This paper presents an up-and-running control system, using IoT hardware, for multiple decentralized mechanical ventilation with heat recovery (dMVHR) units to enhance the overall performance of heat exchangers and the air quality of a real-life environment. The implemented control and monitoring system is able to measure the thermal efficiency of the complete ventilation system under real working conditions. Fan speed is automated based on the measured CO2eq levels in the bedrooms of the building, however, manual control is also possible. Temperature, relative humidity and CO2eq levels can be monitored live on the user’s smart device, while data can be exported through Google cloud system. Data values can be stored and accessed any time by legit users. The thermal efficiency of the individual units and the whole ventilation system was investigated and experimentally verified under real-life conditions, using the implemented centralized control and monitoring system.