Air is a source of gas for cactus and other plants to thrive. It is at night that the cactus metabolizes through its cessinic acid, absorbs carbon dioxide through the stomata in the stem and stores it for photosynthesis during the day. However, at night, the greenhouse may be tightly closed and plants in the greenhouse may require air circulation or ventilation.
Any type of fan will circulate the air. The ventilation system introduces new air and exhausts old air. The greenhouse also uses ventilation as a cooling method. The ventilation fan should exhaust sufficient air to provide an air change per minute at an 8-foot (2.4 m) height. For example, a greenhouse with an area of 20 x 50 feet (6 x 15 meters) requires a rated capacity of to 20 x 50 x 8 = 8000 cubic feet (6 x 15 x 2.4~220 cubic meters) per minute.
Greenhouses can benefit from horizontal airflow fans designed to move large amounts of air quickly. However, horizontal airflow fans are expensive and are generally only recommended for greenhouses above 600 square feet (56 square meters). A typical household fan is enough in a small greenhouse. The air circulation fan usually runs 24 hours a day.
Small greenhouses can use variable speed fans to save energy, while large greenhouses require multi-fan installations. During the winter months, only one-quarter of the normal air exchange is required. Place the fan on the wall and place the air intake blinds on the opposite wall. The air intake blinds should be at least 1.25 times larger than the fan area. The bottom of the fans and shutters should be about 3 feet (1 meter) above the ground so that the air can flow above the plants.
fully automatic temperature control system temperature control interval is about 1 degree Fahrenheit (0.6 degrees Celsius), which is better than the traditional mechanical thermostat . The traditional mechanical temperature control interval is usually 5 degrees Fahrenheit (2.8 degrees Celsius). For example, setting the temperature of a mechanical air conditioner to 80 degrees Fahrenheit (27 degrees Celsius), it will make the fan run until the temperature drops to 75 degrees Fahrenheit (24 degrees Celsius), which will waste electricity and money.
