Demilec Radiant Barrier Installation: The Morgan Hill Owner’s Guide
Demilec radiant barrier installation in Morgan Hill typically runs $2,800-$4,600 for a standard 1,800-2,400 square foot attic, and we stock the full Demilec-compatible line for same-day starts on most jobs. Most homeowners realize something’s off when their upstairs bedrooms won’t cool below 78°F even after the AC runs all afternoon, or when their summer electric bills spike $80-$140 above the previous year despite no rate change. We see this pattern constantly in Morgan Hill’s south Santa Clara County climate, where attic temperatures regularly hit 140-160°F and a degraded or missing radiant barrier turns your ceiling into a slow cooker.
Which Demilec Models This Applies To
Demilec’s radiant barrier products fall under their broader spray-foam and building-envelope catalog, specifically the Heatlok HFO and Demilec 500 series installations where a reflective component was specified as part of the thermal control layer. If your original install was 2015-2022, check your attic for the silver reflective facing - Demilec used both foil-faced polyiso boards and loose reflective sheeting depending on the contractor’s spec. The critical compatibility gotcha: Demilec’s early foil-faced assemblies were 48-inch width only, while post-2018 jobs often switched to 51-inch rolls to reduce seam count. We measure on site before ordering, because ordering the wrong width means taping an extra 15-20 linear feet of seams, and every seam is a future failure point. Topside Attic Insulation Morgan Hill is an independent service provider with no affiliation to Demilec; we source Demilec-compatible materials through our normal supply chain alongside Owens Corning, Johns Manville, and Reflectix equivalents.
For OEM-versus-aftermarket on radiant barrier specifically, the honest answer is that the reflective aluminum layer itself is commodity-grade in most cases. Where Demilec’s original spec mattered was the substrate - kraft-faced fiberglass, polyiso, or direct-to-deck application. We match that substrate to the existing assembly rather than chasing a brand name, because a mis-matched substrate delaminates in 3-5 years in Morgan Hill’s heat-cycling attic environment.
Signs Your Demilec Radiant Barrier Installation Is Failing
- Hot ceiling patches in late afternoon. The radiant barrier’s aluminum surface oxidizes or accumulates dust over time, dropping reflectivity from 95% to 60% or lower. In Morgan Hill, where agricultural dust from the surrounding valley gets pulled into attic vents, we see this degradation accelerate after year six or seven.
- AC runs continuously from 2 PM to 8 PM in July and August. A functioning radiant barrier should reduce radiant heat transfer through the ceiling by 40-50%. When that drops, your ductwork - especially if it’s in the attic - is fighting 150°F air instead of 110°F air.
- Visible tears, gaps, or sections lying on the insulation below. Demilec installations stapled to rafters can sag if fasteners corrode in humid attic conditions. Once the barrier contacts the insulation, it’s conducting heat instead of reflecting it.
- New or worsening temperature stratification between floors. A 12-15°F difference between your downstairs thermostat and upstairs bedrooms was normal before; now it’s 18-25°F. The barrier isn’t doing its job of keeping ceiling surface temperatures down.
- Insulation that looks darker or compressed directly below the barrier. Heat baking the top layer of insulation degrades its R-value permanently. We’ve pulled R-38 batts in Morgan Hill that tested at R-22 because years of radiant overload cooked the fibers.
Replacement Cost & What’s Included
| Component | Price Range (Morgan Hill) |
|---|---|
| Demilec-compatible radiant barrier material (per sq ft) | $1.40-$2.10 |
| Attic air sealing (top plates, penetrations, can lights) - prerequisite | $680-$1,200 |
| Labor for barrier installation | $1,400-$2,200 |
| Before-and-after blower-door test | Included |
| Documented Photo Record | Included |
| Total typical installed cost, 1,800-2,400 sq ft attic | $2,800-$4,600 |
The range depends on three things: attic accessibility (truss spacing, existing storage platforms we need to work around), whether we’re replacing degraded insulation beneath the barrier, and how much air sealing the top plates and penetrations need before the barrier goes in. We don’t quote radiant barrier without the air sealing - Seal the leaks first. The insulation just holds what you’ve already captured. Every job closes with a written scope, written warranty, and your blower-door numbers before and after.
DIY or Call Us?
There’s no high-tension danger with radiant barrier like there is with garage door springs or gas lines, but the failure mode of DIY is performance theater - it looks right and does almost nothing. Homeowners can safely check whether sections have fallen, whether fasteners are intact, and whether dust accumulation is visible. What goes wrong in DIY replacement: seams taped with the wrong adhesive that fails at 140°F, barrier installed with gaps that let radiant heat straight through, or - most common - barrier installed over an unsealed attic floor so conditioned air leaks straight past it. Wes Okafor learned at Olive-Harvey College that the blower door doesn’t lie, and we’ve tested Morgan Hill attics where a homeowner’s weekend barrier job dropped the radiant heat transfer by maybe 10%. The material was fine. The execution wasn’t. Call (669) 280-8103 and we’ll read your existing setup with you, no charge for the assessment.
FAQs
In Morgan Hill’s hot-dry summers and mild wet winters, a properly installed radiant barrier lasts 15-25 years before reflectivity degrades below useful levels. Dust accumulation from valley agriculture and nearby construction is the real killer; we’ve seen barriers lose effectiveness in 8-10 years when attic ventilation pulls in particulates that coat the aluminum surface. Call (669) 280-8103 for an attic inspection - estimates are free.
Small tears and detached sections can be patched or re-fastened if the surrounding material is still reflective, but widespread oxidation, delamination, or sagging means full replacement. We don’t quote patch jobs on barrier that’s past 60% of expected lifespan - it’s cheaper long-term to do it once. Call (669) 280-8103 and we’ll show you the thermal images so you can decide.
Most Demilec-compatible radiant barrier replacements in Morgan Hill take one full day for crews of two, assuming the attic is accessible and we’ve completed air sealing the day before or that morning. Larger attics or those with extensive storage platforms to work around may run into a second day. We give you a written schedule with your written price - no surprises.
We stock 48-inch and 51-inch reflective barrier rolls compatible with Demilec specifications on our Morgan Hill warehouse truck, plus the specialized high-temp tapes and fasteners that don’t fail in attic heat. For non-standard substrates or unusual truss spacing, we can have materials next business day. Call (669) 280-8103 to confirm stock for your specific attic dimensions.
Written by Wes Okafor, Owner & Lead Insulation Technician, Topside Attic Insulation Morgan Hill at Topside Attic Insulation Morgan Hill, serving Morgan Hill and nearby areas.