Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Pasadena Owner’s Guide

Demilec-compatible attic air sealing installed in Pasadena typically runs $1,800-$3,400 for a complete top-plate and penetration seal on a 1,200-2,200 square foot home, and we stock the full Demilec foam and accessory line for same-day starts when you call (213) 816-5351. Most homeowners realize their Demilec air sealing has failed when rooms stay unevenly warm through a Pasadena September afternoon despite the AC running, or when their summer electric bill jumps 20-40% year-over-year with no rate change. The foam cracks, pulls away from framing, or was applied thin at the eaves to begin with, and conditioned air escapes into the attic exactly where it was supposed to be stopped.

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Which Demilec Models This Applies To

Demilec’s attic air sealing products fall into two main families you’re likely to find in Pasadena homes: the Heatlok Soya closed-cell spray foam line and the Sealection 500 open-cell system, both marketed heavily to California contractors during the 2016-2022 Title 24 code push. The Heatlok series cures to a rigid, yellow-tan foam rated at R-6 per inch and was commonly used for rim joists and top plates in newer builds around Chapman Woods and the Madison Heights area. Sealection 500, gray when cured and softer to the touch, was the go-to for filling irregular joist bays and wire penetrations in the pre-1940s bungalows near Bungalow Heaven where framing isn’t square.

To identify what you have, check the cured foam color and density. Heatlok is rigid enough that you cannot press a fingernail into it; Sealection indents slightly. If the original installer left a data tag, Demilec batch numbers start with HS- for Heatlok or SS- for Sealection, followed by a six-digit date code. We carry both OEM Demilec formulations and equivalent-density aftermarket foams from Icynene and Johns Manville that match the thermal performance specs without the brand premium. For Pasadena’s combination of dry heat and occasional winter moisture, we generally recommend staying with the original density class, open or closed, because switching densities without adjusting the vapor profile can create condensation issues at the roof deck.

Signs Your Demilec Attic Air Sealing Is Failing

• Hot second-floor rooms in late afternoon. The foam at the top plates has pulled away from the wall framing or shrunk, creating a direct channel for attic air, which hits 140°F in a Pasadena August, to drop into your conditioned space through the stud bays.
• Dust streaks around ceiling registers or can lights. This means air is moving the wrong direction through the envelope, pulled by pressure imbalances. The Demilec seal around duct boots or electrical boxes has cracked or was never complete at installation.
• Ice damming or moisture staining at the eaves in winter. Even Pasadena gets enough January chill for this. Warm, moist interior air bypasses the failed seal, condenses on the underside of the roof deck, and the water runs down to the eave where it soaks insulation.
• Blown-in insulation that has settled into a gray, dirty crust near the attic hatch. That’s filtration soiling, airborne dust from your living space getting pulled through gaps the Demilec was supposed to close, then trapped in the cellulose or fiberglass above.
• Your HVAC runs noticeably longer than neighbors with similar homes. We see this complaint constantly from the 1950s ranch homes south of Colorado Boulevard. The system is cooling attic air that leaks in as fast as the register pushes conditioned air out.

Replacement Cost & What’s Included

In Pasadena, a full Demilec attic air sealing redo runs $1,800-$3,400 for most single-family homes, with the final price driven by three things: attic square footage, accessibility (truss vs. conventional framing, existing insulation that must be moved), and whether we’re chasing a single failure zone or sealing the full envelope. That price includes removal and safe disposal of degraded foam, surface prep, new Demilec or equivalent foam application at all top plates, wire and pipe penetrations, can light boxes, and duct boots, plus a post-job blower-door test, a pressurization reading that shows, in one number, how much air your building envelope was losing before and after.

We do not quote by the square foot over the phone. Haven Standard Clause 1: flat price, written scope, written warranty before anyone lifts a tool. Every job gets a Documented Photo Record, and on applicable work, before-and-after blower-door numbers so you can verify the result yourself. The 365-Day Done Right Promise covers all completed sealing work.

DIY or Call Us?

Here’s what you can safely check yourself: look at the foam color and texture from the attic hatch with a flashlight, note any obvious gaps at visible top plates, and take photos of any data tags you find. What you should not do is attempt to cut out and replace Demilec foam yourself. Two-part spray foam requires respirator-rated PPE, controlled temperature and humidity for proper cure, and precise mix ratios that shift with ambient conditions. In Pasadena’s dry summer heat, DIY kits from hardware stores often skin over before achieving full density, leaving a hardened shell with uncured interior that off-gasses for months. We’ve pulled back homeowner-applied foam that read as “done” but leaked like a sieve on the blower-door test.

Seal the leaks first. Then insulate. The numbers will tell you why. Call (213) 816-5351 for a free estimate with a written price before any work starts.

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