## 5 Case Study: Cuza School Pilot School
Medium and fine dust filters (M6, F7, F8) are optional for this system, to meet customer requirements or applicable legislation. The installation time was short due to the easy adjustment of the nominal air flow--in our case a 1 day installation; therefore, fewer air dampers are required than in the case of traditional installations. It can work in conditions of overpressure and depression. The system is installed with two filters, G3 + F7, with automatic switching of heat-recovery units to a free cooling mode in the event of high heat, and has a cost of 3400 \(\upcels/\)unit (without VAT) + C147 for filters and has operating temperatures from \(-\)15 to 50 \(\upcels/\)C. The introduction of fresh air was performed using textile piping (see Figure 2), while the extraction was performed using steel classic ventilation ducts. The second system (see Figure 3) is also a decentralized ventilation unit with a high heat-recovery efficiency (up to 93% according to technical specifications), low noise levels, low installed power consumption, and minimal installation requirements. The equipment is equipped with an aMotion control module to operate all the necessary functions and consists of flexibly mounted inlet and suction fans, a countercurrent heat-recovery exchanger, a sliding supply air filter, a bypass flap for the heat exchanger, autonomously operated closing flaps, and a control box. The condensation tray (no drain) is heated using an electric cell with an automatic switching function. The upper section is equipped with noise attenuators with separation, grilles for the exhaust and intake of air, a filter for the extracted air, and an external CO\({}_{2}\) concentration sensor. The lower part of the unit has a spacer frame made of anti-vibration rubber. This system was also installed in one day and was connected to Wifi for control. Compared to the previous solution, it has the disadvantage that it is occupying around 1 m\({}^{2}\) in the back of the room, but on the other hand, it is well fixed to the wall and in case of earthquakes (Bucharest has a high risk), the system is secured with no danger for the children. Figure 1: (**a**) External photo of the pilot school. (**b**) Typical classroom. The third system is a decentralized mechanical ventilation system consisting of two HRV ventilation units and one ERV ventilation unit installed in a classroom number (3)--see Figure 4. The systems are smaller and are decentralized ventilation systems, including a heat-recovery system from the exhausted air, thus reducing energy consumption for heating or cooling the outside air. Integrated CO\({}_{2}\) sensors enable the continuous monitoring of carbon dioxide concentrations in the classroom. When the CO\({}_{2}\) concentration exceeds a preset level, the ventilation system automatically activates, ensuring a constant supply of fresh air. The outside air introduced is preheated by means of an electric resistance and reheated with the help of a battery fed with hot thermal water (supplied by the heating network of the city of Bucharest). The systems not only allow for the introduction of fresh filtered air but also act as radiators for the heating. Clearly, its main advantages is the fact that it does not reduce the area and is also fixed to the wall, making it safe. While two HRV units were placed left and right of the room, in the middle, the ERV unit was installed and equipped with an advanced energy-recovery system, known as enthalpy recovery, which allows for the transfer of not only heat, but also moisture between the exhaust air and the air introduced into the classroom. Through this process, the ERV Decentralized Ventilation System ensures more the efficient regulation of humidity inside the classroom. Thus, the state of thermal comfort is improved, not only by maintaining a constant temperature, but also by controlling the humidity, which has a positive impact on the performance of the occupants.