The impact of urban form and shading on microclimate and indoor air temperatures of dwellings: a case study of Erbil, Kurdistan, Iraq

Abstract

PhD ThesisThe history of the Kurdistan region of northern Iraq is complex, however it was established as an autonomous region (Kurdistan‐Iraq) in 1991, since when it has flourished in stark contrast to the remainder of Iraq and Syria. The capital of Kurdistan is the historic city of Erbil one of the most ancient cities in the world (with at least 4000 years of history). In recent times, the city has expanded dramatically after 2003, in a series of concentric rings around the central ancient Citadel, to accommodate Kurds from both Kurdistan‐Iraq and the returning diaspora. This rapid urban expansion has turned its back on the traditional design principles of the ancient Citadel which was designed to work in harmony with the hot dry climate; organic designs of narrow, winding streets designed around the needs of the pedestrian. Instead this organic morphology has been replaced by grid‐iron planning, with street widths designed to accommodate motor vehicles. The alignment of these grid‐iron street patterns has been driven by geometry rather than referencing urban micro climatic needs. The main aim of this research is to investigate the impact of urban form and shading on the urban micro climate and the indoor air temperature of dwellings in the new (post 2003) developments of Erbil. To achieve these aims two methods were used: The prediction of the urban micro climate used ENVImet, a numerical climate simulation program. The indoor air temperatures were predicted using the building energy simulation software IES Virtual Environments (IES‐VE). The climate modelling compared traditional and grid‐iron morphologies and demonstrated that the traditional morphology produced lower external air temperatures. For the modern grid‐iron morphologies, higher wind speeds in the urban canyons were achieved when the prevailing wind from the South West flowed through a canyon grid aligned North‐South and East‐West. Shading by both trees and wire mesh was modelled. Both reduce the external mean radiant temperature, but have little impact on the external air temperature. Moreover, the wire mesh shading did not reduce the urban wind speeds, but the tree shading did reduce urban wind speeds. When shading buildings, the reduction in indoor air temperature was small; whilst the shading mesh reduced solar gain it also reduced night‐time losses to the clear night sky, yielding a small reduction in indoor air temperature. However, when purposeful night‐time ventilation was modelled, the reduction in indoor air temperature was significant. By combining building shading (reducing solar gain) and night time purpose ventilation (increasing nigh‐time cooling) allows greater freedom in façade design. This permits modern house design to have a similar thermal performance to the traditional house design. The study has developed a novel method to simulate efficiently wire mesh shading both for urban micro climates and buildings. It has shown how the modern grid‐iron urban morphology can be adapted to provide improved micro climates and how individual houses can be designed to benefit from these changed micro climates. For the future, it is recommended that full scale testing of whole housing shading be undertaken and how this shading can be adapted to reflect the local identity of the region