In Commercial Districts that are mapped within, or have a residential equivalent of an R6 through R10 District without a letter suffix, for sky exposure plane buildings, the height and setback regulations set forth in Section 23-736 shall be modified as follows:

1. the sky exposure plane may be measured from a point above the street line instead of the front yard line. The maximum height of a front wall within the initial setback distance shall be the maximum height for front walls permitted in the applicable district for a residential, commercial, or community facility building, whichever permits the greatest maximum height;
2. in C1-8, C1-9, C2-7 or C2-8 Districts or in C1 or C2 Districts mapped within R9 or R10 Districts, the provisions of paragraph (b) of Section 23-736 (Special height and setback regulations for sky exposure plane buildings) shall not apply to any development or enlargement with more than 25 percent of its total floor area occupied by residential use;
3. in Commercial Districts mapped within, or with a residential equivalent of, an R9 or R10 District, towers may penetrate a sky exposure plane pursuant to Section 35-715 (Tower regulations).
4. Notwithstanding the foregoing, in C1 or C2 Districts mapped within, or with a residential equivalent of an R7-2, R8, R9 or R10 Districts, the provisions of Section 23-738 (Height limitations for narrow buildings or enlargements) shall apply to buildings with street walls less than 45 feet in width. However, the street wall location provisions of paragraph (e)(4) of such Section need not apply.