The protection that the greenhouse roofing provides for the crops prevents harm caused by bad weather conditions outside - excessive insolation, low temperatures, heavy rain, strong winds, etc., but it also limits the renovation of air and slows its movement in the interior. Air is employed in transpiration, respiration and photosynthesis. An appropriate rate of changing the interior air together with an adequate movement can provide optimum levels of temperature, hygrometric deficit and concentration of carbon dioxide uniformly throughout the volume of the greenhouse.
Forced ventilation systems for destratification of the air:
The systems comprise a set of small helical fans distributed over the area of the greenhouse in different arrangements.
The objective of their operation is to generate small air currents that allow mixing and standardizing of the conditions therein.
When the windows are closed, or the greenhouse air-change rate is low or zero, a small air current crossing the crop canopy substantially improves the exchange of gases, avoiding saturation conditions due to excessive humidity in low temperature conditions and improving transpiration under conditions of high temperature.
The forced ventilation systems have, on one hand, a set of helical fans installed in a plane (sides or fronts of the greenhouse), usually working as extractors; on the other hand, working in combination, they have a doorway or window that controls the access of air.
This equipment allows each greenhouse to be provided with the appropriate ventilation rate for each case.
The untreated external air evacuate the heat and transpiration load, thereby avoiding excessive temperature and humidity conditions. Combined with misting systems, or being an integral part of a set of evaporator panels, it offers the best results as regards its capability as a cooling system.