Impact of Urban Morphology on Thermal Comfort of Outdoor Pedestrian Pathways in Singapore

Abstract

Singapore, and regions in the humid tropics at large, have undergone large-scale urbanisation that changed the configuration and urban fabric of its landscapes. In a warm climate ideal for outdoor activities, it is imperative that outdoor thermal comfort and the strategies to improve it is understood and applied in urban designs. In the present thesis, the microclimate conditions of two built pedestrian spaces - a park connector and in a HDB housing estate - were contrasted against an undeveloped rail corridor. The three sites were classified into Local Climate Zones based on their urban morphology. Quantitative and qualitative thermal comfort conditions were then obtained using various rational and direct thermal comfort indices and thermal comfort surveys. Among them, the present thesis adopted and evaluated the Universal Thermal Climate Index (UTCI), for the first time in Singapore. Field measurements in all sites were used as input data for the computation of the indices. Inter-site differences were evident for all microclimate parameters except for wind speeds. Urban geometry and the properties of urban fabric accounted for these differences. On the contrary, sensation votes did not show much difference across urban morphologies, and were most affected by wind, air temperature and sunlight. All indices showed good correlations with sensation votes, with UTCI and Physiological Equivalent Temperature (PET) index having the strongest relationships. However, all of them overestimated heat stress conditions in Singapore. This thesis concluded that psychological factors influenced thermal sensations, and more work should be done to uncover these factors thoroughly in the humid tropics. UTCI also shows huge potential to be further used in Singapore.