Demilec Attic Air Sealing Nationwide

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

We stock and install Demilec-compatible attic air sealing materials throughout San Diego, with most jobs running $1,400 to $3,800 depending on attic size and how much of the existing sealant has failed. Same-day and next-day appointments are available in most San Diego neighborhoods, and the technician arrives with the sealing material, spray rig, and safety gear already on the truck. Most homeowners discover the problem because their upstairs rooms won’t hold temperature and their energy bill climbs in August.

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Here’s the pattern we see across San Diego: a house built between 1995 and 2015 had Demilec spray foam or sealant applied at construction, it worked well for years, and then small gaps started opening around plumbing penetrations, recessed lights, and attic hatches. The foam didn’t fail everywhere at once. It degrades in specific spots, usually where heat, moisture, or settling stress hit first. Coastal homes in Ocean Beach and Point Loma see salt-air surface cracking while inland homes in Rancho Bernardo and Scripps Ranch deal with thermal expansion gaps. Both failures cause the same symptom: conditioned air escaping through the attic boundary.

Which Demilec Models This Applies To

Demilec makes two product lines that matter for attic air sealing: their open-cell spray foam (Heatlok Soya and Sealection 500) and their closed-cell formulations (Heatlok HFO Pro and Heatlok XT). The air sealing component isn’t a single “part” you can pick up at a hardware store. It’s the foam itself, applied as a continuous seal across the attic floor, top plates, penetrations, and the attic hatch perimeter. When we come out for a repair, we’re typically matching the existing foam chemistry and density so the new seal bonds correctly with the old material.

The compatibility gotcha most people run into: open-cell and closed-cell foams are not interchangeable in a repair. If your original application was open-cell Sealection 500 and someone patches it with closed-cell foam, you get a brittle interface that cracks within a season. We identify what’s there before quoting. Our techs check the foam’s color, density feel, and any remaining product labels on the rim joists or attic supports. We also confirm whether the original installer used a Demilec thermal barrier coating over the foam, because San Diego code requires that barrier on occupied attic boundaries, and any repair we do must restore it to code.

We stock Demilec product on the truck for most residential repairs. For less common formulations or older discontinued lines, we’ll order the correct material before the work date. We also carry Reflectix for radiant barrier sections that need replacement, since some San Diego attics pair Demilec foam with a foil radiant barrier on the roof deck. Aspen Attic Insulation San Diego is an independent service provider and not affiliated with Demilec, which matters only in that we have no incentive to sell you a full re-spray when a targeted repair will do.

Signs Your Demilec Attic Air Sealing Is Failing

• Upstairs rooms run 6 to 10 degrees warmer than downstairs in summer. The attic boundary is leaking, and hot attic air is pushing through gaps the foam used to seal. This is the most common first symptom in San Diego’s east county, where summer attic temps regularly hit 140 degrees.
• You can feel a draft near attic hatches, ceiling lights, or bathroom fans. A failing air seal leaves a pressure path. Run your hand around a recessed light can on a hot afternoon. If you feel warm air moving, the seal at that penetration has opened.
• Your energy bill jumped 15% or more without a rate change or new appliance. Attic air leakage directly drives cooling costs. SDG&E rate tiers punish that extra usage, so a failed seal costs more in San Diego than it would in a milder climate.
• Dust or insulation fibers accumulate near ceiling fans and light fixtures. Air movement through the ceiling plane carries fine attic dust down into the living space. New dust that reappears within days of cleaning points to an open air path.
• The attic smells or feels humid, or you find moisture stains on the underside of the roof decking. A failed air seal lets humid conditioned air into the attic, where it condenses against cooler surfaces. Over time, that means mold risk, especially in San Diego’s coastal zones where marine layer humidity persists.

Replacement Cost & What’s Included

For a typical San Diego single-family home, expect these ranges:

• Targeted air seal repair (3 to 8 penetration points): $850 to $1,600
• Full attic floor air seal plus hatch sealing (1,200 to 1,800 sq ft attic): $1,900 to $3,200
• Complete Demilec re-application on compromised open-cell foam (larger attics with widespread cracking): $3,400 to $5,800

Every quote is written and fixed before work starts. No allowances, no “we’ll see what we find” pricing. The tech does a full attic walkthrough first, points out exactly which seals have failed, and writes the price for labor and material in the same sentence. That price includes cleanup, disposal of any removed material, and a follow-up infrared check to confirm the seal is continuous. The work carries our 365-Day Done Right Promise in writing. If a repaired seal fails within a year, we return and fix it free, no second invoice.

DIY or Call Us?

You can safely identify the problem yourself. Walk the attic with a flashlight and look for visible gaps, cracked foam, or daylight showing through at penetrations. Mark those spots with masking tape. Take photos. That helps you make an informed decision and gives us a head start on scoping the work.

The repairs themselves are where DIY goes wrong. Demilec foam requires protective equipment, precise mixing and temperature control, and knowledge of how spray foam expands and cures. Apply the wrong density or get the substrate damp and you’ll have a bigger problem than you started with. If the existing material is closed-cell and you patch with open-cell, the thermal boundary won’t be continuous, and you’ve spent money on a fix that won’t fix anything. If you’ve already identified the leaks and want an honest recommendation on whether repair or re-seal makes sense, call us at (858) 282-0169. One of our techs will walk the attic, show you what they found, and quote you a price before any work is scheduled.

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