Investigating potential of natural driving forces for ventilation in four major cities in China

The potential of natural driving forces for ventilation in buildings is the possibility for providing sufficient outdoor air by only natural ventilation. Based on the early work of Fracastoro et al. (Fourth international conference on indoor air quality, ventilation and energy conservation in buildings-IAQVEC, vol. III, Hong Kong: The City University of Hong Kong; 2001. p. 1421-9.), we develop a simple prediction model for this natural ventilation potential applicable to Chinese residential buildings, using a simple analytical model of natural ventilation considering the combined effect of wind and thermal buoyancy forces. Comparing with the existing method developed by Fracastoro et al. (2001), the present prediction does not need sophisticated multi-zone modeling calculations and the constants in the model are no longer variables. Using the weather data from International Weather for Energy Calculations (IWEC) into our simple prediction model, the natural ventilation potentials for low-rise residential buildings in four representative cities of China including Beijing in the north, Shanghai in the east, Guangzhou in the south and Urumqi in the northwest were analyzed. We introduced the concept of the pressure difference Pascal hours (PDPH) for natural ventilation, and PDPH was calculated and compared for four cities. A high PDPH value means a great potential for application of natural ventilation. In addition, hourly effective pressure differences can be obtained and analyzed statistically. This information can help the designers to determine the building opening size, or to assess whether or when mechanical ventilation is necessary. The application of the model can be a simple design tool at preliminary design stage.