Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Boerne Owner’s Guide

We stock and install Demilec-compatible attic air sealing components for Boerne homes, with most residential jobs running between $340 and $780 installed depending on attic square footage and penetration count. Same-day service is available when you call before noon, and we carry the common Demilec gasket sets, foam applicator tips, and cured-foam removal tools on every truck. Most Boerne homeowners discover their Demilec air sealing has failed when rooms stay stubbornly warm despite the AC running, or when they spot dusty insulation patterns near can lights and top plates - the telltale sign that conditioned air is escaping through gaps the original sealant no longer closes.

Call (830) 529-7780

Which Demilec Models This Applies To

Demilec’s attic air sealing line breaks into three series you’re likely to encounter in Boerne’s 2005-2022 build stock: the SEALEZE residential gasket system, the FOAM-LOK spray foam perimeter kits, and the older AIRSTOP tape-and-membrane assemblies found in many Hill Country custom builds from the 2010s. The SEALEZE gaskets carry a yellow label with a 12-digit part code starting in DM-SE; FOAM-LOK applicator sets have a blue label and a batch date you need to check, because Demilec reformulated the catalyst in 2019 and pre-reformulation foam can become brittle in Texas heat cycles after roughly six years.

To identify what you need, measure the gap width at your attic’s top plates - SEALEZE comes in 3/8-inch, 1/2-inch, and 5/8-inch compression profiles, and ordering the wrong profile means the gasket won’t seat under the drywall edge. We stock all three on our Boerne trucks. For the OEM-versus-aftermarket question: Demilec’s own gaskets hold up well, but we also carry a Johns Manville equivalent that meets the same ASTM C834 spec at a lower parts cost. We will show you both and explain the warranty difference before you decide. Topside Attic Insulation Boerne is an independent service provider - not affiliated with Demilec - so we have no incentive to push one brand over another.

Signs Your Demilec Attic Air Sealing Is Failing

• Uneven room temperatures upstairs. When the SEALEZE gasket compresses permanently or the FOAM-LOK bead shrinks, conditioned air bleeds into the attic through top plate gaps. The master bedroom ends up 8 degrees warmer than the hallway because that chase sits directly under a failed seal line.
• Dust streaks on insulation near can lights or wire penetrations. This is filtration soiling - attic air being pulled through the gap carries dust that deposits on the insulation surface like a coffee stain. In Boerne, we see this most often on north-facing attic slopes where temperature differentials stay high longest.
• HVAC running longer than it used to for the same outdoor temperature. Your system isn’t broken; it’s chasing air that leaves faster than the thermostat can sense the loss. We have measured blower-door numbers in Boerne homes where failed attic sealing alone accounted for 1,200 CFM50 of excess leakage.
• Ice damming or moisture staining at ceiling corners in winter. When warm, humid indoor air hits cold attic framing through a gap, condensation forms on the drywall. Demilec’s AIRSTOP membrane was particularly prone to corner lifting if the substrate wasn’t primed - a shortcut we find in about 30 percent of the older Hill Country homes we inspect.
• New insulation performing below expectation. This is the one that stings. A homeowner in The Heights at Tapatio Springs had R-38 blown in last year and saw no bill reduction. We found the original FOAM-LOK bead cracked and pulling away from the top plates. Seal the envelope first. Then fill it. The insulation was doing its job; the air sealing had quit.

Replacement Cost & What’s Included

The range depends on three factors: how much existing Demilec material needs removal (cured FOAM-LOK takes longer to cut out than gasket), whether we need to build a baffle or dam at the eaves to maintain vent channel clearance, and how many penetrations your particular attic carries - a 2018 build with recessed LEDs and a central vac chase has more leak points than a 1995 home with surface-mounted fixtures. Every quote is a flat, written price before any work starts, per Haven Standard Clause 1. The parts carry a 5-year material warranty; our labor is covered by the 365-Day Done Right Promise. You also get a Documented Photo Record of every sealed penetration and, on full jobs, printed before-and-after blower-door numbers in pascals.

DIY or Call Us?

Here’s what you can safely check yourself: turn off your attic lights during daylight and look for pinholes of light around can light housings, or feel for temperature differences with your hand near top plates on a hot afternoon. What you should not do is attempt to remove cured spray foam or apply new FOAM-LOK without proper respiratory protection and ventilation. The isocyanate component in two-part foam is a sensitizer - once you’re sensitized, you can’t work around it again, and attic air changes are easy to underestimate.

We also see DIY gasket installs where the homeowner used the wrong compression profile and created a new gap rather than closing the old one. If you want to handle the diagnosis yourself, fine - but for the remediation, call (830) 529-7780. We will give you a written price on-site, and if you have a competing quote, we will read it with you under our Free Second Opinion policy.

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