The provisions of this Section shall not apply to any zoning lot subdivided to under four acres after January 1, 1972, nor to any large-scale residential development for which authorization has been granted by the City Planning Commission prior to July 31, 1972.

In R3-2 or R4 Districts, or in Commercial Districts in which residential buildings are governed by the bulk regulations of such Residence Districts, for any large-scale residential development which complies with the requirements of Section 78-34 (Special Permit Provisions for Certain Large-scale Developments), the permitted residential floor area ratio, required open space ratio and density regulations for the large-scale residential development as a whole may be modified as set forth in this Section. At least 25 percent of the total required open space is to be provided in common areas meeting the requirements of Section 78-52 (Common Open Space). No portion of such common open space is to be used for driveways or off-street parking. The findings required in paragraph (e) of Section 78-313 (Findings) are to be satisfied.

The maximum number of dwelling units shall equal the total residential floor area permitted divided by the applicable factor in Section 23-20 (DENSITY REGULATIONS).

In R5 Districts, or in Commercial Districts in which residential buildings are governed by the bulk regulations of such Residence Districts, at least 25 percent of the total required open space is to be provided in common areas that meet the requirements of Section 78-52. No portion of such common open space is to be used for driveways or off-street parking. All findings required in paragraph (c) of Section 78-313 are to be satisfied.