How Radiant Barriers work:
Radiant barriers are an insulation system consisting of a low emittance (normally 0.1" or less) surface bounded by an open air space. The low emittance surface (pure aluminum foil) limits up to 97% of radiant heat transfer. Radiant barriers works exceptionally well in sunny climates where a significant amount of the heat transfer into and out of a home is through radiation. Radiant barriers can used alone, or in conjunction with mass insulation (fiberglass, sprayfoam etc.) to create a hybrid insulation system for enhanced thermal performance.