Ventilation

Ventilation is essential for healthy crops.  When properly done, ventilation will help control temperature, humidity and contribute to the even distribution of CO2 (when needed). There are many solutions available to ensure your crops benefit from optimal ventilation:

Natural ventilation:
Harnois greenhouses were designed to maximize the effectiveness of natural ventilation. In the large majority of projects, it is the only type of ventilation necessary.

  • When it is manual, this ventilation has a very low operating cost without energy input
  • Is accomplished by opening the different ventilation systems provided in the greenhouse: at the roof, and/or on sides and can be manual or motorized
  • Uses the natural movement of hot and cool air to maintain a temperate climate in a greenhouse by a chimney effect
  • Promotes steady temperature control without sudden changes or drafts that could harm the health of plants

Air Circulators:

Air circulators, commonly called Horizontal Air Flow fans or HAF fans, are devices essential to maintain a climate suitable for growing plants in greenhouses. Their primary function is to gently mix the air inside the greenhouse to promote a uniform temperature throughout the area.

These fans are inexpensive and promote consistent growth and water needs throughout the covered areas, which greatly facilitates crop management and optimize performance. Furthermore, by drying the foliage, they can contribute to preventing fungal diseases.

Mechanical ventilation:

Although mechanical ventilation is less popular today than 30 years ago, it is the only effective alternative for closed circuit greenhouses.  Mechanical ventilation:

  • Has an impact on the energy consumption of the greenhouse when powered by electricity
  • Expels hot, moist air from the greenhouse which creates a negative pressure. The pressure is then normalized by drawing fresh air into the greenhouse through an inlet, thereby effectively venting the greenhouse
  • Can cause sudden and rapid changes in temperature and can create drafts because of the on/off cycles
  • Available with variable speeds and with diameters between 12'' and 50''
  • Is required for cooling systems using evaporating pads ("cooling pads")
  • Is the sole option for greenhouses that require high-containment level for biohazards.