ICUC8 – 8 th International Conference on Urban Climates, 6 th -10 th August, 2012, UCD, Dublin Ireland. 347: An analysis of the effects of shading factors on human bioclimate in an evolving urban context Tzu-Ping Lin 1 *, Kang-Ting Tsai 1 , Chien-Hung Tung 1 , Ruey-Lung Hwang 2 , Andreas Matzarakis 3 Program of Landscape and Recreation, National Chung Hsing University, Taichung, Taiwan 1* tplin@dragon.nchu.edu.tw Department of Architecture, National United University, Taiwan 2 Meteorological Institute, Albert-Ludwigs-University Freiburg, Freiburg, Germany 3 This study analyzes the results of field experiments on the effects of outdoor thermal conditions on urban streets in Central Taiwan and considers long-term thermal comfort based on meteorological data. Results indicate that areas with slight amounts of shade typically experience frequent hot conditions during summer, particularly at noon. However, highly shaded locations generally show a low physiologically equivalent temperature (PET) during winter. Correlation analysis shows that thermal comfort is greater when a location is shaded during spring, summer, and autumn. Furthermore, historical data and current observations of the evolution of urban context in Taiwan show that the formation of current unpleasant thermal environments of urban street patterns in old townships of Taiwan has an historical legacy that affects opportunities for street businesses. We suggest that a specific shading level is ideal for urban streets, and trees or shade devices should be employed to improve the existing thermal environment. Keywords: thermal comfort, bioclimate, urban context 1. Introduction The outdoor thermal comfort of people is affected by the thermal environment. Moreover, their use of outdoor environments is affected by their perception of outdoor thermal conditions [1-5]. Furthermore, outdoor thermal environments are affected significantly by the design of urbanised environments [6]. Because shading can block direct solar radiation, numerous studies have examined the effects of shading on outdoor thermal environments. For example, previous studies [7-11] quantified the height/width (H/W) ratio of urban streets to assess shading levels, whereas the sky view factor (SVF) was used in other studies to represent shading levels [12, 13] Buildings on Taiwan’s traditional streets are mostly a combination of residential and commercial (i.e., the first floor is rented by stores and the upper floors are residential). Buildings that are not designed to include an arcade on the ground floor result in insufficient shading, and people are forced to walk beside the street when shopping, thereby exposing them to the outdoor climate. Thus, people may be dissatisfied with their shopping experiences when they feel uncomfortable in an outdoor thermal environment, adversely affecting store revenue and reducing rental prices. Therefore, investigating thermal comfort on urban blocks is essential to the economy. The objectives of this study are to (1) conduct a field experiment in traditional urban streets in Taiwan; (2) establish a prediction model for thermal environments based on the long-term meteorological data; (3) evaluate the long-term thermal comfort frequencies based on the local thermal comfort criteria; and (4) examine the seasonal effects of urban street shading on long- term outdoor thermal comfort. 2. Method 2.1 Outdoor thermal comfort indices Physiologically equivalent temperature (PET) is defined as air temperature (Ta) that, in a typical indoor setting (Ta = Tmrt; vapor pressure (Vp)=12 hpa; and wind speed (v) = 0.1 m/s), balances with the heat budget of the human body (i.e., identical core and skin temperature as those under complex outdoor conditions [14, 15]. In this study, PET is applied as the main thermal comfort index because it can be estimated using the RayMan model and has been used in developed urban areas to generate predictions of thermal comfort in outdoor environments [16- 19]Additionally, the sky view factor (SVF) (i.e. the ratio of free sky spaces to the entire fisheye view) at a specific location can also be calculated using the RayMan model for subsequent analyses. 2.2 Local thermal comfort criterion for PET Previous studies examining thermal adaptation indicated that occupant thermal sensations and preferences vary considerably because of differences in behavioural adjustment, physiological acclimatization, and psychological habituation or expectations [20] All of these factors may contribute to different thermal comfort ranges (i.e., the range of thermal indices at which people feel comfortable). Therefore, the thermal comfort range for a particular region may be inapplicable to other regions. In this study, the thermal comfort range is obtained from a field