Demilec Attic Air Sealing: The Los Angeles Owner’s Guide
We stock and install Demilec-compatible attic air sealing material in Los Angeles, and a full attic air sealing job on a typical 1,500 to 2,200 square foot home runs $1,800 to $3,400 installed, depending on attic size, access difficulty, and how much existing sealing has degraded. Most Los Angeles homeowners call us after noticing one of two things: a hot second floor despite a running AC, or visible gaps where the ceiling meets interior walls showing daylight from below. The fix is almost always faster than people expect, and we can usually schedule the job within the same week.
What trips up most LA homeowners is assuming the Demilec foam is the problem when, in fact, the failure is almost always in the sealing layer around it: the can foam, caulk, or weatherstripping that was never installed correctly around plumbing penetrations, recessed lights, and the attic hatch itself. The Demilec product rarely fails on its own. The perimeter work around it does.
Which Demilec Models This Applies To
Demilec makes open-cell and closed-cell spray foam products under the Heatlok and Sealection names, and the attic air sealing conversation in Los Angeles almost always involves one of these three: Heatlok HFO Pro, Sealection 500, or Sealection Agribalance. They are not interchangeable. Heatlok HFO Pro is a closed-cell foam with an R-value around R-7 per inch, typically used where you need structural rigidity and moisture control along the roofline. Sealection 500 is open-cell, around R-3.8 per inch, and acts more as an air barrier than an insulator, which is exactly what you want when the goal is stopping conditioned air from leaking out of the living space below.
Here is the compatibility gotcha that costs Los Angeles homeowners real money: if someone sealed your attic with Sealection 500 years ago, you cannot spot-fill failing areas with Heatlok and expect a good result. The two products expand differently and cure into different densities. The right fix is removing the failed section, preparing the surface, and reapplying the same family of product. We match the foam chemistry to what is already in your attic. If you cannot find the product label, it is usually stamped on the foam itself near the attic access point, or written on the permit paperwork from the original install. And yes, we have pulled up to LA homes where nobody ever pulled a permit. That is its own problem, and one we can help sort out.
Signs Your Demilec Attic Air Sealing Is Failing
- A hot second story in summer, even with the AC running. Air-sealing failures let cool air escape into the attic while hot attic air gets drawn into the living space. We see this constantly in older Los Angeles homes with original ceiling framing.
- Visible dust or grime staining around ceiling fixtures. When air leaks past recessed lights or ceiling fans, it carries fine dust that deposits in a telltale ring. That ring is the canary in the coal mine for a failed seal.
- A draft you can feel near the attic hatch. The hatch is the most common failure point in any Los Angeles home, because it gets opened and closed, the weatherstripping compresses, and nobody thinks to check it until the utility bill climbs.
- Mold or mildew scents coming from above. Warm, moist indoor air rising through an unsealed attic can condense on cooler roof decking in winter. In Los Angeles, this shows up most often in coastal homes with marine-layer dampness.
- Energy bills that trend upward year over year with no obvious cause. Air sealing degradation is gradual. We have seen homeowners blame their aging HVAC when the real culprit was a quarter-inch gap around a plumbing stack letting conditioned air pour into the attic.
Replacement Cost & What’s Included
For a typical Los Angeles single-family home, a full Demilec attic air sealing refresh lands between $1,800 and $3,400. If the roof deck is already covered in foam, you are looking at $800 to $1,400 for targeted top-up and sealing work around hatches, penetrations, and wall plates. Here is the breakdown:
- Inspection and leak mapping: included, no separate line item.
- Sealant removal and prep: $300 to $600 for typical attics, more if old foam needs cutting back.
- Demilec product application (open-cell or closed-cell): $0.40 to $0.75 per board foot installed, depending on depth and product type.
- Perimeter sealing (hatch, penetrations, top plates): $400 to $800 in most Los Angeles homes, including labor and material.
- Labor: baked into the per-board-foot and line item prices above. No surprise labor add-ons at the end.
Every job gets a written price before any work starts, and the labor and material are covered by our 365-Day Done Right Promise. If the seal fails within a year, we return and redo it at no charge. That is not a verbal assurance. It is written on every quote, every invoice, every time.
DIY or Call Us?
You can safely check your attic hatch seal, look for visible gaps around plumbing stacks, and run a hand along ceiling fixtures to feel for drafts. What you should not do is climb into a Los Angeles attic in July and start pulling back old foam. Attics here routinely hit 130 to 150 degrees in summer, and dislodging unknown sealant or working near recessed light housings can expose you to electrical hazards and rapid dehydration. Spray foam application also requires respirator protection and an understanding of how the product expands and cures in confined spaces. This is one of those times where the honest advice is this: the inspection is free, the repair is not a place to learn by trial, and our number is (864) 428-1615. You will know the price before we pull the hatch.
FAQs
Demilec foam itself is a 50-year product, but the sealing around it fails much sooner: five to ten years for typical can foam and weatherstripping in Los Angeles heat. The foam holds. The seams do not. Call (864) 428-1615 for an inspection if your home is past the ten-year mark since its last sealing work.
Yes, in most cases. If the foam is intact and the problem is gaps around penetrations, the hatch, or top plates, we can repair and re-seal those specific areas for a fraction of a full re-spray. We only recommend replacement when the original foam has pulled away from the decking or failed due to moisture.
Most Los Angeles attic air sealing jobs are done in one day. Larger homes with extensive failing areas may take two. We will tell you the exact timeline in the written quote before any work begins.
We keep Demilec Heatlok and Sealection material on hand for common Los Angeles attic sealing jobs, along with sealants, weatherstripping, and hatch gaskets. We also stock Reflectix products for radiant barrier work where the job calls for it. Specialized or unusual applications may take a few days to source, and we will tell you that honestly up front.
Call Aspen Attic Insulation for Demilec Sealing in Los Angeles
If your attic air sealing is failing, call (864) 428-1615 for a free inspection and a written price. We answer live, 24/7. You will get a technician’s name and photo sent to you before the visit, a background-checked and uniformed professional at your door, and a written guarantee covering the work for 365 days. We are an independent Los Angeles insulation contractor, not affiliated with Demilec, but we work with Demilec products because they hold up in this climate. Let us take a look and tell you exactly what your attic needs.
Written by Garrett Sloane, Owner, Aspen Attic Insulation at Aspen Attic Insulation, serving Los Angeles and nearby areas.