Height limitations. District height limitations shall not apply to church spires, cupolas and domes, monuments, water towers, chimneys, smokestacks, farm structures, silos, flagpoles, utility poles, radio and television antennas or aerials, utility towers and parapet walls extending not more than four feet above the limiting height of the building. Such structures shall have yards equal to the vertical height thereof. The Board of Appeals, after review by the Planning Board, may waive the height limitations of this chapter as they pertain to elevator apartments and to commercial and manufacturing buildings. In such cases, the Board of Appeals shall determine that such a departure is in the best interests of the municipality, that it will be compatible with and not cause substantial injury to the value of other adjoining property and that adequate off-street parking, loading and fire protection will be provided.