Ventilation in greenhouses
Shimon Valensi – Sales Manager, Israel
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Ventilation in greenhouses is essential and it has decisive affects on crop results.


Increases in temperature and humidity levels damage the yield and affect the quality of the crops.  In many cases, higher temperatures and increased humidity are also a burden on greenhouse workers, which indirectly leads to a decline in output and greenhouse profitability.


Ventilation, either on the walls of the greenhouse or along the structure's rooftop, serves as natural ventilation and hot, internal air is expelled through these air vents. 


Due to low levels of internal air pressure and the effect of external winds, cold air is forced into the greenhouse.


Air vents can be controlled either manually or automatically.


Natural ventilation in greenhouses is effective only to a certain length of the structure.  What measures can be taken in greenhouses that extend over an extremely large area?


This is particularly true when growing tomatoes and cucumbers.  The height of the trellised vegetables disrupts the flow of air within the greenhouse.


A number of solutions have been developed to deal with the situation:


The First Solution:  Air Vents along the Rooftop – "The Natural Solution"


One of the solutions currently available on the market is the installation of air vents along the greenhouse's rooftop.  These vents enable the heat and humidity that have accumulated inside the greenhouse to be expelled naturally.  The advantage of this solution is based on the fact that heat rises and the opening of the roof windows enables the heat to be expelled from the structure without any kind of intervention.


The Advantages of Natural Ventilation:

  • Lower installation and maintenance costs
  • No need for electricity
  • Allows for longer gutter front lengths along the greenhouse

The Disadvantages of Natural Ventilation:

  • Low to almost no ability to control and determine internal climate conditions
  • High dependency on external climate conditions

It is important to remember that when choosing the natural ventilation solution, there are technological means for assisting and increasing the internal air flow, such as: 24" air circulators, or as an alternative, circulators combined with a thermal screen.  The addition of these systems is likely to lead to better results.  Clearly, results are also influenced by external weather conditions and the geographic location of the crops.


All of Azrom's models are designed for using the Natural Ventilation Solution.


The Second Solution:  Active Ventilation


This solution requires the installation of a ventilation system within the greenhouse.  The system enables the grower to achieve ideal internal climate conditions while addressing the type of crop, external climate conditions and the size of the structure.


While taking these three factors into consideration, the following systems are required for best results:  fans, air circulators, a humid pad, screens and additional equipment suited specifically to the needs of the grower and the particular crop.


Not only does this solution enable proper ventilation of the greenhouse, it also creates optimal conditions for producing a larger and higher quality yield.


Advantages of Active Ventilation:

  • Full command and control over internal climate conditions
  • Better annual results without dependency on external conditions

Disadvantages of Active Ventilation:

  • Higher costs in comparison to Natural Ventilation
  • Dependency on the supply of electricity
  • Shorter gutter front lengths (a maximum of 36 meters long)

Azrom is currently one of the world's leading companies for the production of greenhouses.


Every project, anywhere in the world, receives the proper, individual consideration, combining: local characteristics, design and planning, agronomic consultation, examination of growing conditions, construction and the planning of supplementary units and systems, including electricity, water, heating, trellising, climate control and fertilization.  Only an overall, comprehensive solution, be it simple or complex, is the perfect response.


The company's quality control policy focuses on the supply of qualitative products for long term client use under difficult and challenging field conditions.


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