barrier (shiny side down) should NOT be applied directly over the roof sheathing, because high contact area reduces the efficacy of the metallic surface as low emitter. Vertical battens (aka firring strips) may be applied atop said sheathing; then OSB with radiant barrier may be put atop the battens. The battens allow more air space than construction without battens. If an air space is not present or is too small, heat will conduct from the radiant barrier, into substructure, resulting in unwanted IR shower on lower regions. Wood, be reminded, is a poor insulator and therefore conducts heat from the radiant barrier to lower surfaces of said wood, where it, in turn, sheds heat by emitting IR radiation. According to the US Department of Energy, “Reflective insulation and radiant barrier products must have an air space adjacent to the reflective material to be effective.” The most common application for a radiant barrier is as a facing for attics. For a traditional shingle/tile/iron roof, radiant barriers may be applied beneath the rafters or trusses and under the roof decking. This application method has the radiant barrier sheets draped beneath the trusses of rafters, creating a small air space above with the radiant barrier facing into the entire interior attic space below. Reflective foil laminate is a product commonly used as the radiant barrier sheet. Another method of applying radiant barrier to the roof in new construction is to use a radiant barrier that is pre-laminated to OSB panels or roof sheathing. Manufacturers of this installation method often tout the savings in labor costs in using a product that serves as roof decking and radiant barrier in one. To apply radiant barrier in an existing attic, a radiant barrier may be stapled to the underside of the roof rafters. This method offers the same benefits as the draped method in that dual air spaces are provided. However, it is essential that the vents be allowed to remain open to prevent moisture from being trapped in the attic. In general, it is preferred to have the radiant barrier applied SHINY SIDE DOWN to the underside of the roof with an air space facing down; thus dust won't defeat it, as would be the case of a SHINY SIDE UP barrier. The final method of installing a radiant barrier in an attic is to lay it over the top of the insulation on the