EFFECTS OF URBAN GEOMETRY ON THERMAL COMFORT IN WARM-HUMID CLIMATE

ABSTRACT

The thesis addresses the contributions of urban geometry under warm-humid climate condition in the City of Mombasa, Kenya, toward; the development of comfortable microclimate conditions in outdoor spaces at pedestrian level. The urban geometry is described in this thesis by three variables, including (a) building height to street width aspect ratios (H/w), (b) sky view factor (SVF) at pedestrian level, and (c) the solar orientations of the urban canyons. These three variables are used in this study to investigate their influence on the microclimate conditions and the associated outdoor thermal comfort and energy consumption from urban dwellers.

The work intends to shed light on the existing geometries of different urban locations in the City of Mombasa and the associated thermal conditions, as well as the thermal perceptions and preferences of outdoor users. Therefore, integrated empirical studies that are composed of surveys carried out, a study of Air Temperature of the City of Mombasa and outdoor thermal comfort survey in different urban locations at neighbourhood scale and within urban canyons.

Following that, microclimate modelling are carried out on a number of hypothetical urban geometries that were proposed according to the current buildings and planning regulations in the City of Mombasa, i.e. building materials, opening ratios on building facades, buildings and streets layouts and minimum width of local streets. Yet, since the study measures the impact of scenarios modifications of urban geometry on the issues under investigation, thus, additional buildings heights and different setback aspect ratios have been added. The proposed hypothetical urban geometries investigated include various street aspect ratio (H/st.) equal to 0.5, 1, 1.5 and 2, and setback aspect ratio (H/sb.) equal to 0, 2, 4 and 8. The proposed urban settings that resulted from the combination of the various streets and setbacks aspect ratios are modelled on two different orientations, including EW and NS.

The microclimate modelling reveal a clear impact of canyons’ geometry on the outdoor thermal comfort at pedestrian level. In all of the proposed urban settings of pavilion building typology, the setback aspect ratios proved to have an important role in determining the issue in study. The NS oriented canyons show some advantage over the other orientation studied EW. This is expressed by a shorter duration of exposure to solar radiation at street level.

The conclusions derived from the microclimate measurements and from the microclimate modelling point out the necessity for promoting shading and radiative cooling in urban design to keep the external microclimate conditions in comfort range and to minimise the energy consumption from urban buildings.

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Pages from 6th Thesis- Kimethu-C-Kyalungu.pdf4.16 MB

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