The Atrium Greenhouse Vent System is a unique ridge vent that opens outward and upward from near the top of the ridge. It offers natural ventilation in a system that brings the outdoor environment inside the greenhouse. Opening vertically to 85 degrees, each house can be treated as a zone, allowing you total flexibility in cooling and venting. There are fewer obstructions than other open-roof-style structures, leading to higher light levels. Nexus Corporation. (800) 2-BUY-NEX.