Demilec Attic Insulation Nationwide | Walt’s Insulation

Demilec Attic Insulation: The Hayward Owner’s Guide

If you’ve got Demilec spray foam or blown-in insulation in your Hayward attic and it’s failing, we stock compatible Demilec products and can typically get a crew out same-day or next-day. Installed replacement runs roughly $1.80 to $4.50 per square foot depending on whether we’re doing open-cell, closed-cell, or a blown-in Demilec fiberglass top-up, and that includes removal of the failed material, prep, installation, and cleanup. Most homeowners discover the problem the same way: a bedroom that won’t hold temperature, a spike in the PG&E bill, or visible settling when they climb up to grab the holiday decorations.

Call (510) 871-9022

We’re an independent insulation contractor, not affiliated with Demilec. That means we tell you straight what’s actually wrong, not what the warranty department wants to hear. And if the part that failed is something we can fix without a full re-insulation, we’ll say so.

Which Demilec Models This Applies To

Demilec makes two main lines that show up in Hayward attics: Heatlok HFO (closed-cell spray foam) and Sealection 500 (open-cell spray foam), plus the newer Heatlok XT and Sealection Agribalance lines. Closed-cell is the dense stuff, usually 2 to 3 inches thick, cream or pale yellow. Open-cell is softer, off-white to light gray, and typically 6 to 10 inches deep. If you’re not sure which you have, look at the foam texture: closed-cell feels hard like a foam cooler, open-cell feels like a firm sponge. The label is usually on the foam itself or on an invoice from the original install.

Here’s the compatibility gotcha most homeowners don’t know: you can’t spot-repair closed-cell Demilec foam with just any spray foam from the hardware store. Big-box cans are polyurethane, sure, but they’re a different density and cell structure. They won’t bond correctly to Heatlok, and you’ll end up with air gaps that defeat the whole purpose. For open-cell Sealection, a small can product can work for a patch under a square foot, but anything bigger needs a professional re-spray. We carry Demilec products on the truck along with quality equivalents from Icynene and CertainTeed, plus we stock Reflectix radiant barrier for the underside of the roof deck in hot Hayward summers.

Signs Your Demilec Attic Insulation Is Failing

• Rooms directly under the attic run 8-12 degrees hotter in summer. This usually means the foam has pulled away from the roof deck or settled, creating air channels that let heat pour through. We see this most often in older Hayward ranch homes where the original install was done thin.
• Drafts near recessed lights, attic hatches, or where walls meet ceiling. Foam shrinks as it ages, especially open-cell in dry California air. Gaps at penetrations open up first, and you feel it as a draft in rooms below, even with the windows closed.
• Higher PG&E bills in July and January with no change in usage. Attic insulation is the single biggest factor in Hayward home energy cost. When Demilec foam underperforms, the HVAC works harder and the bill shows it within one to two billing cycles.
• Visible settling, cracking, or dusty foam particles on attic surfaces. Open-cell Sealection in particular can degrade under high attic heat over 15 to 20 years. Hayward’s summer attic temps routinely hit 140°F, and that thermal cycling breaks down the foam’s cell structure slowly.
• Musty smell or condensation on the underside of the roof deck. Failed foam allows warm interior air to reach the cold roof deck, creating condensation that leads to mold. This is the one you don’t want to ignore.

Replacement Cost & What’s Included

In Hayward, you’re looking at three common scenarios. Full removal of failed Demilec open-cell and re-spray with new open-cell runs $1.80 to $2.75 per square foot installed. Full removal plus a switch to closed-cell Heatlok HFO runs $2.50 to $4.50 per square foot, and closed-cell is the better choice for roof decks in Hayward’s climate because it doubles as a vapor barrier. If the existing closed-cell foam is mostly intact and just needs a top-up coat or section repair, many jobs land between $800 and $2,400 total depending on square footage and access difficulty.

• Removal of failed foam: $0.60 to $1.20 per sq ft, included in the ranges above
• Open-cell re-spray (Sealection-type): $1.20 to $1.80 per sq ft installed
• Closed-cell re-spray (Heatlok HFO-type): $1.90 to $3.30 per sq ft installed
• Air sealing around penetrations: $150 to $400 depending on count, typically included in full re-insulation

Every quote includes a line-item breakdown, and all work is covered by our Done Right Promise: if it’s not done right, we make it right, no runaround. You also get $40 off any repair over $200, and seniors and veterans save 10% on every job, always. We answer the phone live because your attic doesn’t keep business hours.

DIY or Call Us?

You can safely check a few things yourself: look for visible gaps where foam meets the roof deck, check for settling or crumbling foam, and note where drafts are worst in the rooms below. Those observations help us give you an accurate phone quote. What you shouldn’t do is try to re-spray or patch Demilec foam yourself with store-bought cans. Improper mixing, poor substrate prep, or applying over moisture creates off-gassing problems, bad bonding, and wasted money. If you’re dealing with more than a tiny gap, call us at (510) 871-9022 and we’ll give you a straight answer on whether it’s a repair or replacement job.

FAQs