Natural cross ventilation in buildings on Mediterranean coastal zones

Natural ventilation of buildings is a common way to improve indoor air quality, thermal comfort in summer and reduce energy consumption due to air conditioning. However, efficiency of such a system is highly dependent on climatic conditions. This paper investigates the use of thermal breezes, characterized by moderate speeds and well-defined direction, to improve natural cross ventilation technique on Mediterranean coastal zones. The interest of this phenomenon is highlighted by the development of climate indicators with meteorological data from various places in Corsica (France). A statistical wind rose is used to give more information on main wind sectors and speed fluctuations. The natural ventilation potential is assessed by a radar plot which groups the main climate indicators for comfort ventilation and passive cooling. Tracer gas measurements on a seaside building in Corsica show that high air change rates are reached by cross ventilation during day (higher than 25 ACH). Night ventilation gives more moderate results for passive cooling with air change rates close to 10 ACH. As the comfort in building is related to the airflow, it is necessary to be able to control it. The issue of controlling openings to maintain a satisfying airflow is treated with the help of an empirical model. Due to the regularity of thermal breezes, it shows that even if the airflow varies greatly during the day, a minimal control on opening surface is sufficient to maintain the airflow rate on a comfortable range.