All exterior lighting in business, office, industrial and residential districts, including the lighting of signs, shall be directed away from adjoining streets and residential properties and, in connection with multifamily or nonresidential uses in residence districts, shall be so located and shielded that the light sources are not directly visible from any adjoining property or from the street and that any such illumination does not cause glare observable within an R-20, R-10, R-7.5 or 2R District. In acting on any special use permit application, the Board of Appeals, as a condition of approval, may also restrict hours of lighting and types of fixtures.