of the building, (bb) that the modifications are expected to reduce such building’s site energy usage intensity by 50 percent or more in comparison to the baseline energy usage intensity of such building, and (cc) as of any date following installation of building modifications, that such modifications have been installed. (II) Baseline energy usage intensity The term baseline energy usage intensity means the site energy usage intensity as of any date during the 24-month period immediately preceding the building modifications described in the qualified retrofit plan. (III) Site energy usage intensity The site energy usage intensity shall be determined for the entire building in accordance with such regulations or other guidance as the Secretary may provide and measured in British thermal units per square foot per year. (IV) Qualified professional The term qualified professional means an individual who is a licensed architect or a licensed engineer or meets such other requirements as the Secretary of Energy may provide. . (b) Increase for buildings in high-Cost areas Paragraph (2) of section 42(e) of the Internal Revenue Code of 1986, as amended by subsection (a), is further amended by adding at the end the following new subparagraph: (D) Special rule for buildings in high-cost areas which achieve enhanced energy performance In the case of an existing building to which both subparagraph (C) and subsection (d)(5)(B) apply (but for this subparagraph)— (i) subsection (d)(5)(B)(i)(II) shall not apply, and (ii) the rehabilitation expenditures taken into account under subparagraph (A) shall be 160 percent of such expenditures determined without regard to this subparagraph. . (c) Effective date (1) In general Except as provided in paragraph (2), the amendments made by this section shall apply to buildings with respect to which housing credit dollar amounts are allocated after December 31, 2023. (2) Bond-financed projects In the case of any building some portion of which, or of the land on which the building is located,