Demilec Radiant Barrier Installation Nationwide

Demilec Radiant Barrier Installation: The Seguin Owner’s Guide

Demilec radiant barrier installation in Seguin typically runs between $1,800 and $3,400 for a standard 2,000-square-foot attic, and we stock Demilec-compatible radiant barrier materials on our trucks for same-day starts. Most Seguin homeowners discover their radiant barrier is failing when upstairs rooms won’t cool below 78°F even after the AC runs all afternoon, or when they notice the original foil has torn away from rafter staples after a few Hill Country hail seasons. We see this pattern regularly in neighborhoods near Guadalupe Regional Medical Center, where attics built in the 1970s and 1980s were retrofit with early radiant barrier products that weren’t designed for our UV load and temperature swings.

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Which Demilec Models This Applies To

Demilec produces radiant barrier coatings under their Heatlok and SEALECTION product families, plus standalone foil and spray-applied barrier systems sold through regional distributors. The critical identification step is reading the original application label, usually found on a rafter tag or in the homeowner’s insulation documentation from the original install. Demilec’s spray-applied radiant barrier coatings are typically 1 to 2 mils dry film thickness and are compatible with their open-cell and closed-cell foam substrates, but they will delaminate if applied directly over dusty or unprimed OSB.

We carry both OEM-spec Demilec coatings and equivalent-performance aftermarket barriers from Reflectix for homeowners who want a mechanical foil alternative. The aftermarket route makes sense when the original Demilec application was part of a broader foam job and the homeowner only needs the radiant barrier layer refreshed. We’ve learned that Demilec’s coating chemistry bonds poorly to surfaces previously treated with oil-based wood preservatives, a compatibility gotcha we check for during our attic inspection. For Seguin homes with original Demilec installs from 2012 to 2019, we verify whether the substrate is their legacy polyicyanurate board or the current spray-foam-compatible formulation, because the primer requirements differ.

Signs Your Demilec Radiant Barrier Installation Is Failing

• Upstairs rooms run 8 to 12 degrees warmer than downstairs by late afternoon. The radiant barrier’s emissivity has degraded, meaning it’s no longer reflecting infrared heat back toward the roof deck. In Seguin’s summer sun load, a barrier that tests above 0.15 emissivity is functionally done, and we measure this with a handheld infrared thermometer during our inspection.
• Foil sheets are sagging, torn, or missing from staple lines. Demilec’s mechanical foil products rely on corrosion-resistant staples and proper tension, but our humidity swings cause expansion cycling that pops staples loose. Once the foil loses contact with the rafter, it becomes a convection trap instead of a reflector.
• Spray-applied coating is chalking, flaking, or showing bare substrate. UV degradation of the acrylic or aluminum-pigmented binder breaks down the surface. We see this accelerate in west-facing attic planes where roof temperatures in Seguin regularly hit 140°F plus.
• Energy bills spike in July and August with no rate change. A failed radiant barrier forces your AC to run longer to overcome radiant heat gain. When we blower-door test homes with compromised barriers, the cooling load calculation often shows 15 to 25 percent more tonnage demand than the same home with intact barrier.
• You see water staining on the barrier surface after heavy rain. This indicates a roof leak, but it also means the barrier is trapping moisture against decking instead of allowing diffusion. Demilec spray barriers are vapor-permeable when intact, but damaged areas create localized condensation points.

Before

After

Replacement Cost & What’s Included

What drives the range: attic accessibility (scissor truss vs. conventional), whether we need to remove failed material first, and whether the substrate requires primer or repair. Every Demilec radiant barrier installation we quote includes the barrier material, fasteners or spray application, cleanup, and our Documented Photo Record. On jobs where air sealing is applicable, we run a blower-door test before and after, and the report goes home with you - the numbers do the talking. The 365-Day Done Right Promise covers all work, and your written price is locked before anyone enters the attic.

DIY or Call Us?

There’s a safe middle ground and a hard stop. Homeowners can check their attic access panel for the original Demilec documentation, photograph any visible labeling, and verify with a non-contact thermometer whether roof deck temperatures exceed 130°F on a 95°F day. These steps help us diagnose over the phone.

Where DIY goes wrong: spray-applied radiant barriers require respiratory protection, forced ventilation, and precise mil-thickness application. Too thin and you get no performance; too thick and the coating cracks. Mechanical foil installation in Seguin’s heat means working on rafters that burn skin on contact, and improper staple spacing creates sagging that voids the barrier effect within two seasons. We don’t recommend owner installation of either system. Call (830) 549-6646 and we’ll walk through what we found on our last Seguin job with a similar Demilec setup.

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