Demilec Attic Insulation Nationwide

Demilec Attic Insulation: The Seguin Owner’s Guide

Demilec attic insulation replacement in Seguin typically runs $2.80-$4.50 per square foot installed for open-cell spray foam, or $4.20-$6.80 for closed-cell, with most residential attic jobs falling between $3,200 and $7,800 depending on thickness and square footage. We stock Demilec-compatible formulations on our truck and can usually inspect and quote same-day. Most Seguin homeowners discover their Demilec insulation is failing when they notice the second floor won’t cool below 78°F in July, or when they find condensation staining the drywall around attic hatches in winter - signs that the foam has separated from the deck, shrunk, or was installed at the wrong lift thickness to begin with.

Call (830) 549-6646

Which Demilec Models This Applies To

Demilec produces several spray foam lines that appear in Seguin attics, and identifying which one you have determines what we can do next. The most common is Heatlok HFO High Lift, identifiable by a light yellow color and a density around 0.5 lb/ft³ for open-cell; closed-cell Heatlok XT runs gray at 2.0 lb/ft³. Check the spray foam surface for a stamped or stickered lot number - usually found on a tag left by the original installer near the attic access or on the rim joist. If you see Demilec SEALECTION 500, that’s an older open-cell formulation from the early 2010s; it’s not made anymore, but we match it with current Heatlok open-cell that bonds to the old substrate.

The compatibility gotcha in Seguin: Demilec’s HFO-blown foams require specific substrate temperatures at application (minimum 60°F surface temp, per Demilec’s published data). We’ve found original installs done in December or January where the crew sprayed over cold OSB, and the foam never achieved full adhesion. You can’t fix that with more foam on top - the failed layer has to come out or be mechanically secured first. We also stock Reflectix radiant barrier as a hybrid option for homeowners who want to supplement rather than replace.

Topside Attic Insulation Seguin is an independent service provider - not affiliated with Demilec - and we source formulations from Demilec, Icynene, and other manufacturers based on what the job actually needs.

Signs Your Demilec Attic Insulation Is Failing

• Hot second floor despite new HVAC equipment. The compressor runs constantly but can’t pull the upstairs below 76-78°F. What we usually find: the Demilec open-cell has pulled away from the roof deck at the ridge, creating a convection channel that bypasses the foam entirely. The insulation R-value hasn’t changed, but the air barrier is gone.
• Condensation or water staining on ceiling drywall below the attic. In Seguin’s humid shoulder seasons, warm moist air hits the cold ductwork or drywall where the foam has shrunk or cracked. The foam itself isn’t wet - it’s the gap that lets air reach the cold surface.
• Visible yellowing, powdering, or crumbling at the foam surface. Demilec open-cell can degrade if exposed to ultraviolet light through a gable vent or missing soffit screen. The UV breaks the polymer bonds, and the foam turns to dust you can sweep up with a broom.
• Uneven texture with “waves” or pockets between lifts. Proper Demilec application requires passes no thicker than 2-3 inches per lift, with a gel time between passes. Rushed installs create voids you can’t see until you probe with a wire. We document these with photos and mark them on your report.
• Rodent disturbance or nesting in the foam. Spray foam isn’t rodent-proof - mice will tunnel through open-cell for nesting material. In Seguin’s older neighborhoods near Guadalupe Regional Medical Center, we’ve found extensive tunneling in 1970s attics where the original fiberglass was removed and replaced with Demilec, but the entry points were never sealed. The foam is intact; the air sealing is not.

Before

After

Replacement Cost & What’s Included

Every Demilec replacement we quote includes: removal of non-bonded or degraded foam, mechanical fastening of any delaminated areas that can be saved, full air sealing of top plates, can lights, and plumbing/electrical penetrations, then new foam installed to the specified thickness with documented pass counts. We run a blower-door test before and after - a pressurization reading that shows, in one number, how much air your building envelope was losing - and you get the printed report with ACH50 numbers. Under Haven Standard Clause 1, you get a written price before any work starts, a written scope, and a written warranty. The 365-Day Done Right Promise applies to all completed work.

DIY or Call Us?

There’s no safe DIY for spray foam installation - the two-part chemicals require respirators with organic vapor cartridges, full skin coverage, and controlled ventilation that a residential attic doesn’t provide. The isocyanate component is a potent sensitizer; once you’re sensitized, you can’t be around it again. We’ve seen homeowners try to fill gaps with canned “touch-up” foam, which is fine for a quarter-inch crack around a light fixture but useless for a 40-square-foot delamination at the ridge.

What you can safely check: look for the lot number tag, photograph any visible gaps or discoloration, and note whether your upstairs temperature problem is new or seasonal. Don’t poke the foam with a screwdriver - you can’t tell density or adhesion that way, and you’ll create an entry point for moisture. Call (830) 549-6646 and we’ll read what you’ve found. Estimates are free, and we bring a written price to the visit.

FAQs