In all Residence Districts, the obstructions set forth in Section 23-621 (General permitted obstructions), as well as the following obstructions, shall be permitted to penetrate a maximum height limit or sky exposure plane.

1. Balconies, unenclosed, subject to the provisions of Section 23-13;
2. Dormers having an aggregate width of street walls equal to not more than 50 percent of the width of the street wall of a detached or semi-detached single- or two-family residence;
3. Elevator or stair bulkheads (including shafts; and vestibules not larger than 60 square feet in area providing access to a roof), roof water tanks, energy infrastructure equipment, and accessory mechanical equipment (including enclosures), other than solar or wind energy systems (whether accessory or as part of energy infrastructure equipment), provided that:
   1. such obstructions shall be located not less than 10 feet from the street wall of a building, except that such obstructions need not be set back more than 25 feet from a narrow street line or more than 20 feet from a wide street line. However, such restrictions on location shall not apply to elevator or stair bulkheads (including shafts or vestibules), provided the aggregate width of street walls of such bulkheads within 10 feet of a street wall, facing each street frontage, does not exceed 30 percent of the street wall width of the building facing such frontage;
   2. the aggregate area of such obstructions, including any required screening, does not exceed 50 percent of the lot coverage of the building;
   3. the height of obstructions within an aggregate area equivalent to at least 20 percent of the lot coverage of the building shall not exceed 15 feet above the maximum permitted height; and
   4. the height of obstructions within the remaining lot coverage, not to exceed 30 percent of the building shall not exceed:
      1. in R3-2, R4, and R5 Districts, except R4-1, R4A, R4B and R5A Districts, a height of 25 feet above the maximum permitted height;
      2. in R6 through R10 Districts:
         1. where the maximum permitted height of a building is 120 feet or lower, a height of 35 feet above the maximum permitted height; and
         2. where the maximum permitted height of a building is greater than 120 feet, a height of 55 feet above the maximum permitted height; and
   5. all equipment shall be subject to the applicable provisions of Section 26-60 (SPECIAL SCREENING AND ENCLOSURE PROVISIONS);
4. Wind energy systems, accessory or as part of an energy infrastructure equipment, on portions of buildings with a height of 100 feet or greater, provided:
   1. the highest point of the wind turbine assembly does not exceed 55 feet;
   2. no portion of the wind turbine assembly is closer than 10 feet to any lot line; and
   3. the diameter of the swept area of the rotor does not exceed 15 feet.