Radiant Barrier for Attics

An attic radiant barrier reduces radiant heat exchange across an adjacent air space. In a hot climate, that can reduce the heat reaching attic insulation, ductwork, and air-handling equipment. The result depends on the roof, climate, ventilation, existing insulation, and installation quality.

Where should radiant barrier go in an attic?

For many existing homes, the preferred position is beneath the roof rafters or top chords of the trusses. This places a reflective surface between the hot roof deck and the attic while keeping the material above ducts and equipment. It also leaves the downward-facing surface sheltered from settling dust.

Radiant barrier can also be placed over attic-floor insulation where rafter access is impractical. That method is easier in some attics, but dust on the upward-facing surface can reduce its effectiveness. The material must not block soffit, ridge, or gable ventilation.

Why the air space matters

A reflective surface needs to face an air space to function as a radiant barrier. If both faces are tightly sandwiched between solid materials, heat moves primarily by conduction and the reflective surface cannot provide the same benefit. Ra-flect is reflective on both sides, so there is no front-versus-back orientation to remember.

Choose roll width around the framing

What radiant barrier does not replace

Radiant barrier and conventional insulation address different heat-transfer mechanisms. Radiant barrier does not replace attic-floor insulation, air sealing, duct repair, or ventilation. It is one part of the complete attic system.

Plan the installation safely

• Work during cooler hours and use stable walking boards and adequate lighting.
• Keep the material clear of flues, chimneys, recessed fixtures, and other heat-producing equipment as required.
• Do not cover ventilation openings or create unintended moisture traps.
• Pre-cut manageable lengths before carrying material into a tight attic.

For additional building-science guidance, review the Building America attic radiant barrier guide and the U.S. Department of Energy radiant barrier overview.