This open-roof structure is designed to use natural ventilation and allows for maximum control of humidity and ambient temperature. The design offers full plant exposure to the natural light entering the greenhouse and is ideal for hardening crops. When the roof is closed, it offers full plant protection and environmental control. The open roof is available in glass, polycarbonate and plastic glazing options and in standard roof spans of 21, 261/4, 311/5 and 42 feet with bay increments of either 10 or 13 feet. Attko Greenhouse, Inc. (770) 222-0410.