Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Pasadena Owner’s Guide

We stock and install Demilec-compatible attic air sealing materials throughout Pasadena, with most jobs running $1,200 – $2,800 depending on attic square footage and how much of the existing seal has broken down. Same-day or next-day service is available for most homes, and every job includes a written price before work begins. The way most Pasadena homeowners discover their Demilec air sealing has failed isn’t dramatic; it’s a slow drift upward in the summer electric bill, a bedroom that won’t hold temperature, or dust showing up on stored boxes that were clean six months ago.

Call (626) 628-2368

Demilec’s open-cell and closed-cell spray foam products are good materials. What fails around them in the attic is usually the sealing system; the foam-to-wood transitions, the can-light covers, the top plates, and the hatch gaskets. That’s what this page covers.

Which Demilec Models This Applies To

Demilec manufactures spray polyurethane foam under several product lines, and the attic air sealing around them differs by foam type. The two you’re most likely to have in a Pasadena attic are Sealection 500 (open-cell, half-pound foam) and Heatlok HFO Pro (closed-cell, two-pound foam). Each requires different sealing approaches at the transitions, and the compatibility gets specific. Open-cell foam is vapor-permeable, which means the air seal around it has to account for moisture movement through the foam itself. Closed-cell is a vapor barrier on its own, so the perimeter sealing works differently.

Here’s a compatibility detail most homeowners never hear: if your attic has mixed foam, where a previous contractor used open-cell on the roof deck and closed-cell on the gable walls, the transition seam between the two is a common failure point. The foams expand and contract at different rates during a Pasadena summer, when attic temperatures swing from the 50s at night to over 120 degrees by mid-afternoon. Over five or six years, that seam opens up. We look for it on every Demilec air sealing job, because it’s the first thing that fails.

As for the parts themselves: Demilec doesn’t sell a branded “air sealing kit” for retrofit work. What’s needed are the compatible sealants, gaskets, and foam products that match the existing Demilec installation. We stock OEM-equivalent materials from Demilec’s approved supplier network, and we also carry Reflectix products for radiant barrier and duct wrap applications where the job calls for it. If you’re unsure what’s in your attic, the foam color and texture usually tell us: open-cell is softer and lighter, closed-cell is dense and rigid.

Signs Your Demilec Attic Air Sealing Is Failing

• Temperature difference between rooms. The bedroom over the garage runs five or six degrees warmer than the rest of the house. This usually means the air seal above that room has opened up, and conditioned air is escaping into the attic while hot attic air pushes down through the ceiling.
• Dust accumulating on stored items faster than it used to. Air sealing failure lets fine particulate from the attic settle into the living space. If you’re wiping a gray film off boxes in the attic every few months, the seal is compromised.
• A musty smell that comes and goes, especially after rain. Pasadena gets most of its rain between December and March, and a broken air seal lets humid outside air into the attic cavity where it condenses against the foam, which can develop odor over time.
• Utility bills creeping up without a change in usage. We hear this constantly. The bill from Pasadena Water and Power climbs $30 – $50 a month year over year, and nothing else in the house changed. Air sealing failure is almost always part of it.
• Visible gaps or cracking at foam-to-wood junctions. If you can see daylight or feel air moving around the edges of the foam where it meets rafters or top plates, the seal is gone in that spot. Whether it’s the original installation aging out or a material incompatibility, it needs attention.

Replacement Cost & What’s Included

For Pasadena homes, Demilec attic air sealing replacement typically runs $1,200 – $2,800 installed. The range is driven by three things: the attic’s square footage, the condition of the existing foam (we may need to remove and reapply sections that have delaminated from the wood), and accessibility. A low-slope roof with tight clearances takes longer than an open walkable attic, and that labor cost is real.

Every quote we give includes parts and labor in one written number. No separate line items that change later. The work is covered by our 365-Day Done Right Promise: if the sealing fails within a year, we come back and make it right at no charge. That’s in writing, and it’s non-negotiable. Bryce Holloway built Alden around this guarantee because he’s spent too many hours tearing out other contractors’ shoddy work across the San Gabriel Valley to let his own crew follow that example.

DIY or Call Us?

Here’s the straight answer. You can safely check the visible seams, look for daylight around the hatch, and note where the foam has pulled away from the rafters. That’s useful information to have before you call anyone. But actually applying spray foam air sealant in an attic is not a weekend project. The foam components are chemical products that require proper ventilation, protective equipment, and a specific application temperature range. Get the mix wrong in a 120-degree Pasadena attic and you’ve got a mess that costs more to fix than the original job.

There’s also the reality of what you can’t see: most air sealing failures happen at the top plates behind existing insulation, where you’d have to move material aside to even find the gap. If you’ve already got the symptoms, give us a call at (626) 628-2368. We’ll tell you over the phone whether it sounds like a sealing issue or something else, and we’ll give you a written price before any work starts.

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