N.Y.C. Admin. Code § 27-306: § 27-306 Measurement.

In applying the provisions of this code governing height limits, the following appurtenant structures shall not be included in the height of the building unless the aggregate area of all such structures, exclusive of any solar thermal and solar electric (photovoltaic) collectors and/or panels and their supporting equipment, exceeds thirty-three and one-third percent of the area of the roof of the building upon which they are erected:

(a) Roof tanks and their supports.

(b) Ventilating, air conditioning, combined heat and power systems, and similar building service equipment.

(c) Roof structures, greenhouses, bulkheads, and penthouses.

(d) Chimneys.

(e) Parapet walls four feet or less in height.