louver
In American architecture, a louver is one of a series of overlapping boards or narrow panes of glass used to fill a window opening, keeping out rain while allowing ventilation. 2. A lantern or turret on the roof of a medieval building having slatted apertures for the escape of smoke and admission of air. Photo from New York City, New York, 2019. (Howe, 2002)
louvre, louvers, louvres, ventilator