One of the most important factors for increasing productivity in animal husbandry, poultry farming, and in greenhouse complexes, including for growing mushrooms, is the microclimate. To ensure normal air exchange in agricultural premises, roof fans with horizontal discharge of the VKR-4 type are recommended and used. When using ventilation equipment, it is necessary to take into account the technological requirements for creating a microclimate and the capabilities of the equipment. (Research purpose) The research purpose is in justifying the rational parameters of the system for creating a microclimate in agricultural premises when using a fan of the VKR-4 type, and to give recommendations to the agricultural producer. (Materials and methods) Authors investigated the efficiency of regulating the performance of the ventilation system by means of a valve in the exhaust shaft of the ventilator and by changing the supply voltage of the electric motor. (Results and discussion) The article presents experimental studies of the operation of the ventilation system when using a roof fan of the VKR-4 type to determine its effectiveness in order to maintain the required zootechnical parameters in rooms for keeping animals at the lowest energy costs. (Conclusions) Regulating the performance of the ventilation unit by means of a mechanical flap in the exhaust shaft of the fan by changing the angle of its opening is uneconomical. The regulation by reversing the electric motor provides a 1:2 ratio of the air supply, but the power consumption of the electric motor increases almost twice during the reverse. When the fan performance is controlled by changing the motor voltage from 70 to 173 volts of line voltage, the performance increases, but with a further increase in voltage, it does not change, and the power consumption continues to increase.