No building shall exceed the height limits as prescribed in Section 25-4. Penthouses or roof structures for the housing of stairways, tanks, ventilating fans, air conditioning equipment or similar equipment required to operate and maintain the building; skylights; spires; cupolas; flagpoles, chimneys; antennas and radio towers; or similar structures may be erected on the building above the height limits prescribed by this chapter, but in no case may the combined height of the structure and facility be more than one hundred twenty-five (125%) percent of the maximum height permitted for the use in the district.