Cooling

Depending on the climate, it may sometimes be necessary to cool a greenhouse to provide suitable growing conditions for plants that thrive in cooler climates. Whether it's because the temperature rises too much in the summer or because a cool climate crop is grown in a tropical area, several solutions are available to reduce the temperature inside a greenhouse.

Natural ventilation:

  • It uses the natural movement of both hot and cool air to maintain a temperate climate in the greenhouse by utilizing the chimney effect.
  • It has a very low operating cost with little or no energy input.
  • It is achieved by opening the different ventilation systems provided with the greenhouse: roof or side vents, motorized or manual.
  • It promotes steady temperature control without sudden changes or drafts that could harm the health of plants.
  • It is slower than mechanical ventilation when a rapid change of temperature is needed.
Mechanical ventilation:
  • It expels hot air from the greenhouse with the help of extraction fans, which creates negative pressure. The pressure is then normalized by allowing fresh air through an inlet, thereby effectively cooling the greenhouse.
  • It has an impact on the energy balance of the greenhouse as it powered by electricity.
  • It causes sudden and rapid changes in temperature and creates drafts because of the on / off cycles.
  • Available with variable speeds and with diameters between 12'' and 50''.

Misting:

  • Linked to the irrigation system, this solution cools the greenhouse by spraying a fine mist. This mist, as it evaporates, cools the temperature inside a greenhouse.
  • Particularly effective in areas with hot and dry climates as it requires a low relative humidity level to be truly efficient.
  • Not recommended in temperate climates or for crops susceptible to fungal problems.

Cooling pads

  • This solution requires mechanical ventilation equipment to operate properly.
  • Extraction fans are placed at one end of the greenhouse and the cooling pads are installed at the other end, in front of a fresh air inlet (usually louvers).  When the fans are activated, they create a negative pressure inside the greenhouse, which in turn forces fresh air through the pads.  
  • By moving through the moistened pads, the hot air evaporates the water they contain, cooling it before it penetrates the greenhouse.
  • Useful for cooling large areas effectively.
  • It requires a warm and dry climate to be effective.
  • Good alternative to misting with crops susceptible to fungal diseases.