Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The San Diego Owner’s Guide

If you’ve got Demilec spray foam in your San Diego attic and the air seal is failing, we stock the compatible sealing materials and can typically get a crew out same-day or next-day. Most Demilec attic air sealing touch-ups and re-seals in San Diego run between $450 and $1,400 depending on how much of the existing foam needs to be cut back and re-applied, and you’ll get a written price before we touch anything. The way homeowners usually find us: an upstairs room that’s suddenly five degrees warmer in August, a musty smell near the attic hatch, or an energy bill that crept up with no obvious explanation. That’s the air seal telling you it’s done its job and needs attention.

Call (619) 344-8538

Which Demilec Models This Applies To

Demilec makes two main spray foam lines that show up in San Diego attics: the Heatlok HFO series (closed-cell, used for the air barrier itself) and the Sealection 500 series (open-cell, typically installed against the roofline). Both rely on the foam forming a continuous air seal at every penetration: can lights, ceiling joists, plumbing vents, electrical chases, and the attic hatch frame. If you’re trying to identify which product you have, look for the Demilec label on the inside of the attic hatch or on a joist near the access point. Heatlok HFO is rigid, dense, and has a slightly glossy surface; Sealection 500 is softer, lighter, and you can press a thumbnail into it. The compatibility gotcha we see often: Heatlok HFO and Sealection 500 use different blowing agents and cure chemistry, so touch-up foam must match the original. Generic can foam from a hardware store will stick, but it won’t bond chemically the way a Demilec-matched product does, and in San Diego’s heat it can pull away within a season or two. We carry both Demilec product families on our trucks, plus quality aftermarket equivalents that meet the same spec for homeowners who want a lower material cost.

Signs Your Demilec Attic Air Sealing Is Failing

• Upstairs rooms that won’t hold temperature. When the air seal at the ceiling plane fails, conditioned air leaks into the attic and pulls hot outside air in through every gap. If your upstairs thermostat reads 78 but the room feels like 84, that’s the classic symptom.
• A sudden spike in dust, especially in bedrooms. Attic insulation particles and fine dust get drawn down through ceiling penetrations when the air seal breaks. If you’re dusting twice as often as last year, check the attic.
• Musty or stale smell near the attic hatch. Failed air sealing lets humid attic air exchange with living space. In San Diego’s coastal zones, that moisture lands in the foam and can grow mold on the surface.
• Visible shrinkage or cracking in the foam. Demilec foam that’s been exposed to San Diego’s heat cycling for 10+ years can shrink at the edges or crack along joist lines. Shrinkage gaps of even a quarter inch break the air seal.
• Higher energy bills with no change in usage. A compromised air seal forces your HVAC to run longer to hold the same indoor temperature. If your bill went up 15-20% without a rate change, the attic is the first place we look.

Replacement Cost & What’s Included

For a typical San Diego single-story home of 1,400 to 2,200 square feet, re-sealing the attic air barrier with Demilec-matched foam runs $450 to $900 when the failure is localized (hatch frame, a handful of can light penetrations, one or two joist seams). A full attic re-seal where the original foam has shrunk or cracked across most of the ceiling plane runs $900 to $1,400. The range depends on attic accessibility, how much old foam needs to be cut out and removed before re-application, and whether we’re working around stored belongings. Every quote includes the removal, the prep, the Demilec-compatible foam, labor, and our written 365-day guarantee. That guarantee means if the re-seal fails within a year, we come back and fix it at no charge. No exceptions, no fine print.

DIY or Call Us?

Spray foam air sealing involves handling two-part chemical foam that expands on contact and cures rapidly. If applied incorrectly, it can over-expand into wiring, jam attic hatches shut, or create a worse seal than you started with. Working in a San Diego attic in August also means surface temperatures above 120 degrees, which shortens the foam’s working time and makes a clean application genuinely difficult. What you can safely do yourself: inspect the attic with a good flashlight, note where the foam has cracked or pulled away, and measure the gaps so you have real information when you call. What we’d rather you not do: climb up there with hardware-store can foam and hope for the best. That foam won’t match Demilec’s chemistry, and the fix tends to fail within a season. Call us at (619) 344-8538 and we’ll give you a written price before any work starts.

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