No special use permit shall be issued for a specialized senior housing facility where any residential unit in such facility is less than 320 square feet or where, in the case of double occupancy, any residential unit provides less than 200 square feet per occupant, or where any residential unit is less than 14 feet in width. Additionally, no residential unit in any such facility shall be occupied by more than two persons, regardless of the number of bedrooms in such unit, and no more than 20% of all residential units in such a facility shall have double-occupancy. The square feet of a residential unit with regard to this provision shall be calculated by calculating the square footage of all areas within the demising walls of each individual unit.