The height limitations of this chapter shall not apply to:
A.
Roof projections. Bell towers, steeples, rooftop bulkheads, water towers, fire towers, hose towers, cooling towers, or air-conditioning or heating equipment, provided that such features shall not occupy, in the aggregate, more than 10% of the area of the roof of a building and are set back from the edge of the roof at least one foot for each one foot by which such features exceed the maximum height otherwise specified for the district in which they are located. All mechanical equipment located on the tops of buildings shall be visually screened, subject to Planning Board approval.
B.
Wall extensions. Parapet walls or cornices which do not exceed the maximum height requirement for the district in which they are located by more than four feet.
C.
Solar energy systems. Solar energy systems, provided that such systems shall be erected only to the height necessary to accomplish the purposes they are intended to serve.