Size, average high temperatures, and cost will be the biggest factors affecting your choice of systems. In general, however, many greenhouses use a combination of these systems, depending on the time of the year and high temperatures encountered. Most cooling systems are developed to cool in stages. When temperatures first start to rise, natural ventilation could be used to cool the greenhouse. Opening doors or side and ceiling vents will allow natural air flow to reduce the temperature inside the greenhouse.
Some greenhouses have inflatable walls on the side.
The walls are deflated and lowered to allow natural air currents to ventilate the greenhouse. Shade cloth may be suspended over the plants or applied on the greenhouse itself. Next, as temperatures continue to rise, a set of fans may turn on to further increase air flow and cool the interior. A final stage may be fogging or cooling pads. Cooling the air and moving it around will help to cool the plants.