Control strategies of the natural ventilation for passive cooling for an existing residential building in mediterranean climate

Natural ventilation is increasingly considered one of the most efficient passive solutions to improve thermal comfort in buildings. However in order to support its planning and implementation, quantitative analysis on airflow paths and heat-airflow building interactions are needed. This requires an adequate accounting of both internal effects, from building layout and structure, and external forcings from atmospheric factors. This paper has dealt to analyze the potential of building automation systems for ventilative cooling of residential buildings. The case study focused on a Italian typical building of the '60s, situated in the Mediterranean climatic context (Bari - Italy, 41° 07'31 "N 16 ° 52'00" E, 5 m asl), with windowed sides faced to northwest and southeast. Various operating controls of ventilation have been developed to reduce energy consumption for cooling, ensuring adequate levels of indoor comfort. In particular, automated bottom hinged windows have been hypothesized. Different design solutions have been simulated in order to choose the optimal control of ventilation in relation to internal and external temperature and humidity (relative and absolute). The air flows in the building have been calculated with a multizone airflow model, performed by TRNFLOW within the TRNSYS software. Thermal comfort analysis, according to the adaptive thermal comfort theory (EN 15251-2007), have shown that a natural ventilation system, calibrated on a variable set-point based on the optimal temperatures (according to the theory of adaptive comfort) determines a significant reduction of overheating during the occupation hours. Despite the benefits of such control logic, it has been necessary to provide a second control logic, calibrated on internal and external humidity (relative and absolute). The simulations results have underlined a significant reduction in relative humidity levels (generally in range 40- 60%), although some undercooling occurs due to the opening of the windows when the control on the temperature is set off. Others simulations have regarded the combination of the above described natural ventilation system, with an air to air heat pump. The simulation results have showed that the control strategies of ventilation for passive cooling enable significant reduction in energy consumption. This study have underlined that ventilation strategies for passive cooling of existing buildings in Mediterranean climate, can contribute even more effectively to the improvement of the behavior of the building envelope,integrating or replacing the conventional efficiency strategies, if properly integrated with adequate control systems