Demilec Attic Air Sealing Nationwide | Walt’s Insulation

Demilec Attic Air Sealing: The Santa Monica Owner’s Guide

We stock, match, and install Demilec-compatible attic air sealing in Santa Monica, with most jobs running $1,200 to $2,800 installed depending on attic size and how much of the existing seal has failed. If you’re reading this, you’ve probably already found the telltale signs: a spike in your energy bill, a spare bedroom that won’t hold temperature, or dust showing up on boxes in the attic. You can call us at (424) 396-5828 and have a technician look at it same-day. Here’s what you need to know before you spend a dollar.

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Most Santa Monica homeowners discover their Demilec air sealing has failed because they feel it first. A room that gets hot by 2pm. A cold draft near the ceiling in winter. Then they climb up, look around, and see the sealant pulling away from framing members or crumbling in place. Demilec’s open-cell and closed-cell spray foam products are genuinely good materials. But no air seal survives forever in an attic, especially within a few miles of the Pacific where overnight condensation works on everything.

Which Demilec Models This Applies To

Demilec doesn’t make a single “air sealing” product. Their attic air sealing typically uses one of two spray foam lines: Sealection 500 (open-cell, half-pound density) or Heatlok HFO Pro (closed-cell, two-pound density). The open-cell Sealection is what we see most often in Santa Monica attics because it’s flexible enough to move with older framing and it allows moisture to pass through rather than trapping it. The closed-cell Heatlok is more common on larger custom homes and anywhere a homeowner wanted structural rigidity along with the air seal.

Here’s the compatibility gotcha most people miss: Demilec’s foam expands and cures differently depending on substrate temperature and humidity. If the original install happened on a damp morning, or if the attic ventilation was poor at the time, the foam may have cured with micro-voids that don’t show up for 2-4 years. When that happens, you can’t just spot-patch it. The failed sections need to be cut back to clean substrate and re-sprayed with the same product line or a compatible equivalent. We walk every attic and verify which product you have before we quote anything. OEM Demilec material is what we use when it’s available, but for older Sealection jobs we sometimes recommend an equivalent open-cell from another manufacturer that performs identically at a better price. We’ll tell you which way we’d go and why, before you commit.

Signs Your Demilec Attic Air Sealing Is Failing

• Rooms below the attic swing 10+ degrees between day and night. Your air seal is gone in spots, so the conditioned air leaves and the attic air comes in. The HVAC system works harder to compensate, which is why the energy bill follows the same curve.
• You see foam pulling away from rafters, top plates, or around penetrations. Demilec foam can shrink slightly over years of marine air cycling. When it separates from framing, you get a continuous gap that lets air move freely. This is the most common failure we find in Santa Monica homes built before 2010.
• Dust or insulation particles are showing up on stored boxes. Air moving through the attic carries fine particulates. If the seal around can lights, plumbing stacks, or the attic hatch has failed, that dust gets pushed down into living space through those gaps.
• You hear wind noise near the attic access on breezy afternoons. Santa Monica gets steady onshore wind most afternoons. A failing seal turns that breeze into an audible draft through the hatch gap or around vent stacks.
• Your pest problem came back after exclusion work. Rodents and insects find their way in through open air paths. If the seal has gaps, the rodents will keep finding them. We see this often in older bungalows near Montana Avenue where the original seal predates a remodel.

Replacement Cost & What’s Included

In Santa Monica, removing failed Demilec air sealing and re-spraying a typical 1,200 to 1,800 square foot attic runs $1,200 to $2,800 installed. That includes cutting back failed sections, cleaning the substrate, re-spraying with Demilec or an equivalent open-cell foam, and a full inspection of all penetrations (can lights, plumbing vents, exhaust fans, hatch). Larger attics with extensive failure, or jobs requiring closed-cell Heatlok, can push to $3,500 or more.

Every job includes our Done Right Promise: lifetime workmanship. If the seal fails because we didn’t do the job right, we come back and fix it. No runaround. Walt Brenner has been running crews in Santa Monica since the early 2000s, and he will tell you the same thing the first time he sees your attic: the material matters less than the person behind the gun. That’s why we don’t subcontract.

DIY or Call Us?

You can safely do two things yourself: visually inspect the seal for obvious gaps or crumbling, and take photos so you have a record. That’s it. Spray foam air sealing is not a caulk-and-walk project. The chemistry is temperature-sensitive, the expansion rate varies by product line, and a bad application can trap moisture against framing and create a mold problem you won’t see until it’s serious. We’ve been called in to fix DIY seal jobs that took a homeowner a full weekend and ended up costing more to undo than the original quote would have been. If you’ve got failing Demilec in your attic, call us at (424) 396-5828. We’ll look at it, tell you what’s actually wrong, and give you a number. No pressure, no games.

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