The provisions of Article I, Chapter 5 shall apply to the conversion of non-residential floor area to residences, except where such regulations are modified by the provisions of this Chapter. Where the regulations in effect prior to the establishment of this Chapter were utilized to provide floor area for joint living-work quarters for artists in a manner not otherwise permitted by Article I, Chapter 5, such provisions may continue to apply in order to convert such floor area to residences, provided that light and air provisions of Section 15-23, and conversion provisions of Section 143-12 are met.