Demilec Radiant Barrier Installation: The San Antonio Owner’s Guide
Demilec radiant barrier installation in San Antonio typically runs $0.85 to $1.50 per square foot installed, and we keep Demilec-compatible radiant barrier on our trucks for same-day or next-day service across Bexar County. Most homeowners discover their radiant barrier has failed when their August electric bill spikes and the attic feels like a furnace at noon. You might also spot sagging foil, torn sections, or gaps where the barrier pulled away from the rafters. If you’re standing in the attic sweating through your shirt while the AC runs full blast downstairs, the barrier isn’t doing its job anymore. That’s the call we get most often, and it’s a straightforward fix when you’ve got the right material and a crew that knows how San Antonio attics behave in July.
Key Takeaways:
- Demilec radiant barrier installation costs $0.85 to $1.50 per square foot in San Antonio, depending on attic access and existing insulation condition.
- We stock Demilec-compatible radiant barrier sheets and can usually install same-day or next-day.
- Radiant barriers in South Texas heat typically last 10 to 15 years before the foil delaminates or tears away from the substrate.
- Installation is not a safe DIY project on a hot day: attic temperatures above 120°F cause heat exhaustion fast, and working around trusses and wiring in tight spaces requires care.
- Every job is covered by our lifetime Done Right Promise, and we answer the phone live 24/7.
Which Demilec Models This Applies To
Demilec radiant barrier products come in a few configurations, and the installation approach depends on which one you have. The two most common in San Antonio homes are the single-sided foil laminate, typically stapled to the underside of roof rafters, and the double-sided foil used in open attics where reflection matters on both faces. Demilec’s radiant barrier is designed to work alongside their open-cell and closed-cell spray foam lines, which matters because the barrier and the foam have to be installed in the right sequence. We’ve seen attics where someone foamed first and then tried to retrofit a radiant barrier, and the result was trapped moisture against the roof deck. On the north side near Stone Oak and in older neighborhoods like Alamo Heights, the roof pitch and truss spacing vary enough that one-size-fits-all installs don’t hold up. When we spec a Demilec radiant barrier for a San Antonio house, we measure the rafter bays before quoting so you’re not paying for material that gets cut to scraps.
OEM versus aftermarket is a fair question with Demilec. We use Demilec-compatible radiant barrier that meets the same reflectivity spec, which is 97% for clean, unoxidized foil. The aftermarket equivalent is indistinguishable in performance and typically costs less. Where OEM matters more is when you’re matching a warranty claim on a newer Demilec insulation system. In that case, we’ll use the branded product and document everything. We’re an independent installer, not a Demilec affiliate, so our recommendations are based on what holds up in this climate, not on what a manufacturer wants us to push. Reflectix is another brand we stock for retrofits where a thinner, more flexible barrier makes sense, usually around ducts and garage ceilings.
Signs Your Demilec Radiant Barrier Installation Is Failing
- Sagging or drooping foil between rafters. The adhesive backing on Demilec’s foil degrades in sustained attic heat, and once the foil sags more than an inch or two, the air gap that makes it work collapses. Heat transfer jumps immediately.
- Visible oxidation or dulling on the foil face. Radiant barrier works by reflecting radiant heat, and a dull, cloudy surface is oxidized foil. Reflectivity drops from 97% into the low 80s, which translates to a warmer attic and a harder-working AC.
- Tears or punctures where the barrier was walked on. Cable installers, HVAC techs, and pest control visits can damage the foil. Any puncture larger than a fist compromises the barrier’s continuity. We see this most in San Antonio neighborhoods with older homes that have had repeated service visits over the years.
- Staples pulling out of the rafter wood. South Texas heat dries out lumber over time, and older installs with narrow-crown staples fail at the fastener points. You’ll see the barrier hanging by a thread in one corner and fully detached in another.
- Higher summer bills with no change in household habits. If you track year-over-year June through September usage and it’s up 15 to 20 percent with the same thermostat settings, a failed or underperforming radiant barrier is one of the first places we look.
Replacement Cost & What’s Included
Installed Demilec-compatible radiant barrier in San Antonio runs between $0.85 and $1.50 per square foot. A typical 1,800-square-foot attic with moderate roof pitch lands around $1,500 to $2,700 total. What moves the price: attic access (pull-down stairs versus a scuttle hole in a closet), roof pitch, how many obstacles we have to cut around, and whether the old barrier needs removing first. Some companies quote labor-only and stick you with a material surprise at the end. We don’t. The price we quote is the price you pay: material, fasteners, cleanup, and the full installation. Every measurement is taken before we write the number, so there’s no guesswork. And every radiant barrier install carries our lifetime Done Right Promise. If it’s not done right the first time, we come back and make it right. No invoice, no argument. That’s been our standing rule since 2000 when I started this business because I got tired of watching San Antonio homeowners get burned by vague quotes and disappearing contractors. $40 off any repair over $200 applies here, and seniors and veterans always get 10 percent off. Always.
DIY or Call Us?
If you just want to see whether your Demilec radiant barrier is failing, you can do a visual check from the attic access point with a flashlight. Look for sagging, tears, and dull foil. That’s safe. What’s not safe is working in a San Antonio attic between May and September. Attic temperatures routinely hit 140°F in the afternoon, and that’s heat exhaustion territory within 15 minutes. Working on a roof deck means balancing on trusses, handling staple guns at awkward angles, and navigating around wiring you can’t always see. We’ve had customers try it and call us halfway through, sunburned and frustrated, having bought the wrong width barrier or run out of staples at the worst moment. If your attic is cool enough to work in and you know the rafter measurements exactly, a straightforward single-run install is possible. But for a full retrofit with old barrier removal and proper seam overlap, call us at (866) 751-4428. We’re local, we answer the phone live, and we’ll give you a straight answer on whether this is a job you should take on or one we should handle for you.
FAQs
A properly installed Demilec radiant barrier lasts 10 to 15 years in South Texas heat before the foil surface oxidizes enough to matter or the fasteners start letting go. Attic conditions, roof ventilation, and whether the original installer used vapor-permeable fastening practices all affect lifespan. Call (866) 751-4428 if you want us to look at yours and give you an honest assessment.
Small tears under a foot long can be patched with foil tape, but the patch reflects less heat than the original surface and will eventually peel in high heat. For larger damage or multiple failure points, replacement makes more sense than chasing patches year after year. We’ll tell you which is worth your money either way.
Most Demilec radiant barrier installations in San Antonio take four to six hours for a typical single-story home, including old barrier removal if needed. Two-story homes or attics with complex roof geometry can run a full day. We schedule around your availability and show up when we say we will.
We stock Demilec-compatible radiant barrier in the sizes that fit most San Antonio homes, so we usually don’t need to order anything special. If your attic requires a non-standard width or you need OEM Demilec product for warranty purposes, we’ll source it and get it on the schedule quickly.
Call us at (866) 751-4428 for a free estimate on Demilec radiant barrier installation. We answer the phone live, talk to a real person, and get you a straight answer. No trip charge inside our service county, and a free second opinion on any written estimate you’ve gotten from another company.
Written by Walt Brenner, Owner, Walt’s Insulation at Walt’s Insulation, serving San Antonio and nearby areas.