Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Menlo Park Owner’s Guide

Demilec-compatible attic air sealing installed in Menlo Park typically runs $1,800-$3,400 for a complete top-plate and penetration seal on a 1,200-2,400 sq ft home, and we stock the full Demilec component line for same-day starts. Most homeowners discover the problem when their upstairs rooms won’t hold temperature despite new insulation, or when a recent energy audit flags thermal bypass at the attic floor. The fix isn’t more insulation - it’s sealing the leaks that render existing insulation useless.

Call (510) 876-4113

“Seal the leaks first. The insulation has nowhere useful to go until you do.”

Which Demilec Models This Applies To

Demilec produces several air-sealing chemistries under the Heatlok and Sealection brands, and the part you need depends on when your system was installed and what substrate it bonds to. Heatlok HFO Pro, Heatlok XT, and Sealection 500 are the three series we encounter most in Menlo Park attics, particularly in homes built between 1960 and 1995 where top plates and wire penetrations were never originally sealed.

To identify your Demilec component, look for the spray-foam canister label or the cured-foam stamp left by the original installer - usually found on the attic floor joists or rim joist. Heatlok HFO Pro uses a closed-cell formulation rated at R-6.5 per inch and requires a specific A-side/B-side ratio; Sealection 500 is an open-cell product at R-3.7 per inch with different expansion characteristics. Mixing the two during repair work creates adhesion failure within 18 months. We carry OEM Demilec cartridges and the compatible gun-cleaning solvents, plus aftermarket equivalents from Icynene and Johns Manville where the substrate condition warrants a chemistry switch. Topside Attic Insulation Menlo Park is an independent service provider - not affiliated with Demilec - and we select the sealant based on what your attic actually needs, not brand loyalty.

Signs Your Demilec Attic Air Sealing Is Failing

• Dust streaks on ceiling insulation. Air moving through gaps in the Demilec seal carries attic dust into the insulation batts, leaving dark trails that look like water damage but indicate active bypass. The seal has cracked or pulled away from the top plate.
• Hot second-floor rooms in July despite running AC continuously. Conditioned air escapes through unsealed penetrations faster than your cooling system can replace it. In Menlo Park’s summer pattern, attic temperatures hit 130°F and the thermal drive intensifies every leak.
• Ice damming at the eaves in rare freeze events. Warm attic air melts roof snow unevenly; the refreeze at the overhang dams water back under shingles. This points to air leakage at the attic floor, not inadequate insulation depth.
• Blower-door test shows minimal improvement after insulation upgrade. A contractor blew cellulose over unsealed gaps. The Demilec air seal was never installed or failed prematurely, so your ACH50 barely moved despite the new R-value.
• Can lights that drip condensation in winter. Humid interior air finds a path around failed Demilec seals near recessed housings, condensing on cold fixture surfaces. This is a fire-safety issue as much as an efficiency problem.

Before

After

Replacement Cost & What’s Included

The range depends on attic accessibility, existing insulation that must be moved and replaced, and how many penetrations need individual treatment. Every job includes: written scope and fixed price before work starts (Haven Standard Clause 1), pre- and post-blower-door testing with printed ACH50 readings, and a Documented Photo Record showing each sealed penetration. We also stock Reflectix radiant barrier components where the attic configuration benefits from combined air-sealing and heat-reflective work. The 365-Day Done Right Promise covers adhesion failure, shrinkage, or missed gaps.

DIY or Call Us?

There’s a short list of what a homeowner can safely verify: check for visible gaps around the attic hatch, feel for temperature differences with the back of your hand near can lights, and look for the dust-streak pattern on insulation. Do not attempt to apply or repair Demilec two-component foam yourself. The A-side isocyanate requires respirator protection with organic vapor cartridges, the substrate must be conditioned to manufacturer temperature specs, and the expansion ratio varies by chemistry - Heatlok HFO Pro expands 8:1, Sealection 500 expands 120:1. Misapplication fills wall cavities, warps drywall, and creates off-gassing that persists for weeks.

We carry the full Demilec component inventory on our trucks, so most Menlo Park jobs start the same day you call. Wes Okafor runs every initial assessment personally - he’ll walk your attic with a smoke pencil, show you where the air is moving, and hand you a written price before anyone schedules work. Call (510) 876-4113.

FAQs