Metal Building Insulation: Reflective Liners & Radiant Barrier
Our own steel building in Rhome, Texas, lined with IIP double bubble.
Application · Metal buildings, shops & warehouses · Ships from Rhome, Texas
Metal Building Insulation: Reflective Liners & Radiant Barrier
Steel roof and wall panels soak up the sun and radiate that heat straight into the building. A reflective liner turns radiant heat back at the panel, and with taped seams it acts as a vapor retarder that helps control condensation on the steel. IIP makes white-faced and foil-faced liners in widths from 4 to 8 ft (1.22 to 2.44 m), so you can match your purlin spacing or cover long runs with few seams.
R-values for reflective products depend on the enclosed air space and are shown with the conditions stated, as the FTC R-value Rule requires.
Why it works
Reflects radiant heat
Metallized faces turn back heat radiating from hot roof panels. The reflective face needs an air space next to it; a 3/4 in (19 mm) gap is the basis for the R-values we publish.
Helps control condensation
Bubble liners and woven barriers are low-perm films. Installed with overlapped, taped seams, they slow warm moist air reaching cold steel, the usual cause of dripping roofs.
Finished interior
The white face of our foil/white products gives a bright, clean surface where the liner stays visible, so no extra ceiling is needed.
Recommended IIP products
Which liner for which part of the building
| Use | Product | Why |
|---|---|---|
| Roof, over or under purlins | Double Bubble Foil/White or Foil/Foil | White face down for a finished ceiling |
| Walls, on the girts | Double Bubble Foil/White | Wide rolls mean fewer vertical seams |
| Thickest single-layer walls and roofs | Superbubble 1 in | 1 in (25 mm); system R-values under independent test |
| Budget or light-duty buildings | Single Bubble Foil/White | Lighter, lower cost per roll |
| Seams and edges | IIP seam tapes | White tape on white faces, aluminum on foil |
How to install
- Measure the roof and wall areas in square feet and choose a roll width that matches your purlin or girt spacing: 4, 6 or 8 ft (1.22, 1.83 or 2.44 m) by 125 ft (38.1 m).
- New buildings: run the liner across the purlins and girts before the panels go on. Existing buildings: fix it to the inside of the framing.
- Keep an air space of at least 3/4 in (19 mm) on the reflective side, using the framing, spacers or furring.
- Overlap sheets by at least 2 in (51 mm) and seal every seam with IIP tape so the liner works as a continuous vapor retarder.
- Seal edges and penetrations, then install the panels or interior trim.
General guidance. Follow local building codes and the product data sheet for your job.
Questions we get asked
What R-value does a metal building liner give?
Double Bubble Foil/White is rated at R-17.2 (RSI 3.03) as a system with heat flowing down, by the ASTM STP1116 method. Double Bubble Foil/Foil gives R-7.95 heat flow down and R-5.42 horizontal with at least a 3/4 in (19 mm) enclosed air space.
Will it stop my roof from dripping?
A reflective liner installed with overlapped, taped seams acts as a vapor retarder, which is the main defense against condensation on the steel. Ventilation and sealing gaps at the eaves and ridge still matter.
Can I add it to an existing building?
Yes. Fix the liner to the inside of the purlins and girts, keep the air space on the reflective side and tape all seams.
What sizes do the rolls come in?
4 ft × 125 ft (500 sq ft), 6 ft × 125 ft (750 sq ft) and 8 ft × 125 ft (1,000 sq ft). Custom widths and lengths are available on request.
Is it fire rated?
Yes. Double Bubble Foil/White tested Class A / Class 1 on both faces and the taped joint under ASTM E84-24 (R&D Services, 2025). Our other bubble and barrier products are Class A / Class 1 under ASTM E84.
How is it priced and shipped?
By the roll with pallet pricing, shipped LTL freight from Rhome, Texas to the US and Canada. Send your square footage and ZIP for a delivered quote.
Pricing a metal building?
Send the roof and wall square footage and your ship-to ZIP. We quote rolls and LTL freight the same business day.