; or (B) the Secretary specifically provides pursuant to subsection (c) for the applicability of such standard. (b) Enhanced energy efficiency standards for purposes of providing additional credit under certain federally assisted housing programs (1) Purpose and effect (A) Purpose The purpose of this subsection is to establish energy efficiency and conservation standards and green building standards that— (i) provide for greater energy efficiency and conservation in structures than is required for compliance with the energy efficiency standards under subsection (a) and then in effect; (ii) provide for green and sustainable building standards not required by such standards