Demilec Attic Insulation Nationwide | Walt’s Insulation

Demilec Attic Insulation: The Sunnyvale Owner’s Guide

We stock and install Demilec-compatible spray foam and blown-in attic insulation throughout Sunnyvale, with most jobs running $1,800 to $4,600 depending on square footage and whether you’re topping off existing insulation or starting fresh after a removal. Same-day and next-day appointments are available, and we carry Demilec’s open-cell and closed-cell lines on our trucks when we roll up to your house. Most Sunnyvale homeowners discover their Demilec insulation has failed the hard way: a bedroom that won’t hold temperature in August, a spike in the electric bill, or damp spots on the ceiling where condensation has found a gap. By the time you can feel the problem from your living room, the attic has usually been under-insulated or compromised for months.

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Which Demilec Models This Applies To

Demilec makes two main spray foam lines we work with in Sunnyvale attics: Heatlok HFO (closed-cell, roughly R-7 per inch) and Sealection 500 (open-cell, roughly R-4 per inch). Both come in two-part kits, and both have the same Achilles’ heel: if the A-side and B-side don’t mix at the right temperature and ratio, the foam never cures properly and you get a crumbly, shrunken mess instead of a solid air barrier. The quickest way to identify what’s in your attic is the color and texture: Heatlok cures to a dense, yellowish foam you can knock on like a door, while Sealection cures white and softer, almost like a sponge. For OEM versus aftermarket: Demilec foam is sold through licensed distributors, and there is no meaningful “aftermarket” version of the chemistry itself. What matters is who’s running the gun. We’re an independent installer, not affiliated with Demilec, so our recommendation is based on what works in Bay Area attics, not a brand loyalty quota.

Signs Your Demilec Attic Insulation Is Failing

• Cold spots or hot spots in rooms directly under the attic. This usually means the foam has pulled away from the roofline or gable ends, leaving a channel for outside air to pour through. In Sunnyvale’s older ranch homes near Murphy Avenue, we see this most often where original framing has settled and split the foam at the seams.
• A musty or “chemical” smell that gets stronger on hot days. Open-cell foam that didn’t cure fully can off-gas and hold moisture. If the smell showed up after install and never went away, the chemistry was wrong from day one.
• Attic temperatures that swing wildly between day and night. Demilec’s closed-cell foam is designed to even out the thermal lag. When it’s working, the attic should track close to the home’s interior. A 30-degree swing in 24 hours means the air seal has failed somewhere.
• Visible shrinking, cracking, or flaking foam at seams and joints. Closed-cell foam can shrink slightly as it ages, but big gaps around rafters or vents are a red flag. That’s air moving where it shouldn’t be.
• Higher cooling bills with no other explanation. Sunnyvale’s summer heat doesn’t mess around, and your AC is the canary in the coal mine. If the system is running longer to hold the same temperature, the attic insulation is the first place we look.

Replacement Cost & What’s Included

For a typical 1,200 to 1,800 square foot Sunnyvale attic, expect to pay somewhere in this range:

• Open-cell (Sealection-type) full attic: $1,800 to $3,200
• Closed-cell (Heatlok-type) full attic: $3,200 to $4,600
• Spot repair of failed sections: $600 to $1,500 depending on access and how much old foam needs cutting out first
• Blown-in Demilec-compatible fiberglass or cellulose to top off existing coverage: $900 to $1,800

Every quote includes removal of failed material if needed, new foam or blown-in install, cleanup, and disposal. We back the workmanship with the Done Right Promise: if it’s not done right, we make it right, no runaround and no invoice. We also offer a free second opinion on any written estimate, so if another company has already given you a price, bring it to us and we’ll tell you straight whether it’s fair. And don’t forget the $40 off any repair over $200, plus our permanent 10% discount for seniors and veterans.

DIY or Call Us?

Here’s the honest split. You can safely check your attic for visible gaps, crumbling foam, or damp spots along the roofline. That’s a flashlight-and-eyeballs job, and it’s worth doing once a year. What you shouldn’t do is attempt to re-spray Demilec foam yourself. The two-part chemical reaction happens at high temperature, the uncured material is a respiratory and skin hazard, and a DIY kit from a hardware store will not match Demilec’s chemistry for coverage or R-value. We’ve fixed enough botched DIY spray jobs in Sunnyvale to know the pattern: the homeowner saves a few hundred dollars and spends thousands on removal and redo. If you see failed foam, call (669) 215-4805 and we’ll come assess it. Good insulation should be invisible, you only notice it when it’s missing.

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