Indoor Air Quality
Fresh air supply is essential to create a healthy and comfortable environment. Since most people spend the majority of their time indoors, indoor air quality has a direct impact on their health. Together with the increased thermal insulation of our buildings, the importance of ventilation systems is rising in order to maintain a good indoor air quality.
Temperature, relative humidity, CO2 and TVOC are the most important parameters that determine an occupant's comfort and productivity. For more information about indoor air quality, it is advisable to visit www.air-quality-monitor.eu
When many people share a confined space, fresh air supply will be maximised in a well-dimensioned ventilation system. The fan speed and thus the air volume flow will reach their maximum level. This is necessary to guarantee a good indoor air quality and to keep the CO2 and TVOC concentrations at an acceptable level. When fewer people are present in the same room, a lower supply rate of fresh air will be sufficient. This variable regulation of the ventilation system will increase the comfort of the residents and save energy.
COVID-19 contamination via aerosols
The risk of becoming infected with the COVID-19 virus is higher in crowded and poorly ventilated spaces. Transmission of COVID-19 via aerosols rarely occurs outdoor or in enclosed spaces with a large volume. Some ventilation systems partially recover indoor air to minimise heat losses. This internal air circulation can spread viruses through the building. Therefore, the general recommendation is to deactivate indoor air recirculation, to increase the supply rate of fresh air and the extraction rate of stale air. The ventilation system should remain active on a continuous basis. Most ventilation systems are dimensioned to provide crowded spaces with sufficient fresh air. When the room is not occupied, the air volume flow rate can be reduced while still supplying sufficient fresh air.
What is the advantage of an apparently complex fan speed controller? Why not run the fans continuously at maximum speed? Then there is certainly sufficient fresh air supply… A slight reduction in fan speed has a major impact on the electrical energy consumption of the fan. A typical HVAC fan follows a quadratic torque curve. Depending on the motor type, a reduction of 25 % air volume flow corresponds with 50 % less energy consumption. In addition, a lower air volume flow rate also results in a quieter operation.
Input power (%)
Flow rate (%)
Minimise heat losses
In colder or moderate climates, extracted warm indoor air is replaced by fresh, colder air. The less warm indoor air has to be replaced by cold outdoor air, the lower the heat loss. Modern ventilation systems are nowadays equipped with a heat exchanger to minimize such heat losses. Nevertheless, additional energy can be saved by reducing the fan speed when possible. By measuring the air quality of the extracted indoor air, the fan speed can be continuously optimised while the indoor air quality is guaranteed.
Extended service life
Air filter service intervals are significantly extended by reducing the air volume flow rate. The more air that passes through the filters, the higher the risk of contamination of the filters. A reduced air volume flow rate also has a positive effect on the service life of the mechanical parts of the fan. These prolonged service intervals reduce the operational costs and the total cost of ownership.