The EVC (Efficient Ventilation Control) is used to minimize electrical power consumption of fans and thermal energy in a central ventilation system with several rooms or zones and variable volume flows (on demand). The EVC is designed as a control accessory for Systemair Geniox, Topvex and SAVE air handling units. It detects and optimizes the damper position of volume flow controllers in a ventilation system in order to obtain the lowest possible fan speed for each operating status. As a result, the electrical power consumption of the fans and the thermal energy in the ventilation unit decreases. Compared to constant pressure controlled systems, up to 60 % of the energy costs for the fan operation can be saved.