Types of Commercial Greenhouse Ventilation Systems Using Mechanical Cooling

Mechanical greenhouse ventilation systems almost always involve some type of fan-assisted ventilation to provide consistent airflow and air exchange. Typically, fans work in conjunction with intake and exhaust vents to move air across the greenhouse.

• Fan and pad cooling creates an evaporative cooling effect when exhaust fans and vents draw warm air from outside the greenhouse through a wet wall that cools the air as it passes through it to lower temperatures inside the greenhouse.
• Fog (Mist) systems use a high-pressure pump to atomize water and spray a fine mist through nozzles placed throughout the greenhouse to increase humidity and cool the air.
• Swamp coolers, also known as single-unit evaporative cooling systems, operate similarly to fan-and-pad cooling but they are self-contained and typically used for smaller, freestanding greenhouses.

More on Fan-and-Pad Cooling 

Fan and pad cooling works most effectively when the outside air has low humidity because evaporative cooling works based on differences between outdoor and indoor conditions.

Here’s a quick rundown on how fan and pad systems use evaporation to cool the greenhouse:

• Exhaust fans and open vents on one side of a greenhouse create a vacuum effect that draws warm outside air into the greenhouse and through a wet wall located on the opposite end.
• As the warm air passes through the wet wall, the air begins to cool as it loses heat and gains moisture.
• The cooled air leaving the wet wall spreads out across the greenhouse, cooling the temperature and raising the humidity level as it goes.

In more humid conditions, you can still use fan and pad cooling, but it is essential to know that the cooling effectiveness might not match that of drier conditions.

You can also reduce the efficiency of fan and pad systems if you don’t properly size them for your greenhouse, and if you don’t keep them in good condition with regular maintenance.