Demilec Radiant Barrier Installation: The Fresno Owner’s Guide
Radiant barrier installation for Demilec systems in Fresno typically runs $1,500 to $3,200 installed, and we stock the materials on our trucks so most jobs are done the same week. The barrier itself is a reflective foil layer, usually stapled to the underside of roof rafters, that bounces radiant heat back out before it can soak into your attic insulation. Here’s the honest picture: most Fresno homeowners don’t realize their radiant barrier has failed until August hits and the upstairs rooms feel like an oven no matter how long the AC runs. A sagging, torn, or improperly installed barrier quietly stops doing its job, and your cooling bill climbs because the attic is now baking the insulation below it. The fix is straightforward when you match the right material to the existing Demilec setup, and we’ll get into exactly what that looks like below.
Key takeaways:
- Demilec radiant barrier is designed to work alongside spray foam insulation, not replace it.
- Installed pricing in Fresno depends heavily on attic square footage and access difficulty.
- A failed barrier rarely looks dramatic. Usually it’s subtle: sagging between rafters, torn sections near the eaves, or foil that’s been pulled away from staples.
- Every job we quote gets a written price before work begins, per the Kingswell Guarantee.
Which Demilec Models This Applies To
Demilec doesn’t make a standalone “radiant barrier” product the way Reflectix does. What Demilec produces is spray foam insulation, and the radiant barrier work we do in Fresno is almost always tied to a home that already has Demilec open-cell or closed-cell foam in the attic or walls. The two are complementary: the foam handles conduction and air movement, and the barrier handles radiant heat. If your home has Demilec Heatlok HFO or Sealection 500, you can absolutely add or replace a radiant barrier above it. The key is material choice. We use reinforced foil radiant barrier rated for attic installation, and the thickness matters: single-layer foil is fine for new construction, but we recommend double-layer or foil-faced OSB-style products for retrofits because Fresno attics hit 140-plus degrees in July and the thinner stuff degrades faster. If you have an existing barrier, check the edge printing. If it says “Reflectix,” you have an aftermarket product. If you can’t find any labeling, measure the spacing between rafters before you buy anything. Most Fresno homes built after 1990 run 24-inch on-center rafter spacing, which means you need barrier rolls wide enough to span that gap without sagging.
One compatibility gotcha worth knowing: if you have Demilec open-cell foam already installed at the roofline, you do not add a radiant barrier on top of it. The foam at the deck acts as the thermal boundary, and the barrier goes elsewhere or not at all. Adding foil over open-cell at the roofline can trap moisture. That’s the kind of mistake we see from crews who don’t understand how foam and radiant barriers interact. Glenn Hartley has spent enough time in Fresno attics to spot this in about 30 seconds, which is why our quotes start with a look at what’s actually up there, not a guess over the phone.
A note on affiliation: Woolsey Insulation Fresno is an independent service provider. We install and service radiant barrier systems that work with Demilec products, but we’re not affiliated with Demilec.
Signs Your Demilec Radiant Barrier Installation Is Failing
- Upstairs rooms are noticeably hotter than downstairs, even with AC running. Radiant heat gets through. The barrier’s whole job is to reflect that heat, and when it fails, the attic becomes a heat battery that cooks your ceilings.
- Visible sagging or drooping between rafters. Fresno heat cycles cause staples to work loose over years, especially in homes with unvented attics. Once the foil isn’t taut, it loses reflectivity and you get air gaps where heat pours through.
- Tears, punctures, or water staining on the foil. Roof leaks, pest activity, and careless contractors walking the rafters during other work all damage barriers. A torn section reflects almost nothing. Water staining means the foil’s low-emissivity surface has oxidized.
- Dust buildup on the foil surface. Radiant barriers work by reflecting, and a thick layer of dust kills that. This is a big one in Fresno, where summer dust from the surrounding farmland drifts into attic spaces quickly. A barrier installed five years ago may be covered in a fine layer of valley dust if the attic vents weren’t filtered.
- Cooling bills creeping up year over year without other explanation. This is the slow-failure signal. You won’t see it, but your utility statement will. If the insulation below the barrier is Demilec foam, that foam is now absorbing the radiant load the barrier used to deflect.
Replacement Cost & What’s Included
Here’s what a Demilec-compatible radiant barrier replacement actually costs in Fresno. To be clear about the price, the table below shows what we quote based on what we find when we look first. These are installed prices, not material-only.
Fresno Radiant Barrier Replacement Pricing
- Small attic, good access (up to 800 sq ft): $1,500 – $1,900
- Standard suburban attic (800 – 1,500 sq ft): $1,900 – $2,600
- Large or difficult attic (1,500 – 2,500 sq ft): $2,600 – $3,200
- Removal of failed existing barrier: $200 – $400 added, depending on how much is hanging and how big the attic is.
What’s included: full attic inspection first, written quote with the exact installed price, removal of the old barrier if needed, new reinforced reflective barrier stapled to rafters per manufacturer spacing, and the Kingswell 365-Day Done Right Promise, in writing, on every job. If the installation isn’t right within 365 days, we come back and fix it at no charge. Same deal as our installation work: a written price before any work begins, no door-step changes. Background-checked, uniformed technicians handle the work, and a live person answers the phone 24/7 if you have a question before, during, or after.
DIY or Call Us?
Radiant barrier itself isn’t dangerous the way gas lines or high-tension springs are. You’re not going to lose a finger working with foil. But the attic environment in Fresno is something we take seriously. A summer attic can hit 140 degrees, and working up there without proper ventilation and hydration is how people end up in the hospital. The real risk isn’t the part; it’s the space you’re installing it in. What you can safely do yourself: check the attic from the access hatch with a flashlight, look for obvious sagging or tears, and take photos. What tends to go wrong with DIY barrier replacement: you buy a one-layer foil that sags within a year, you staple it too tight and it tears at the fasteners, or you miss that your existing barrier is fine and your problem is actually the insulation underneath it. We’ve seen homeowners spend a weekend in the attic installing a $400 roll of foil over insulation that needed to be replaced entirely. If you’re up there and something doesn’t look right, call (559) 785-2658 before you buy anything. We’ll tell you what you’re looking at, honestly, even if the answer is “your barrier is fine.”
FAQs
A properly installed reinforced radiant barrier in Fresno lasts 10 to 15 years. Single-layer foil tends to fail faster, usually in 5 to 8 years because Fresno’s summer heat and valley dust degrade the reflective surface. If your barrier is older than a decade, it’s worth a look before next summer. Call (559) 785-2658 and we’ll inspect it.
Small tears under a foot long can usually be patched with foil tape rated for attic use, but sagging or dust-damaged sections almost always need replacement. The repair-versus-replace call depends on what we see when we’re up there. We’ll tell you straight either way.
Most Fresno homes take one day. We set an arrival window before work starts, per the Kingswell Guarantee, and the crew usually finishes a standard attic in four to six hours. Larger homes or tricky access points push it to a second day, and we’ll tell you that before we start.
We stock reinforced radiant barrier on our trucks, along with materials compatible with the eight brands we work with: Owens Corning, Johns Manville, Knauf, Rockwool, CertainTeed, Icynene, Demilec, GreenFiber, and Reflectix for aftermarket barrier work. The material we recommend depends on your attic and what’s already installed, not what happens to be on the truck that day.
Ready to get a written price?
If your Fresno home has a failing radiant barrier, or you suspect the one up there isn’t doing its job, call (559) 785-2658. A live person answers, 24 hours a day, 7 days a week. We’ll schedule a look at the attic, give you a written installed price before any work begins, and put the guarantee in writing. Look before you quote. Every attic tells you something the paperwork won’t.
Written by Glenn Hartley, Owner, Woolsey Insulation Fresno at Woolsey Insulation Fresno, serving Fresno and nearby areas.