The measurement shall be made from the mean finished grade of the lot immediately adjacent to the building foundation.

Height limits in this chapter shall not apply to transmission or aerial towers, masts, flagpoles or chimneys, provided that the horizontal area of such parts does not exceed one and zero-tenths percent of the ground area covered by the main building, nor shall the limits apply to parapet walls not over four (4) feet high for buildings located in nonresidential zones, and further provided that height limits shall not apply to roof-mounted heating, air conditioning or other mechanical equipment, except that such equipment shall not be visible while standing at ground level and shall be screened by a wall, cover, parapet, fencing or by other means equal to the height of the equipment to be screened and such screening shall be in keeping with the architectural motif of the building.