Signs of schools, colleges, universities, places of worship, hospitals, public sanitariums, charitable religious, and civic/institutions when located on the premises thereof, with a sign area of no more than 40 square feet if single-faced, nor more than 80 square feet if double-faced, used exclusively for noncommercial purposes, and the top of which is not more than eight feet above ground. No more than one such sign shall be placed on a property in single and separate ownership, unless such property fronts upon more than one street, in which event one such sign may be placed on each frontage.