The ventilationjet system as a step towards controlled ventilation and adapted properties of insulation screens in greenhouses

Moisture control in a greenhouse based on the creation of screen gaps has many disadvantages. This study describes a new approach where screen gaps are avoided by installing a Ventilationjet system. A speed controlled fan creates an airflow through a small opening in the fully closed screens. A second fan under the screen mixes the cold, dry air with greenhouse air. This system is controlled based on the difference in absolute humidity of the air under and above the screen. This difference, multiplied by the volume of air that is exchanged equals the amount of transpiration produced by the plants. This system was tested in multiple crops including gerbera and roses. This resulted in a 16-23% lower gas consumption in a situation where the screen system was not changed. The reduction was a result of more controlled ventilation and the reduction of horizontal and vertical temperature differences within the greenhouse. Based on these positive results, the development of new screen systems that can be combined with the Ventilationjet system has started. A first test with a cucumber crop resulted in a 63% reduction of energy consumption compared to a standard greenhouse with a single energy screen.