Rockwool Radiant Barrier Installation Nationwide

Rockwool Radiant Barrier Installation: The Leander Owner’s Guide

Rockwool radiant barrier installation in Leander typically runs $2,400-$4,800 for a 2,000-square-foot attic, depending on whether we’re layering over existing insulation or stripping back to the deck first. We stock Rockwool Comfortboard 80 and Rockwool Comfortboard 110 rigid board for radiant barrier assemblies, and most Leander jobs are scheduled within 48 hours. Homeowners usually figure out something’s wrong when their upstairs bedrooms won’t cool below 78°F by 10 p.m. in July, or when their AC compressor runs nonstop and the electric bill spikes $80-$120 in a single month.

Call (737) 252-7159

Which Rockwool Models This Applies To

Rockwool doesn’t manufacture a standalone radiant barrier product. What we install is a radiant barrier assembly using Rockwool rigid board, typically Comfortboard 80 or Comfortboard 110, paired with a reflective facing or standalone foil layer. Comfortboard 80 runs 8 pounds per cubic foot density, R-4.2 per inch. Comfortboard 110 runs 11 pounds per cubic foot, R-4.3 per inch. The 110 is what we spec for Leander attics with cathedral ceilings or anywhere the assembly takes foot traffic during service.

Here’s the compatibility gotcha: Rockwool Comfortboard has a black mat face on one side and a plain face on the other. The reflective facing must be factory-laminated or field-applied to the correct side. We’ve found previous installs in Leander’s Crystal Falls neighborhood where the foil went on the black mat side, which traps moisture and delaminates within two seasons. The part number you want is on the board edge stamp, format “CB 80 2x48x96” or similar. If that stamp is painted over or sun-faded, measure thickness and weigh a 2×2 sample, a bathroom scale works fine. Comfortboard 80 at 2 inches thick weighs just under 11 pounds for a 4×8 sheet.

OEM Rockwool board with factory-applied foil facing costs 15-20% more than field-laminating generic foil to bare Comfortboard. We stock both. For attic floors in Leander’s climate, we typically recommend the aftermarket assembly, it performs identically in blower-door-verified jobs. For wall assemblies or anywhere the foil faces a vented cavity, factory lamination is worth the premium, the adhesive bond survives humidity cycling better.

Signs Your Rockwool Radiant Barrier Installation Is Failing

• Upstairs rooms stay hot past midnight. The radiant barrier’s reflective surface has oxidized, dirtied, or delaminated, dropping emissivity above 0.30. Once that happens, the assembly quits rejecting solar gain and your attic becomes a radiator pointed at your ceiling.
• AC runs 18+ hours daily in July but never reaches setpoint. The Rockwool board itself is likely intact, but the radiant barrier layer has failed. The insulation still slows conduction, but radiant heat transfer, which dominates attic heat gain in Leander’s 140°F peak attic temps, is now unchecked.
• Foil facing is visible and has turned dull, chalky, or spotted with corrosion. This is direct evidence of emissivity failure. Bright foil should read below 0.05 emissivity. Chalky aluminum reads closer to 0.20, which is barely better than bare roof decking.
• Moisture staining on the attic-side of drywall, especially near bathrooms or kitchens. The vapor profile is wrong, usually because a previous contractor stapled foil directly over old fiberglass without air-sealing first. Warm moist air hits the cool foil, condenses, and the Rockwool wicks it inward. We’ve seen this exact failure pattern in Leander homes built 2015-2019.
• Board edges are crumbling or have pulled away from fasteners. Comfortboard is mineral wool, it doesn’t mold, but it will sag if the fastener pattern was wrong or if someone used standard roofing nails instead of cap nails with 1-inch washers. In Leander’s freeze-thaw cycle, a 20-degree attic swing from night to day accelerates the fatigue.

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Replacement Cost & What’s Included

What drives the range: attic square footage, current insulation condition, and how many can lights, HVAC penetrations, and top plates need sealing before the new assembly goes in. We don’t price by the square foot alone. A 1,800-square-foot attic with twelve can lights and a furnace platform takes longer to seal correctly than a 2,400-square-foot attic with two penetrations. Every job gets a written price before work starts, Haven Standard Clause 1. The 365-Day Done Right Promise covers labor and materials. We source Rockwool through standard distribution, no proprietary lock-in.

DIY or Call Us?

What you can safely check: verify the board edge stamp if visible, look for the dull or chalky foil we described, and note any moisture staining pattern. A phone flashlight and a camera are enough to document what you’ve got.

Where DIY goes wrong: radiant barrier installation in a vented attic is not technically complex, but the sequencing matters more than the stapling. If you lay new foil over unsealed top plates, you’re building a condensation trap. If you compress Rockwool Comfortboard against recessed can housings, you create a hot spot that degrades the board and the fixture. If you don’t verify with a blower-door test, you don’t know whether the air sealing worked. We’ve pulled back DIY installs in Leander where the homeowner did competent work but missed four top plate gaps that collectively leaked 800 CFM50, more than the bathroom fan they were trying to compensate for.

We carry Rockwool Comfortboard 80 and 110, foil facing, and cap fasteners on the truck. Call (737) 252-7159 for a written price before any work starts. Estimates are free, and we publish a Free Second Opinion on any written estimate you bring us.

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