Greenhouse cooling systems are used to control excessive heat during warm periods and help maintain a more stable production environment. Depending on regional climate, greenhouse structure and crop requirements, cooling strategies may combine ventilation, fan-and-pad evaporative cooling, fogging, shading, airflow management and automated climate control.
Why Do Commercial Greenhouses Need Cooling?
Solar radiation can cause greenhouse temperatures to rise rapidly, especially during warm and clear weather.
Ventilation is normally one of the first methods used to remove accumulated heat, but outside air temperature can limit how much cooling can be achieved through ventilation alone.
Where additional cooling is required, evaporative cooling, fogging or other climate-control strategies can be integrated with the greenhouse ventilation system .
How Does Greenhouse Cooling Work?
Greenhouse cooling usually combines several systems rather than depending on one piece of equipment.
Shading and greenhouse design can reduce part of the solar heat load.
Warm internal air is exchanged with outside air where conditions allow.
Evaporative systems can reduce incoming-air temperature under suitable conditions.
Sensors and automation coordinate cooling equipment and climate targets.
Which Greenhouse Cooling Systems Are Used?
Natural Ventilation
Roof and side openings use natural air movement to remove excess greenhouse heat.
Fan-and-Pad Cooling
Exhaust fans pull outside air through wetted cooling pads, reducing air temperature through evaporation.
Fogging Systems
Fine water droplets are introduced into greenhouse air to provide evaporative cooling under suitable conditions.
Shading
Shading systems reduce incoming solar radiation and can lower the cooling load on other systems.
What Is Fan-and-Pad Greenhouse Cooling?
A fan-and-pad cooling system typically places evaporative cooling pads on one side of the greenhouse and exhaust fans on the opposite side.
Water is distributed across the pads. As the exhaust fans operate, outside air is drawn through the wet pad material. Part of the water evaporates and absorbs heat from the incoming air.
The cooled air then moves through the greenhouse toward the exhaust fans.
System performance depends on pad condition, water distribution, fan capacity, greenhouse geometry, airflow resistance and outdoor temperature and humidity conditions.
What Equipment Is Used in a Fan-and-Pad System?
Cooling Pads
Provide a large wetted surface where incoming air interacts with circulating water.
Exhaust Fans
Create the airflow required to draw outside air through the cooling pads and across the greenhouse.
Water Circulation
Pumps, distribution pipes, gutters and tanks continuously circulate water across the cooling pad.
Automation
Sensors and controllers operate fans and pumps according to greenhouse climate conditions.
Fan-and-pad cooling should be designed as an airflow system, not simply as a combination of a wet wall and several fans. Pad area, fan capacity, greenhouse length, pressure losses and control strategy all affect performance.
How Does Outdoor Humidity Affect Evaporative Cooling?
Evaporative cooling relies on water evaporating into the air. For this reason, outside-air humidity has a major effect on cooling potential.
Dry outside air can generally absorb more moisture and therefore provides greater evaporative cooling potential.
When outside humidity is already high, less additional water can evaporate into the air, which reduces the temperature reduction that an evaporative system can provide.
Local summer climate conditions should therefore be evaluated before selecting and sizing a greenhouse evaporative cooling system.
What Is a Greenhouse Fogging System?
Greenhouse fogging systems create very fine water droplets inside the production environment.
When these droplets evaporate before reaching plants or surfaces, they absorb heat from the surrounding air and contribute to cooling.
Fogging performance depends on droplet size, water quality, greenhouse airflow, humidity and control strategy.
The system should be designed to provide controlled evaporation rather than simply wetting the greenhouse environment.
Fan-and-Pad Cooling vs Fogging
| Criteria | Fan-and-Pad | Fogging |
|---|---|---|
| Cooling method | Outside air passes through wetted cooling pads | Fine water droplets evaporate within greenhouse air |
| Air movement | Requires airflow from pads toward exhaust fans | Works with internal greenhouse airflow and ventilation strategy |
| Water system | Pad circulation system with pumps and water distribution | High-quality water and suitable fogging equipment are important |
| Climate effect | Creates a temperature gradient as air travels through the greenhouse | Can provide more distributed evaporative cooling when correctly designed |
| Selection | Should be based on climate, greenhouse geometry, crop requirements and project economics | |
How Does Shading Reduce Greenhouse Cooling Demand?
Solar radiation is one of the main sources of heat entering a greenhouse.
Shading systems can reduce part of this solar load before the heat must be removed by ventilation or mechanical cooling.
The appropriate shading strategy depends on crop light requirements, greenhouse covering, regional solar conditions and the other climate-control systems installed in the facility.
Excessive shading should also be avoided because reducing heat gain must be balanced against the crop's light requirements.
Why Is Airflow Important in Greenhouse Cooling?
A cooling system can only perform effectively when cooled air reaches the intended production zones.
Crop density, structural components, screens and greenhouse geometry can all create resistance to airflow.
Poor airflow can cause temperature differences between greenhouse areas even when total cooling capacity appears sufficient.
Internal circulation fans can also be used to improve air distribution, but circulation should not be confused with actual ventilation.
Which Sensors Are Used for Greenhouse Cooling Automation?
Indoor Temperature
Determines whether greenhouse cooling equipment should be activated.
Relative Humidity
Helps evaluate evaporative cooling conditions and internal humidity.
Outdoor Temperature
Provides context for determining whether ventilation or evaporative cooling is appropriate.
Equipment Feedback
Confirms whether fans, pumps and other cooling equipment are operating correctly.
Measurement accuracy also depends on installation location. See our greenhouse sensor placement guide for more information.
How Is Greenhouse Cooling Automated?
Greenhouse automation can combine temperature, humidity, ventilation and equipment status within the same control strategy.
Climate Is Measured
Indoor and outdoor temperature and humidity are continuously monitored.
Cooling Demand Is Evaluated
The controller compares measurements with configured climate targets.
Equipment Is Activated
Ventilation, fans, pumps or fogging systems operate according to the selected control strategy.
Performance Is Checked
Temperature response, humidity and equipment feedback are monitored after cooling begins.
These systems can operate as part of a broader greenhouse climate control automation strategy.
Common Greenhouse Cooling Design Mistakes
Ignoring Local Humidity
Evaporative cooling performance changes significantly according to outside-air moisture conditions.
Incorrect Fan or Pad Sizing
Insufficient airflow or unsuitable pad area can reduce cooling performance.
Ignoring Airflow Resistance
Crops, screens and greenhouse geometry can restrict movement of cooled air.
Cooling Without Climate Coordination
Cooling, ventilation and humidity control should not operate as unrelated systems.
Cooling Systems in Turnkey Greenhouse Projects
Greenhouse cooling requirements should ideally be evaluated together with structure, ventilation, shading, heating and automation.
Within Agroteknik's turnkey greenhouse projects , summer climate conditions, ventilation openings, evaporative cooling, sensors and automation can be considered during the same engineering process.
This allows the cooling strategy to be coordinated with greenhouse geometry and the other environmental-control systems from the beginning.
Plan Your Greenhouse Cooling System
We can evaluate ventilation, fan-and-pad cooling, fogging, shading, sensors and automation requirements according to your greenhouse structure, location and production model.
