A greenhouse having side walls that provide a structural frame and which define an enclosed growing area. The greenhouse also has a roof which extends from the structural frame, and which has multiple roof sections extending inwardly over the growing area. A first roof section covers a first portion of the growing area and terminates in a first remote edge which is spaced inwardly from the structural frame. A second and subsequent roof sections covers the growing area and terminates in a second remote edge which overlaps the first remote edge, thus defining a vertical gap between the adjacent roof sections through which air can circulate. The greenhouse also has a cooling system mounted to a roof section which has nozzles for spraying water vapor into the circulating air, thus cooling the air.