Ventilation is a crucial tool for growers to create a good growing climate in their greenhouses. Opening from the ridge, the ventilation vents are positioned at the highest place of the Dutch Venlo greenhouse, making it the best position to discharge hot air from the greenhouse. There are several options regarding the ventilation window capacity of a Venlo greenhouse, choices can be made between 1 pane-, 2 pane, 3 pane- and 4 pane-ventialtion. Another option is continuous ridge ventilation, this provides the most ventilation capacity by opening up all glass panes at the ridge. The depth of the windows also largely influence the ventilation capacity of the greenhouse.
Greenhouse Ventilation Mechanism
Ventilation Mechanism
Push-Pull Mechanism
There are several options for ventilation mechanism in greenhouses, from a swinging system to a gear system. In modern Dutch greenhouses, the push-pull mechanism the way to go. At the ends however, to create extra ventilation capacity, a separate gear system can be installed.
When it comes to Dutch Venlo greenhouses, the push-pull mechanism is the mechanism of choice. The push-pull-tube slides above the upperside of the truss. The push-pull-tube is connected to the lower aluminium profile of the ventilation-window section by means of push-rods. The amount of push-rods that are required is dependent of the ventilation window size and the wind speeds that are taken into account. Drive motors allow the push-pull-tube to move back and forward and with that, regulating the opening of the vents.
Do you want to know more about ventilation mechanisms?
Do you want to know more about ventilation mechanisms?
Venturi Effect
The ventilation windows have a so called windward and leeward side, opening the windows is key to have a Venturi effect that the air is pulled out of the greenhouse, this is usually warmer and moist air, ensuring a proper air humidity level in the greenhouse.
Ventilating the greenhouse is essential in the morning when the plants start to evaporate a lot of moist is released from the greenhouse. With the height of the greenhouse and sufficient buffer space the ventilation windows are opened as little as possible. This allows for optimal saving of energy and providing a calm climate within the greenhouse. Utilising the Venturi effect can keep the opening minimal, whilst benefiting from the opened ventilation window.
Semi-closed greenhouses minimize the use of ventilation windows and recycle the air inside the greenhouse, treating the inside air by de-humidifying and cooling or heating the air. Minimizing the air exchange with the outside air to maximize on carbon dioxide levels and minimize on energy consumption.
FAQ
The recommended type of ventilation mechanism for Dutch Venlo greenhouses is the push-pull mechanism. This is because of its reliability, ease of installation and cost efficiency.
The optimal amount of window panes that can open is determined by the ventilation capacity required. This typically is determined by the climate, the crop and growers' strategy.
The opening of ventilation windows is one of the first things to be automated in greenhouses. In the early years using the properties of expanding liquids, nowadays the climate computer powers the drive motor of the push-pull ventilation mechanism.
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