Johns Manville Radiant Barrier Installation: The San Antonio Owner’s Guide
We stock and install Johns Manville radiant barrier in San Antonio, with most whole-attic installations running between $1,800 and $3,400 depending on square footage and roof pitch. Our crew typically completes a standard single-story radiant barrier job in one day, and you’ll have a written price before anyone opens the attic hatch. Most San Antonio homeowners call us after noticing upstairs rooms that won’t hold a cool temperature, or after pulling down the attic ladder in July and feeling heat radiating onto the back of their neck like an open oven door.
Here’s the reality: San Antonio’s attic temperatures regularly climb past 140°F in July and August. A Johns Manville radiant barrier reflects that heat back toward the roof deck before it ever reaches your insulation. When the barrier is installed wrong, torn, or missing in sections, your insulation ends up fighting heat it should never have seen in the first place.
Which Johns Manville Models This Applies To
Johns Manville manufactures radiant barrier in two primary configurations: the perforated single-layer foil (typically the R-0.7 line sold as a standalone attic product) and the foil-faced OSB sheathing panels used in new construction. The retrofit market in San Antonio almost always involves the single-layer perforated foil, which gets stapled to the underside of the roof rafters. Perforation matters more than most homeowners realize. Those tiny holes allow water vapor to pass through, which prevents condensation from building up between the foil and the roof deck during our humid Gulf-adjacent winters. Non-perforated foil installed in a San Antonio attic will trap moisture and eventually cause deck rot.
When we arrive for an estimate, we check three things before quoting: the roof pitch, the rafter spacing, and whether a previous contractor left partial coverage. The foil comes in 26-inch and 50-inch widths, with the wider rolls saving labor time on 24-inch on-center rafter spacing. Johns Manville’s product spec calls for a minimum 1-inch air gap between the foil and the roof deck, so cathedral ceilings and attics with spray foam against the deck are not candidates for this retrofit. We’ll tell you that on the phone before you ever pay for an estimate call.
We install genuine Johns Manville foil and also stock Reflectix as a like-spec alternative where a homeowner has an existing partial Reflectix install and wants matching product. We’re an independent San Antonio installer, not affiliated with Johns Manville, which means we tell you which product actually fits your attic rather than pushing one brand over another.
Signs Your Johns Manville Radiant Barrier Installation Is Failing
- Upstairs rooms run 5 – 8°F warmer than downstairs, even with the AC running hard. The barrier has either sagged away from the rafters, lost its staple points, or was never installed over the full roofline. Heat pours through the gaps directly onto your insulation layer.
- The foil is tarnished, dull, or coated in dust. Radiant barrier works by reflecting infrared heat, and a layer of dust acts like a blanket over a mirror. In San Antonio’s dry, dusty summers, unsealed attics collect grime fast. If the foil doesn’t shine, it doesn’t reflect.
- You see tears, ripples, or areas where the foil hangs loose. High winds during spring storms can get into a vented attic and flutter unsecured foil until staple points tear through. Once the foil sags, the required air gap closes and the barrier stops doing its job.
- Your attic shows condensation stains or damp insulation near the roof line. This is the perforated-versus-non-perforated failure. The wrong product trapped moisture, and now the roof deck is sweating. This is the one failure mode that can cause structural damage if ignored.
- Energy bills creep up every summer despite no change in household habits. A radiant barrier that was working will cut attic heat gain by 15 – 25%. When it stops working, your AC runs longer to hit the same set point. That shows up on the CPS Energy bill by August.
Replacement Cost & What’s Included
For a typical San Antonio single-story home between 1,500 and 2,200 square feet, a full Johns Manville radiant barrier installation runs $1,800 to $3,400. Steeper roofs, tight attics with limited working clearance, and partial removal of old failed foil push costs toward the upper end. The foil itself runs roughly $0.30 to $0.55 per square foot for the material; the rest is labor, because someone has to work in a 140°F attic and staple foil to rafters without skipping rows or leaving sags.
Every quote from us includes removal and disposal of failed or partial foil, full coverage per Johns Manville’s installation spec with the proper 1-inch air gap, and cleanup. You get the written number before we start, and the 365-Day Done Right Promise stands behind the work. If it’s not right, we make it right. No debate, no fine print.
DIY or Call Us?
You can safely do the diagnosis yourself: check whether foil is sagging, torn, missing in sections, or coated in dust. That’s a flashlight-and-ladder job. What we don’t recommend is the installation itself. Working in a San Antonio attic between June and September means temperatures well over 120°F, and heat exhaustion comes on fast. Beyond the heat, staple placement matters. Stapling too close to the roof deck cuts off the air gap, too few staples and the foil sags within a year, and nicked wiring or punctured ductwork becomes a new problem you didn’t have before.
If you want the foil up and done right the first time, call us at (903) 437-9164. We’ll measure, quote, and schedule around your family’s routine. Quiet tools if there’s a napping baby, shoe covers from the front door to the attic hatch, and a photo of the cleaned-up attic before we leave.
FAQs
A properly installed perforated foil radiant barrier will last 15 to 20 years in a San Antonio attic before the reflective surface degrades enough to matter. The limiting factor here is dust accumulation and staple failure, not the foil material itself. If your attic has blown-in insulation, rabbits, or active pest traffic, expect to check the foil every 3 to 5 years for tears and sagging. Call (903) 437-9164 and we’ll inspect it as part of a free estimate for any replacement work.
Small tears in otherwise intact foil can be repaired with foil tape and re-stapling, and we do this as a low-cost fix when the damage is limited to one or two sections. The problem is that dust-coated or sagging foil across 40% or more of the attic means the reflective surface is already compromised. Repairs on a failed barrier buy you a few years at best. We’ll tell you which one you have and give you the repaired-versus-replaced price honestly.
Most standard single-story San Antonio homes take one full day, including removal of old foil, cleaning the rafter contact points, and full installation. Larger two-story homes or attics with steep pitches may take a second day. We’ll give you a firm schedule when we quote, and we start when we say we’ll start.
Yes. We keep Johns Manville perforated foil in both 26-inch and 50-inch widths in our San Antonio inventory, and we carry Reflectix for homeowners who have existing partial Reflectix coverage and want a matching product. If your attic needs the wider roll and we don’t have enough on the van, we can typically source it same-day or next-day from our local supplier without rescheduling your install. Call us at (903) 437-9164 for a free estimate and we’ll confirm what’s needed for your specific attic before anyone schedules anything.
Contact Thistledown Insulation San Antonio
If your attic is cooking, your upstairs rooms won’t cool, or you just pulled down the ladder and saw sagging foil, call us. We’ll walk the job quietly, measure what’s there, and hand you a written price before any work begins. A live person answers at (903) 437-9164, day or night.
Written by Neil Barron, Owner, Thistledown Insulation San Antonio at Thistledown Insulation San Antonio, serving San Antonio and nearby areas.