School buildings in Italy traditionally haven’t a cooling plant as during the peak summer period they are closed. Otherwise nowadays the teaching period has been expanded and the classrooms in many cases are used also for recreations of pupils free from school by local authorities. During months like June or September also in North Italy are present periods of high diurnal temperature and humidity. Consequently at least in the design of new school building some kind of cooling strategy is needed and considering the limited economic budget for functioning of this kind of institutions have to be low energy demanding. In this context night natural ventilation seems a promising solution able to provide cooling when requested. Even if its cooling capacity is limited, an optimized design process can lead to comfortable and controllable conditions for the occupants and can reach relevant decreases in energy consumption. As a case study the authors assumed the design of a new school building near Treviso in the North-East Italy. The purpose of the work is to analyse for northern Italian climate the performances of natural ventilation strategies such as stack chimney effect and wind induced cross ventilation by means of computational fluid dynamics simulation (CFD). Through a climatic analysis the mean wind directions and velocities and the mean ambient temperature fluctuations have been calculated. After the climatic analysis a urban CFD simulation has been performed to investigate wind behavior near the school building. A first design step was the sizing of openings and ventilation chimney by means of normographs and after that an internal CFD simulation has been performed with the aim of evaluate air flow patterns inside the classrooms. Vent placement and ventilation chimney shape and height have been verified and optimized considering a night ventilation flow pattern during summer. The internal analysis has highlighted that during a typical summer night the air moves across the school room entering from the bottom window and going out from the top chimney, providing an air changes value of 9 volumes per hour. This night summer air flow pattern lead to a surface temperatures reduction of about 2,2°C and to an air temperatures reduction of about 4,7°C.
Improvement of natural ventilation as passive design strategy in a school building
PERON, FABIO;MAZZALI, UGO;ROMAGNONI, PIERCARLO
2011-01-01
Abstract
School buildings in Italy traditionally haven’t a cooling plant as during the peak summer period they are closed. Otherwise nowadays the teaching period has been expanded and the classrooms in many cases are used also for recreations of pupils free from school by local authorities. During months like June or September also in North Italy are present periods of high diurnal temperature and humidity. Consequently at least in the design of new school building some kind of cooling strategy is needed and considering the limited economic budget for functioning of this kind of institutions have to be low energy demanding. In this context night natural ventilation seems a promising solution able to provide cooling when requested. Even if its cooling capacity is limited, an optimized design process can lead to comfortable and controllable conditions for the occupants and can reach relevant decreases in energy consumption. As a case study the authors assumed the design of a new school building near Treviso in the North-East Italy. The purpose of the work is to analyse for northern Italian climate the performances of natural ventilation strategies such as stack chimney effect and wind induced cross ventilation by means of computational fluid dynamics simulation (CFD). Through a climatic analysis the mean wind directions and velocities and the mean ambient temperature fluctuations have been calculated. After the climatic analysis a urban CFD simulation has been performed to investigate wind behavior near the school building. A first design step was the sizing of openings and ventilation chimney by means of normographs and after that an internal CFD simulation has been performed with the aim of evaluate air flow patterns inside the classrooms. Vent placement and ventilation chimney shape and height have been verified and optimized considering a night ventilation flow pattern during summer. The internal analysis has highlighted that during a typical summer night the air moves across the school room entering from the bottom window and going out from the top chimney, providing an air changes value of 9 volumes per hour. This night summer air flow pattern lead to a surface temperatures reduction of about 2,2°C and to an air temperatures reduction of about 4,7°C.
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