1.1 ,This practice has been prepared for use by the designer, specifier, builder, and the installer of radiant barrier systems (RBS) for use in commercial/industrial building construction not otherwise restricted from use. The scope is limited to instruction relative to the use and installation of RBS, including a surface(s) normally having an emittance of 0.1 or less, such as metallic foil or metallic foil deposits, mounted on substrates. Some examples that this practice is intended to address include: (1) low-emittance surfaces in vented building envelope cavities intended to retard radiant transfer across the airspace: (2) low-emittance surfaces at interior building surfaces intended to retard radiant transfer to, or from, building inhabitants, and (3) low-emittance surface at interior building surfaces intended to reduce radiant transfer to, or from, radiant heating or cooling systems.