Microclimate and Thermal Comfort of Urban Spaces in Hot Dry Damascus- Influence of urban design and planning regulations

Abstract: The aim of this study is to develop better understanding of the relationship between microclimate and urban design in the hot dry city of Damascus. This is done by studying the impact of urban regulations on microclimate in different urban design patterns in modern Damascus. This study also investigates the behaviour of different thermal comfort indices to define the thermal comfort and acceptability limits of some of these indices. These limits, in turn, will help architects and designers to create better urban spaces by taking microclimate and thermal comfort requirements into account. The study analyzes and climatically examines the urban planning regulations by using simulations. In addition, microclimatic measurements and structured interviews in different urban environments are carried out. The study highlights the importance of microclimate and thermal comfort in the planning and design processes and it provides useful insights that can mitigate the negative aspects of urban design on microclimate and thermal comfort in Damascus. The simulations reveal the shortcomings of the current planning regulations in Damascus city as regards the outdoor thermal comfort at street level in the summer time. The regulations for modern Damascus prescribe wide streets and pavements, large setbacks and relatively low building heights. This leads to a dispersed urban form where a large part of the buildings and streets are exposed to solar radiation. The existing planning regulations in Damascus have no requirements for shading for pedestrians, e.g. shading devices, arcades and projecting upper floors or shading trees. Apart from leading to poor microclimatic conditions in the summer, land use in the modern part of Damascus is highly inefficient, with a disproportionately large amount of ground occupied by streets, pavements and front yards. In order to increase shade at street level in future urban areas in Damascus, it is important to develop the existing urban planning regulations according to the climatic requirements. This can be done by reducing front setbacks or to have none at all, planning narrower streets, increase the permissive maximum number of floors, and allowing projections of upper floors. Moreover, the use of vegetation would also have a positive influence on the air quality as well as the quality of life. It is therefore important to create a link between urban landscape and urban planning regulations. Such a link could be as a set of guidelines for street design and plant selection. Field measurements and structured interviews assess the microclimate of the outdoor urban environment and investigate the relationship between different thermal comfort indices and people’s actual thermal sensation in Damascus. In general, areas that provide shade – either by buildings, such as Old Damascus, or vegetation – are more comfortable in summer than in winter. Conversely, street canyons and parks in modern Damascus, which are open to solar access, are more comfortable in winter than in summer. Furthermore, this study defines the summer and winter comfort zones and acceptability limits for PET and OUT_SET' in hot dry Damascus. The results highlight the importance of a climate-conscious urban design and design flexibility. It is important to consider microclimate and thermal comfort in the urban design process. This can be done by providing a basic knowledge for architects, designers, and planners about the importance of microclimate and thermal comfort and how to create better urban spaces in harmony with climate. Based on such knowledge, summer and winter comfort zones and acceptability limits for Damascus can be understood and promoted as a goal to design better urban spaces by taking these limits into account.

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