The greenhouse ventilation system plays a pivotal role in plant health and crop production. Many novice horticulturalists do not attribute slow growth, poor yields, or problems with pathogens to an inadequate greenhouse ventilation system. Most gardeners understand the importance of ventilation systems for temperature control but benefits derived from ventilation systems are multifaceted. Not only are ventilation systems vital to maintaining environmental conditions but they also directly influence a plant’s ability to perform photosynthesis, uptake essential elements, and complete reproductive cycles (pollination). Greenhouse ventilation systems serve four imperative functions: temperature control, humidity control, CO2/oxygen replacement, and air circulation.