Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Los Angeles Owner’s Guide

We stock and install Demilec-compatible attic air sealing components across Los Angeles, with most residential jobs running between $1,800 and $3,400 installed depending on attic square footage and penetration count. Same-day service is available when we have your configuration in the van, which we do for the common Demilec APX and Heatlok HFO series used in Southern California retrofits since 2014. Most Los Angeles homeowners discover their Demilec air sealing has failed when their summer cooling bills spike despite unchanged thermostat settings, or when a home energy audit reveals attic bypasses that the original spray foam never fully sealed.

Call (628) 226-1097

Which Demilec Models This Applies To

Demilec’s attic air sealing systems fall into two main families we encounter in Los Angeles homes: the APX series (open-cell, 0.5 lb/ft³ density, typically sprayed at 3-5 inches for attic floors) and the Heatlok HFO series (closed-cell, 2.0 lb/ft³ density, used for rim joists and critical air barriers in conditioned attics). The part you’re looking for depends on which assembly failed: the foam itself, the substrate adhesive, or the flash-and-batt hybrid components Demilec specifies for Title 24 compliance.

To identify your system, check the spray-foam technician’s left-behind documentation - every Demilec-certified applicator is required to post a job card with the product lot number and applied thickness. No card? Measure the cured foam density with a simple kitchen scale and ruler: open-cell APX weighs roughly half a pound per cubic foot and compresses easily between thumb and forefinger; closed-cell Heatlok feels rigid and weighs four times as much. We carry replacement foam kits, compatible substrate primers, and retrofit air-sealing assemblies for both series on our Los Angeles service van.

Topside Attic Insulation Los Angeles is an independent service provider, not affiliated with Demilec. We source Demilec-compatible materials through our supply chain alongside Owens Corning, Johns Manville, Knauf, Rockwool, CertainTeed, Icynene, and GreenFiber - no proprietary lock-in means we match the right product to your existing assembly rather than forcing a full tearout.

Signs Your Demilec Attic Air Sealing Is Failing

• Hot second-floor rooms in July and August despite running the AC continuously. Demilec open-cell foam can shrink 2-3% over its first two years; in Los Angeles’s dry heat, that shrinkage pulls away from top plates and chimney chases, reopening bypasses that conditioned air escapes through. The thermostat keeps calling, the unit keeps running, and the upstairs never catches up.
• Dust streaks on ceiling drywall near recessed can lights or HVAC registers. These dark lines are filtration soiling - attic air being pulled through gaps the Demilec foam was supposed to seal, carrying fiberglass particles and whatever else is floating above your ceiling. We see this most in 1960s ranch homes in the Leimert Park corridor where original soffit chases were never properly blocked before foam application.
• Ice damming or moisture staining at the roof edge in winter rains. Even in mild Los Angeles winters, a compromised air barrier lets warm, humid interior air reach cold roof sheathing. The moisture condenses, saturates insulation, and shows up as staining or, in rare freeze events, ice at the eaves. Demilec closed-cell is more resistant to this, but only if the specified thickness was actually achieved - we’ve measured 1.2 inches where 2 inches was specified.
• Blower-door test shows minimal improvement after “insulation upgrade.” A contractor blew new cellulose or fiberglass over your Demilec foam without sealing the bypasses first. The R-value went up; the air leakage didn’t change. We run into this in Eagle Rock and Highland Park regularly - the homeowner paid for insulation and got almost no envelope tightening because the holes were never sealed.
• Spray foam visible from the attic side is cracked, yellowed, or separating from framing members. UV degradation from attic gable vents or degraded adhesive from improper substrate prep - common in rush jobs during the 2016-2018 Title 24 compliance boom - breaks the air seal. The foam is still there, but it’s no longer doing the one job it was installed for.

Before

After

Replacement Cost & What’s Included

What drives the range: attic square footage, number of penetrations to seal, accessibility (truss vs. stick-framed, existing insulation depth), and whether we need to remove degraded material first. Every job gets a Written Price Before Any Work Starts - Haven Standard Clause 1 - with line-item scope, product specification, and the 365-Day Done Right Promise in writing before anyone lifts a tool. We also publish before-and-after blower-door numbers on every applicable job so you can verify the air-sealing result in a single figure: CFM50 before, CFM50 after, and the percentage reduction.

DIY or Call Us?

Here’s what you can safely check yourself: read the job card left by your original installer for the Demilec product series and applied thickness; use a flashlight to inspect visible foam from the attic access for cracks, shrinkage gaps, or separation from framing; and note any hot rooms, dust streaks, or moisture stains to report accurately.

Here’s where DIY goes wrong: two-component spray foam requires respirators with organic vapor cartridges, full skin coverage, and precise substrate temperature control - Los Angeles attics hit 140°F in August, far above Demilec’s application spec. Improper mixing ratios or moisture contamination produces foam that looks cured but never achieves specified density, meaning you’ll pay twice when it fails again in two years. And without a blower-door test, you cannot verify that the air seal actually worked. We carry calibrated blower-door equipment on every Los Angeles van and run it before and after - no exceptions. For a written price and same-day availability assessment, call (628) 226-1097.

FAQs