Towards Better Urban Spaces in Harmony with Microclimate: Urban design and planning regulations in hot dry Damascus, Syria

Abstract: This research is an attempt to develop further understanding of the relationship between microclimate, thermal comfort, urban design and outdoor space users 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 Damascus. This study also aims to investigate the behaviour of different thermal comfort indices and defines the thermal comfort limits for Damascus in the summer and winter seasons. In addition, understanding how to apply the knowledge of urban microclimate and thermal comfort in the urban design process is also a part of the aim. The study analyzes and climatically examines the urban planning regulations through simulations. In addition, micrometeorological measurements and structured interviews in different urban environments are carried out in the summer and winter seasons. The study deals with attached (Old Damascus) and detached building geometries (modern Damascus). However, it focuses more on modern Damascus to develop the thermal environment in both existing and future urban spaces. By combining the results of measurements and structured interviews on people’s subjective thermal perception, the upper and lower thermal comfort limits for two thermal comfort indices – the physiologically equivalent temperature (PET) and the standard effective temperature for outdoors (OUT_SET') – are defined for summer and winter respectively. Furthermore, a parametric study was carried out using the microclimate simulation programme ENVI-met. Modelling and simulations were conducted for summer and winter in order to study how to improve the outdoor thermal comfort in Damascus by investigating different urban design scenarios and using different landscape elements in simulations carried out during the different hours of the day. In order to investigate how the urban design in Damascus could be adapted to the microclimate and outdoor thermal comfort, an evaluation of an urban design proposal is done from a thermal comfort point of view through simulations where the thermal comfort limits are applied. The study concludes that 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 yards. In the case of urban canyons, the study confirms that the aspect ratio, street orientation, and vegetation are very important in street design. On the other hand, in urban environments consisting of detached buildings as in modern Damascus, the influence of street orientation and aspect ratio on surface temperatures and outdoor thermal comfort is less important, whereas the use of vegetation may reduce surface temperatures and improve the outdoor thermal comfort substantially. For future urban residential areas in Damascus, it is therefore important to update the existing urban planning regulations according to the climatic requirements. This can be done by reducing front and side setbacks or to have none at all, planning narrower streets, increase the maximum number of floors permitted, and allowing projections of upper floors. Moreover, architectural design elements, which provide shade for pedestrians at street level such as balconies and arcades, ought to be used more. In addition, outdoor thermal comfort in existing urban areas in modern Damascus could be improved by introducing vegetation and landscaping in the urban design process. It is therefore important to create a link between landscape design and urban planning regulations. Such a link could be as a set of guidelines for street design and plant selection, i.e. choosing the right type of vegetation and using non-evergreen trees that can provide shade in the summer and help the solar radiation to reach the ground in the winter.