Roof Vent

Sidewall Vents
Sidewall ventilation may be installed as roll-up sidewall curtains (Figure 6.2) or as hinged vents (Figure 6.3). Sidewall vents are typically 2 to 3 feet (0.6–0.9m) tall and installed at the ground level. Because natural ventilation relies on wind or pressure differences, sidewall vents should be installed on the length walls of a greenhouse and on walls free from outside obstructions such as vegetation or other buildings. Although some curtain systems open up from the bottom (i.e., roll-up), systems that open down from the top (i.e., drop-down) are preferred.

Ridge Vents
Sidewall vents paired with the roof or ridge ventilation may increase airflow through a greenhouse (Figure 6.4). Ridge ventilation can be installed as a retractable, hinged, rigid-glazed vent or as a framed-poly film-hinged vent. Ridge ventilation can also be installed as a roll-up roof.

Vent Operation
Vents can be opened with a manual crank or with a motorized control. In large greenhouses, motorized control is more efficient and saves labor costs. A thermostat can be connected to the vent system so that it is completely automatic; however, most systems integrate automatic vent operation with a computerized climate control system. Thermostat controls or climate control systems are set at a desired temperature.

Open-Panel Greenhouses
Open-panel greenhouse designs, which allow for natural ventilation, rely on wind pressure and temperature differences to remove heated air and introduce fresh air, often through roof vents and sidewall openings, allowing for maximum control of humidity and ambient temperature (Figure 6.5). The design offers full plant exposure to the natural light entering the greenhouse and is ideal for hardening crops.