Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Austin Owner’s Guide

We stock and install Demilec-compatible attic air sealing materials throughout Austin, with most jobs running between $450 and $1,100 depending on attic size and how much sealing area needs attention. Same-day service is available for most homes inside Austin and the surrounding metro. You’ll usually know something’s wrong when your upstairs starts feeling muggy in July, your AC can’t hold a setpoint, or you spot dust trails leaking through ceiling fixtures.

Call (361) 321-0817

Demilec air sealing products, particularly the Sealection series, work as a two-in-one insulation and air barrier. When that barrier breaks down or was never installed correctly in the first place, Austin’s humidity presses in through every gap. The result is an attic that works against your HVAC rather than with it.

Which Demilec Models This Applies To

The Demilec air sealing conversation in Austin almost always involves two product families: Sealection 500 and Sealection Agribalance. Both are open-cell, semi-rigid spray foam formulations designed for attic application, though they behave differently in practice. Sealection 500 is the more common residential choice here, while Agribalance uses a soy-based formula some homeowners prefer for its lower off-gassing profile.

OEM identification is straightforward: look for the Demilec label on the foam surface or on the original job invoice. If neither exists, we measure the foam’s density and cell structure on site. A compatibility gotcha we run into regularly in Austin: Sealection 500 and Agribalance have different expansion characteristics, and layering one over the other without addressing the underlying adhesion issue leads to premature delamination. We carry OEM-compatible materials for both lines on our trucks, along with quality aftermarket options that match Demilec’s performance specs when a homeowner prefers a lower-cost alternative.

Signs Your Demilec Attic Air Sealing Is Failing

• Upstairs rooms run 5-8 degrees warmer than downstairs. The air barrier has developed gaps or the foam has pulled away from the sheathing, letting attic heat push into living space. This is the most common Demilec failure we see in Austin summers.
• Visible shrinkage or cracking at foam edges. Open-cell foam expands and contracts with temperature swings, and Austin’s 100-degree summer days followed by cooler nights stress the material at the foam-to-wood junction until it separates.
• Dust trails around ceiling fixtures and registers. Air is moving through the attic floor where the foam should have stopped it. Look for gray streaks on the ceiling around lights, fans, and HVAC vents.
• A sudden spike in your electric bill during mild months. When the air seal fails, your HVAC works harder in October and April, not just August. Austin homeowners often notice this in the fall before the heat hits again.
• Musty smell in the attic after rain. Failed air sealing lets humid outdoor air into the attic cavity, where it condenses on cooler surfaces. That moisture feeds mold and degrades the foam further.

Replacement Cost & What’s Included

Here’s what Demilec attic air sealing replacement looks like in Austin, based on the jobs we’ve completed across the metro:

• Small attic (up to 800 sq ft, partial repair): $450 – $700
• Medium attic (800 – 1,400 sq ft, section replacement): $700 – $900
• Large attic (1,400+ sq ft, full re-seal): $900 – $1,100
• Add-on: insulation removal before re-sealing: $300 – $600 depending on depth and material type

Every quote includes the foam material, surface prep, application, and cleanup. We give you a written price before any work starts, and the number on that sheet is the number you pay. The 365-Day Done Right Promise covers the workmanship in writing: if the seal fails within a year, we come back and fix it at no charge. If it fails after that, you still get a free second visit to diagnose what went wrong.

DIY or Call Us?

Spray foam air sealing is not a weekend DIY project. The chemicals involved in two-part foam applications require proper mixing ratios, the right equipment, and real ventilation discipline. A bad mix looks fine for a few months and then fails catastrophically under Austin’s heat load. That said, you can absolutely inspect your own attic: look for visible shrinkage at foam edges, check for daylight through soffit cracks, and note any dust-trail patterns on the ceiling below. If you see these signs, call us at (361) 321-0817. We’ll tell you honestly whether it’s a patch job or a full re-seal, and we’ll quote it before we start. Tell me your square footage and I’ll give you a real number – no runaround.

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