Demilec Attic Insulation Nationwide

Demilec Attic Insulation: The San Francisco Owner’s Guide

Demilec attic insulation replacement in San Francisco typically runs $2,200 to $6,800 installed, depending on square footage, current R-value, and whether we’re pulling out old material first. Alden Insulation San Francisco stocks Demilec Heatlok HFO and Sealection 500 on the truck, and we can usually get a crew out same week, often same day. Most San Francisco homeowners discover their Demilec insulation has failed the same way: a bedroom that won’t hold heat in July fog, an energy bill that climbs without explanation, or a musty smell coming from the attic hatch after a wet winter.

Call (559) 245-9792

We’re an independent service provider, not affiliated with Demilec. That matters because we evaluate what your attic actually needs rather than pushing a product line. Bryce Holloway has spent years working older San Francisco homes, and the pattern with Demilec failures is consistent: the foam delaminates from the roof deck, or moisture gets trapped where it shouldn’t, and the R-value quietly drops until you notice something’s wrong.

Which Demilec Models This Applies To

Demilec makes two primary spray foam lines we see in San Francisco attics: Heatlok HFO, a closed-cell foam, and Sealection 500, an open-cell product. The closed-cell Heatlok HFO runs about R-7 per inch and acts as its own vapor barrier. Sealection 500 runs closer to R-3.8 per inch and breathes, which matters in coastal San Francisco where attics fight moisture year-round.

Here’s the compatibility gotcha most homeowners miss: you cannot patch open-cell over closed-cell, or vice versa, without creating a moisture trap at the seam. If your attic has Heatlok HFO on the roof deck, the repair has to match. If it’s Sealection 500, switching to a closed-cell product mid-attic can lock condensation inside the older foam and cause rot in the sheathing. We verify the existing material before quoting anything.

On the OEM versus aftermarket question: Demilec doesn’t sell “replacement parts” for cured foam. The material itself is the product. What fails is the installation or the substrate beneath it. That means the real decision isn’t OEM versus aftermarket, it’s whether we remove and re-spray, or overlay with a compatible brand like Owens Corning or Knauf fiberglass where spray foam no longer makes sense for the structure.

Signs Your Demilec Attic Insulation Is Failing

• Uneven room temperatures between floors. Closed-cell foam that has delaminated from the roof deck leaves gaps where conditioned air escapes. The upstairs runs five to eight degrees warmer than the living room, and no amount of thermostat adjustment fixes it.
• A musty or chemical smell near the attic hatch. Open-cell foam that has absorbed moisture from San Francisco fog will off-gas a stale, damp odor. It’s not dangerous at typical levels, but it signals trapped water somewhere in the assembly.
• Visible gaps between foam and framing. If you peek into the attic and can see daylight or gaps where foam has pulled away from rafters, the air seal is broken. Even a quarter-inch gap cuts the effective R-value significantly.
• Energy bills creeping up without a rate change. PG&E rates fluctuate, but if your usage climbed while your habits didn’t, the attic is the first place we look. Degraded Demilec foam can lose 20 to 30 percent of its effective R-value before it’s visible to the eye.
• Condensation on roof nails or sheathing. In San Francisco’s damp climate, failed open-cell foam lets warm interior air hit cold roof decking. The resulting condensation rusts nails and stains wood, and left alone, it rots the decking.

Replacement Cost & What’s Included

For San Francisco attics, here’s the straight pricing picture:

• Full removal and re-spray of Heatlok HFO: $3,800 – $6,800 for a typical 800 – 1,200 square foot attic
• Full removal and re-spray of Sealection 500: $2,200 – $4,200 for the same footprint
• Partial repair of delaminated sections: $850 – $2,400 depending on square footage and access
• Air sealing before new foam: $400 – $1,100, and we won’t spray without it, because foam over leaky penetrations just hides the leak

Every Alden Insulation San Francisco quote is written before any work starts. The number you approve is the number on the invoice. We don’t revise at the door. And every job carries the 365-Day Done Right Promise: if the work fails within a year, we return and make it right at no charge, including a free second visit if the repair doesn’t hold. That’s The Garrison Standard, and it applies to every attic we touch in San Francisco.

Good insulation doesn’t announce itself. You just stop noticing the cold.

DIY or Call Us?

You can safely inspect the visible condition of your Demilec foam: look for gaps, discoloration, crumbling edges, or damp-looking spots near the eaves. Take photos, note the areas, and that’s where the DIY portion should end.

Spray foam removal and reapplication is not a weekend project. Cutting out cured closed-cell foam requires a respirator, containment, and careful handling; spraying new foam requires the right equipment, the right temperature and humidity conditions, and the right eye for how the material behaves on San Francisco’s older framing. Done wrong, you get the exact problem you’re trying to fix: trapped moisture, wasted money, and an attic that still doesn’t perform. If you’ve got visible Delamination, give us a call at (559) 245-9792. Bryce will give you a straight assessment of what’s needed and what isn’t.

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