EFFECTS OF BUILDING POROSITY ON NATURAL VENTILATION

Abstract

Wind analysis for urban areas has become a topic of growing importance. As building density increases due to urbanisation, flow retardation resulting in low wind speeds in turn reduces thermal comfort in tropical cities. In Singapore, residential buildings account for about 26% of infrastructure and this number is likely increase in the future due to projected population growth. With thermal comfort being one of the key consideration in the design of HDB flats and enhancement to the wind environment being cited as one of the most important factors in reducing thermal discomfort in the tropics, it is essential for wind studies on the urban climate to be carried out as a reference to shape future urban planning and design. This study aims to examine the relationship between building porosity and natural ventilation through studying residential buildings with void decks and cross ventilated residential units to understand how air flow is affected by the building feature and potential effects on thermal comfort of building occupants. Numerical approach in the form of computational fluid dynamics simulation was conducted to investigate the effects of building porosity on natural ventilation in buildings. Computational fluid dynamics models validated with past literature reviews were used to conduct two parametric studies. The first study compared three cases, an idealised room model (Reference case), one with void deck, one with void deck “filled” with obstruction and showed that void decks provided little to no enhancement to wind speed for natural ventilation in buildings. The second study was carried out on building models of typical height in Singapore, one with void deck and one without. Results showed otherwise and suggest that void decks provides enhancement to wind speed for natural ventilation in buildings. This is due to building height having strong influence in the way wind flows around and within a building. The findings reveal that the introduction of void deck enhances wind speed though limited to the low levels of a building. Flow patterns are also altered, promoting circulation within units on low levels which typically suffers from poor ventilation. The introduction of void deck in buildings is beneficial for achieving indoor thermal comfort in tropical cities.