Johns Manville Radiant Barrier Installation: The Leander Owner’s Guide
We install Johns Manville-compatible radiant barrier systems in Leander homes for $1.80 to $2.40 per square foot of attic deck, with most single-story jobs landing between $1,400 and $2,200 and two-story or complex rooflines running $2,400 to $3,600. Same-day installation is available when we have your roof geometry on file from a prior energy audit or photo set. Most Leander homeowners discover their radiant barrier is failing when upstairs rooms won’t cool below 78°F despite the AC running continuously, or when they spot the original kraft-facing turning to dust after a decade of 140°F attic summers.
Which Johns Manville Models This Applies To
Johns Manville produces radiant barrier products under two distinct lines that we encounter in Leander attics: the AP Foil-Faced Polyiso board stock (typically 1/2-inch and 1-inch thicknesses with a labeled R-value of 3.0 and 6.0 respectively) and the ComfortTherm batts with factory-applied radiant barrier facing. The critical identification point is the foil stamp: AP Foil-Faced carries a Johns Manville logo and ASTM C1289 compliance marking; ComfortTherm batts show a directional arrow indicating which side faces the conditioned space.
The compatibility gotcha in Leander’s 2015-2022 build stock is this: some builders installed AP Foil-Faced board directly against roof decking without the required 3/4-inch minimum air gap, which voids the radiant barrier performance and traps moisture against the sheathing. We’ve pulled dozens of these in Crystal Falls and Travisso where the foil has delaminated and the OSB beneath has begun to crown. For replacement, we stock Johns Manville AP Foil-Faced in 4×8 sheets and can source ComfortTherm with 48-hour lead time; we also carry Reflectix double-bubble product as a quality aftermarket alternative when the original JM spec has been discontinued or when the homeowner wants a rolled-goods installation rather than rigid board.
Topside Attic Insulation Leander is an independent service provider, not affiliated with Johns Manville.
Signs Your Johns Manville Radiant Barrier Installation Is Failing
- Upstairs rooms stay hot past 9 p.m. - The radiant barrier’s emissivity has degraded above 0.05 (the functional threshold), meaning it’s no longer reflecting infrared radiation back toward the roof deck. In Leander, this typically happens after 8-12 years of UV exposure through gable vents or degraded ridge vent screening.
- Foil facing is flaking, chalking, or peeling in sheets. - This is oxidation of the aluminum layer, accelerated by attic humidity cycling. We see this most often in homes near the San Gabriel River corridor where nighttime cooling drives condensation against the foil.
- Visible water staining on the foil surface or roof decking beneath. - The barrier has become a vapor retarder in the wrong location, trapping moisture that should have escaped. This is almost always an installation-sequence error from the original builder, not a material defect.
- Insulation beneath the barrier is compressed or displaced. - Failed radiant barrier installations often sag or detach, falling onto blown fiberglass below and compressing it to half its labeled thickness. An R-38 compressed to R-19 is functionally worthless.
- Energy bills spike in July-August with no rate change. - When the radiant barrier stops working, attic temperatures climb from a managed 110-120°F to 140-150°F, forcing the duct system to absorb that heat load. We document this with FLIR imaging; the temperature delta across a failed barrier is usually 25-35°F.
Before
AfterReplacement Cost & What’s Included
| Scope | Price Range (Leander) |
|---|---|
| Single-story, open attic, up to 1,500 sq ft deck | $1,400 - $2,200 |
| Two-story or complex roofline, 1,500-2,500 sq ft | $2,400 - $3,600 |
| Air sealing package (top plates, can lights, penetrations) | $400 - $800 additional |
| Blower-door test with documented before/after | Included on all jobs |
What drives the range: roof pitch (steeper = more labor), existing insulation that must be removed or worked around, and whether the original installation left the air gap intact or created moisture damage requiring decking repair. Every job includes removal of failed material, installation of new Johns Manville or Reflectix product with proper air gap maintenance, and a Documented Photo Record showing before, during, and after. On jobs where we perform air sealing, we provide before-and-after blower-door numbers so you can verify the envelope performance change. The 365-Day Done Right Promise applies; if emissivity testing or visual inspection shows material failure within that window, we replace at no charge.
DIY or Call Us?
There’s no high-tension danger in radiant barrier work, but there are two ways DIY goes wrong in Leander attics. First, the air gap: stapling foil directly to roof decking without the required 3/4-inch minimum space kills performance and voids manufacturer warranty. Second, working in 140°F attic air in July is genuinely hazardous; heat exhaustion hits fast when you’re kneeling on joists 15 feet above a garage floor.
What you can safely check from the hatch: look for flaking foil, sagging sections, or dark water stains. If you see any of these, call us at (737) 252-7159 and we’ll bring a thermal imager and a written price before any work starts. We stock Johns Manville AP Foil-Faced on the truck for same-day replacement when the scope is straightforward.
FAQs
In Leander’s climate, properly installed Johns Manville radiant barrier maintains effective emissivity for 10 to 15 years. Attics that see sustained 140°F summers with poor ventilation compress that to 8 years, which is what we regularly measure in Crystal Falls and the older sections of Leander. Call (737) 252-7159 for a free estimate if you’re past the decade mark.
Localized patching is possible if less than 10% of the surface has failed and the remaining foil passes emissivity testing. In practice, we replace 90% of what we inspect because oxidation spreads unevenly and patched sections create thermal bridges that show up on FLIR. We don’t charge to evaluate; call (737) 252-7159 and we’ll tell you honestly which category you’re in.
Most single-story Leander homes take one crew day; two-story or complex rooflines with multiple attic zones take two days. We don’t start until you have a written scope and written price in hand, and we don’t leave until the Documented Photo Record and blower-door numbers are in yours. Call (737) 252-7159 to schedule.
We carry Johns Manville AP Foil-Faced 1/2-inch and 1-inch board stock on every Leander truck, plus Reflectix double-bubble as an alternative. ComfortTherm batts require 48-hour lead time. If your original installation used a discontinued JM SKU, we’ll match the thermal performance spec and show you the comparison data before we install. Call (737) 252-7159 to confirm availability for your job.
Written by Wes Okafor, Owner, Topside Attic Insulation Leander at Topside Attic Insulation Leander, serving Leander and nearby areas.