Demilec Attic Air Sealing Nationwide

Demilec Attic Air Sealing: The Houston Owner’s Guide

We install and replace Demilec attic air sealing in Houston, with most jobs running $1,900 to $3,800 depending on attic square footage, existing insulation condition, and how many penetrations need sealing. Our trucks carry Demilec-compatible sealant and we can usually schedule within 48 hours, not weeks. Most Houston homeowners discover their air sealing has failed when the upstairs room won’t hold temperature in August, or when the electric bill climbs 20% year over year without a rate change. You don’t hear air sealing fail. You pay for it.

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Which Demilec Models This Applies To

The Demilec air sealing conversation in Houston usually starts with one product line: Demilec’s Spray Foam Insulation, specifically the Sealection 500 open-cell and Heatlok HFO Pro closed-cell systems, both common in attic retrofits across Harris County. If your home was built or renovated in the last 15 years with Demilec foam, the air sealing component is the foam itself plus the sealant around can lights, plumbing vents, bathroom fan boxes, and top plates. When that foam was applied too thin in spots, or when the sealant bead around a penetration cracks and separates from the framing, you have an air sealing failure even if the foam looks intact from the attic floor.

Here’s what matters for compatibility: Demilec open-cell foam (Sealection 500) is not interchangeable with closed-cell (Heatlok HFO Pro). Open-cell is for interior cavity air barriers and sound control. Closed-cell is what you want against a Houston roof deck because it adds structural strength and stops moisture migration. If a contractor offers to patch open-cell foam with a closed-cell product without verifying the existing material first, walk away. We read the label on the existing foam before we quote anything. One thing that surprises Houston owners: the OEM Demilec product carries a specific density rating printed right on the drum, and a mismatched aftermarket patch can cure at a different rate in our humidity, leaving voids you can’t see until summer hits.

Signs Your Demilec Attic Air Sealing Is Failing

• Upstairs rooms run 5 to 8 degrees warmer than downstairs in July. This is the classic Houston symptom. Hot attic air is leaking in through failed sealant around can lights or top plates, and your AC is fighting a losing battle. The air handler runs longer, the coil works harder, and the upstairs never quite catches up.
• Your electric bill jumped without a rate increase. CenterPoint Energy rates rise, sure. But if you compare kilowatt usage year over year and it’s up 15 to 20%, the likely culprit is conditioned air escaping through gaps that used to be sealed. Open-cell foam loses performance when it gets wet, and in Houston attics, humidity does damage over years, not weeks.
• You can smell attic air in the house. Insulation dust, roof deck heat, the musty smell of a hot attic – if that’s reaching your bedroom, the air barrier has a hole in it. Sealed attics don’t let attic air into living space. Period.
• Pest droppings in the attic near the eaves. Mice and squirrels don’t chew through properly installed closed-cell foam. They do exploit gaps where sealant has cracked away from a vent pipe or a soffit junction. If there’s a critter highway, there’s an air sealing breach at the same spot.
• You can see daylight around can lights from the attic side. This is the easiest check we teach homeowners. Go up in the attic on a bright day with the lights off below. If you see glow around the fixture housings, the sealant has failed and conditioned air is pouring into the attic.

Replacement Cost & What’s Included

In Houston, a Demilec attic air sealing replacement typically runs $1,900 to $3,800. The range comes down to three things: attic size, how many penetrations need re-sealing, and whether the existing foam needs to be cut back before new material goes in. A 1,200 square foot attic with twenty penetrations and the original Demilec foam in decent shape lands near the bottom of that range. A 2,500 square foot attic with water-damaged open-cell foam that needs removal first pushes toward the top.

What’s included in our written price: all labor, all sealant and foam material, removal of failed material that can’t be saved, and disposal. No surprise line items. The number on the written estimate is the number on the invoice. Every air sealing job is covered by our 365-Day Done Right Promise, backed by The Garrison Standard we’ve operated under since 2002. If the work fails within a year, we return at no charge. Written, signed, and specific, not a handshake.

DIY or Call Us?

Here’s the honest split. What an owner can safely check: daylight around can lights from the attic side, visible cracks in the sealant bead around vent pipes, and whether the existing foam feels damp or crumbly. That inspection takes fifteen minutes and tells you whether you need us at all.

What we don’t recommend doing yourself: cutting back failed open-cell foam, attempting to re-spray Demilec material with a rental kit, or using canned spray foam from a hardware store as a permanent fix. Canned foam doesn’t bond to Demilec substrate the way the OEM material does, and in Houston’s humidity, a bad patch job creates a hidden moisture trap. Demilec closed-cell foam also off-gasses significantly during application – proper respirators and ventilation are not optional. The risks of doing it wrong are real, and the material costs for a proper spray rig make a one-off DIY attempt barely cheaper than hiring a crew that does it weekly. If you’ve found failed air sealing, call us at (806) 581-1010 and we’ll give you a straight number before any work starts.

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