Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The New Braunfels Owner’s Guide

Most Demilec attic air sealing jobs in New Braunfels run between $1,800 and $3,400 installed, depending on attic square footage and whether we’re sealing top plates, can lights, and duct chases or just the primary bypasses. We stock Demilec-compatible open-cell and closed-cell foam components, sealants, and vapor-retarder accessories on our trucks, and we can typically start the work same day we diagnose it. Homeowners usually discover a failure when their upstairs rooms won’t hold temperature despite new insulation, or when a blower-door test reveals the attic floor is still leaking at 3,000+ CFM50 after another contractor “finished” the job.

Call (830) 243-6352

Which Demilec Models This Applies To

Demilec’s product line for attic air sealing breaks into three categories we encounter in New Braunfels homes: the Heatlok HFO Pro series (closed-cell, 2.0 lbs/ft³ density, R-6.5 per inch), the Heatlok XT series (closed-cell with higher compressive strength for cathedral ceilings), and the Sealection 500 open-cell line (0.5 lbs/ft³, R-3.8 per inch, vapor-permeable). The part you need depends on what was originally specified for your assembly. Check the spray-foam surface for a Demilec lot label - usually a 2-inch by 3-inch sticker with a batch code starting in “HL” or “SS” - or measure the cured foam thickness and density with a simple pinch test. Open-cell feels spongy and rebounds; closed-cell feels rigid like a cooler lid.

We do not require OEM-only replacement. For most attic floor sealing in New Braunfels’s climate zone 2A, we can match Demilec’s performance spec with equivalent closed-cell foam from Icynene or Johns Manville where the original product is back-ordered, which has happened twice since 2022 with Heatlok HFO Pro reformulations. The key compatibility gotcha: if your original job used open-cell Sealection 500 on the roof deck for an unvented assembly, you cannot patch with closed-cell without trapping moisture. The vapor-profile has to match, or you’ll rot the sheathing. We verify this before quoting.

Topside Attic Insulation New Braunfels is an independent service provider. We are not affiliated with Demilec.

Signs Your Demilec Attic Air Sealing Is Failing

• Hot second-floor rooms in July despite the AC running flat-out. The thermal bypass is still open. In New Braunfels, where attic temperatures hit 140°F regularly, even a 5 percent gap in your air barrier lets superheated air wash down interior wall cavities through stack effect. The insulation above looks fine; the air is moving around it.
• Dust streaking on ceiling drywall near can lights or top plates. This is filtered leakage - conditioned air escapes into the attic, attic air replaces it through every crack, and the drywall acts as a filter. We see this pattern most in Canyon Lake area homes built 2005-2015 where the original contractor skipped sealing around plastic J-boxes.
• Ice damming or heavy frost on roof sheathing in winter. Warm, moist interior air hits cold plywood and condenses. In New Braunfels this is less common than up north, but we caught three cases last winter in homes with unvented attics where the Demilec open-cell had pulled away from the deck at the ridge.
• Blower-door test shows minimal improvement after “air sealing” by another contractor. We tested a home off River Road last March where a handyman had run a bead of caulk around the attic hatch and called it sealed. The CFM50 dropped from 4,100 to 3,800 - essentially noise. Proper top-plate and penetration sealing dropped it to 2,100.
• Musty odor from HVAC returns after rain. Air leakage paths often connect attic cavities to soffits or wall chases that get damp. The Demilec foam itself doesn’t fail, but if it was applied over dusty, oily framing or in too thin a pass, the bond breaks and the path reopens.

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Replacement Cost & What’s Included

Every quote is flat-priced under Haven Standard Clause 1: written scope, written warranty, no add-ons after we start. The price includes material, labor, before-and-after blower-door testing, and your Documented Photo Record. We warranty the seal quality for 365 days under our Done Right Promise - if the CFM50 doesn’t hit the target we wrote down, we return and fix it.

DIY or Call Us?

Here’s what you can safely check yourself: look at the attic hatch - is it weatherstripped and does it sit flat? Are can lights covered with sealed boxes, or are they open to the attic? These are visual, no-tools checks. If you find gaps, mark them with masking tape and take photos.

Here’s where DIY goes wrong: Demilec closed-cell foam requires professional-grade plural-component equipment heated to 110-120°F with precise A-side/B-side ratio control. Off-the-shelf canned foam shrinks, cracks, and creates a fire hazard if used around hot fixtures. Open-cell requires similar equipment at different pressures. More critically, you cannot verify your own work without a blower-door test - a pressurization diagnostic that measures how many cubic feet of conditioned air your house leaks per minute. We’ve found $80 worth of canned foam jobs that actually increased leakage by compressing existing fiberglass and opening new bypasses. The number on the blower-door printout tells you what the insulation did. Everything else is just talk.

Call (830) 243-6352 and we’ll run the test first. Estimates are free, and we publish the numbers whether you hire us or not.

FAQs