One lighted or unlighted sign for each hospital, church, parish house, rectory, school, rest home, convalescent home, and nursing home, library, museum, government building, professional medical office, outpatient care facility, medical laboratory, health spa, community center, institutional use, public recreation building, retail building, automobile sales building, restaurant, bank, or shopping center naming such building, either affixed flat to the building or erected in the yard space, provided such sign does not exceed 20 square feet in area.