Night ventilation in urban environment.

This study investigates the application of night ventilation techniques in ten urban canyons, situated in the extended region of Athens, Greece. In order to determine the impact of the urban environment on the night ventilation performance, the outdoor air temperature and wind profile have been measured inside and outside the experimental canyons. The application of the night ventilation techniques has been studied in a typical single zone room and various simulations have been performed under controlled and free-floating operation, when single-sided and cross ventilation are considered, during the night period. The influence of the urban microclimate on the efficiency of the technique has been studied by considering the examined zone inside and outside the experimental urban canyons. The comparison of the results permits to evaluate the impact of the urban canyons on the effectiveness of the night ventilation techniques. The performed analysis shows that due to the increase of the air temperature and the decrease of the wind velocity inside the canyons, the potential of the studied techniques can be reduced significantly.