As outdoor temperatures change throughout the year, buildings need flexible cooling strategies to maintain a comfortable indoor climate without unnecessary energy consumption. Free cooling offers a simple, dynamic and energy-efficient solution by using naturally cool outdoor air to remove excess heat from a building, instead of relying exclusively on mechanical cooling systems. It provides a practical solution for offices, commercial buildings, industrial facilities and other spaces equipped with mechanical ventilation.
Free cooling can operate as the primary cooling method, or work alongside mechanical cooling systems such as air conditioning. By combining both approaches, buildings can make better use of available outdoor conditions while reducing reliance on energy-intensive cooling equipment.
Free Cooling vs. Air Conditioning: What's the Difference?
Both free cooling and air conditioning help reducing indoor temperatures, but they use very different methods.
Air conditioning uses mechanical cooling as a refrigeration system actively removes heat from the air, allowing the indoor temperature to be reduced even when the outdoor air is too hot for free cooling.
Free cooling, on the other hand, does not require compressors or refrigeration circuits to cool the incoming air first. The ventilation system uses the cooling potential of outdoor air. When it is cooler than the indoor air, the ventilation system increases the supply of outdoor air to remove excess heat from the building.
This means that free cooling is dependent on outdoor conditions, while air conditioning can provide cooling independently of the outdoor temperature.
The two methods do not have to operate separately, but can complement each other. When outdoor conditions are favourable, free cooling can reduce or even eliminate the need for mechanical cooling. When outdoor air is no longer cool enough, the system can switch to mechanical cooling, if required.
Smart Control for Energy-Efficient Cooling
Cooling buildings can account for a significant share of their energy consumption, particularly during warm weather and periods of high occupancy. Free cooling helps reduce this demand by using the naturally available cooling capacity of outdoor air. When outdoor air is sufficiently cool, the ventilation system can take over (part of) the cooling demand. This reduces the need to operate compressors and other mechanical cooling equipment.
The main benefits include:
- Lower energy consumption: reduces reliance on mechanical cooling equipment when outdoor conditions are suitable
- Reduced cooling costs: makes use of naturally cool outdoor air to limit the use of energy-intensive cooling systems
- Reduced mechanical cooling load: helps air conditioning systems operate less frequently or for shorter periods
- More efficient ventilation: allows the ventilation system to contribute actively to temperature control, rather than only supplying fresh air
- Improved comfort: helps maintain a comfortable indoor temperature when free cooling is properly controlled
Free cooling is not suitable under all outdoor conditions. If the outdoor air is too hot, supplying more of it may increase the indoor temperature instead of reducing it. A ventilation system therefore needs to determine when free cooling is beneficial and when another cooling strategy is required.
A free cooling controller continuously monitors relevant temperature conditions and automatically adjusts the ventilation system accordingly. This helps ensure that free cooling is activated when outdoor air can provide a useful cooling effect and deactivated when conditions are no longer favourable. Intelligent control also helps prevent unnecessary fan operation and ensures that the cooling strategy adapts to changing indoor and outdoor temperatures.
Free cooling is particularly useful during spring and autumn, cool summer nights and other periods when outdoor air is cooler than the indoor environment.
Free Cooling Controller: Cool by Nature
Sentera’s FCCA8-DM free cooling controller is designed for ventilation and cooling applications in offices, commercial and industrial buildings. The controller combines continuous temperature monitoring, automatic fan speed control and flexible communication options in one solution. The FCCA8-DM enables ventilation systems to respond to changing thermal conditions, making free cooling part of an efficient ventilation strategy and supporting optimal building performance.
How does this free cooling controller work?
This controller continuously monitors indoor and outdoor temperatures using two PT500 temperature sensors. By comparing both temperatures, it determines when outdoor conditions are suitable for free cooling and adjusts the ventilation accordingly.
The controller supports two fan speed control modes. With Variable Fan Speed Control, the fan speed is automatically adjusted in steps according to the temperature difference between indoor and outdoor air. With Fixed Fan Speed Control, the fan operates at a preset speed whenever free cooling is active.
A Boost function can temporarily increase the fan speed when a quick air refresh is needed. For situations that require manual intervention, an Override Control function allows the automatic settings to be bypassed.
It also features a configurable analogue output, supporting 0–10 VDC, 4–20 mA or PWM, making it suitable for different motors with an analogue input. The relay output can be used to control auxiliary equipment.
The controller can be integrated into a Building Management System (BMS) via Modbus RTU, providing access to measured values, operating status and settings.
Want to let nature do the cooling?