Is radiant barrier worth it?

In hot climates (South, Southwest) it can reduce cooling costs 5-10%. In cold climates the benefit is minimal. It complements but does not replace insulation.

Does radiant barrier need an air gap?

Yes. Without at least a 3/4-inch air gap on the reflective side, it conducts heat like any other material and provides no benefit.

Will dust ruin radiant barrier?

Dust on the reflective surface reduces effectiveness over time. Installing on rafters (foil down) minimizes dust accumulation compared to attic floor installation.

Insulation

Radiant

$0.15-$0.50 per sq ft

Radiant Barrier: Reflective Attic Heat Reduction (2026)

Prepared by Lumberama's Building Materials Team

|Last updated August 19, 2026|Sources & methodology

Radiant barrier is a highly reflective material, typically aluminum foil laminated to a substrate, installed in attics to reflect radiant heat away from the living space. It does not have an R-value but significantly reduces cooling costs in hot climates by reflecting up to 97% of radiant heat from the roof.

Key Features

Reflects 95-97% of radiant heat; Reduces attic temperature 20-30F; No R-value but reduces heat gain; Staple or drape installation; Most effective in hot climates

Specifications

Emissivity: 0.03-0.05. Reflectivity: 95-97%. Material: aluminum foil on kraft

OSB

or bubble substrate. Perforated options for moisture vapor passage.

Applications

Attic rafters; Attic floor over insulation; Metal building interiors; Under roof deck; Garage ceilings in hot climates

Installation Overview

Staple foil-side down to underside of rafters with 1-inch air gap. Alternatively, drape over attic floor insulation foil-side up. Must maintain air gap on the reflective side to function. Use perforated products in humid climates.

Pros & Cons

Pros

✓ Significant cooling cost reduction; Low material cost; Easy DIY installation; Does not degrade over time; Complements other insulation

Cons

✗ No benefit for heating; Dust accumulation reduces effectiveness; Requires air gap to work; Minimal benefit in cold climates; Not a substitute for insulation

Top Brands

Reach Barrier

EcoFoil

Reflectix

AtticFoil

Code Requirements

No specific code requirement but recognized by IECC as a qualifying energy measure. Must not contact electrical wiring. Perforated versions required in humid climates to allow moisture passage.

Buying Tips

Only cost-effective in hot climates. Perforated products are safer in humid regions. Rafter installation is more effective than floor installation. Can be combined with standard insulation for maximum performance.