - your choice, with the trade-offs explained - and verify pass thickness with a pin probe before the crew packs up.
- 6
Final blower-door test and documentation. We run the house again, print the before-and-after air-changes-per-hour on a single page, and add the photos to your Documented Photo Record. The 365-Day Done Right Promise starts now.
Before
AfterWhat Demilec Wall Insulation Costs in San Marcos
Most Demilec wall insulation jobs we handle in San Marcos fall in these ranges:
- Drill-and-fill injection foam, single-story 1,200 sq ft home: $2,800-$3,800
- Two-story with cavity stripping and repack, Heatlok HFO Pro replacement: $4,200-$5,400
- Interior soundproofing, Sealection 500 density correction, per wall: $1,800-$2,600
- Top-plate air sealing add-on (required if blower-door reads above 3,000 CFM50): $600-$900
What moves the price: cavity depth (2×4 vs. 2×6), whether we strip existing failed foam or inject around it, moisture remediation needs, and accessibility - balloon framing in pre-1980 San Marcos homes takes longer. We also source from Owens Corning, Johns Manville, Knauf, Rockwool, CertainTeed, Icynene, and GreenFiber if Demilec isn’t the right fit for your condition. Call (737) 337-8049 for a written estimate - they’re free, and we offer a Free Second Opinion on any competing quote you bring us.
Why San Marcos Homeowners Call Topside Attic Insulation San Marcos for Demilec Work
We’ve sealed and insulated over 9,000 homes since 2016, and the ones in San Marcos keep teaching us something. Wes Okafor, our owner, trained at Dawson Technical Institute in building science before two decades of diagnosing why attics and walls fail - not just filling them. On Demilec jobs, that means we know the difference between a formulation issue and an installation issue, and we won’t sell you new foam if the real problem is air moving around it. Every job gets the before-and-after blower-door number printed on one page. Every job gets the 365-Day Done Right Promise. And if Demilec isn’t available or isn’t right for your cavity condition, we carry Reflectix and other brands - no proprietary lock-in, no upsell pressure.
FAQs
Demilec’s product warranty covers manufacturing defects regardless of who installs it, but workmanship warranties from the original installer do not transfer. As an independent Demilec service provider, we cover our own installation with the 365-Day Done Right Promise and a written warranty you receive before work starts. Call (737) 337-8049 and we’ll review what coverage you have left.
Yes - Demilec Heatlok, Sealection, and APX lines remain available through regional distributors in Austin and San Antonio, with typical 48- to 72-hour lead time for specialty formulations. We also stock compatible aftermarket closed-cell and open-cell products if your job timeline doesn’t allow the wait. We explain the spec sheet differences before you choose.
Repair is cheaper when the foam is intact but underperforming due to air leakage around it - typically $600-$1,200 less than full cavity replacement. Strip-and-repack is necessary when the foam has degraded, shrunk, or absorbed moisture, because new foam bonded to failed foam will fail too. We determine which path after the borescope inspection and tell you honestly which one we’d choose for our own house.
Most single-story Demilec wall jobs finish in one day; two-story homes or jobs requiring cavity stripping need a second day. We schedule diagnostics within 48 hours of your call and stock common formulations locally. If your walls are open due to renovation or you’ve got a closing date, tell us - we’ll sequence around it.
You receive a written scope fulfillment checklist, before-and-after blower-door readings on one printed page, a Documented Photo Record of cavity conditions and completed work, and your written warranty. Haven Standard: Have it in writing. No handshake promises, no “trust us” - the numbers are either there or the job isn’t done.
Written by Wes Okafor, Owner, Topside Attic Insulation San Marcos at Topside Attic Insulation San Marcos, serving San Marcos and nearby areas.