AbstractCurrent global urbanisation rates highlight the need to reconsider our design practices to minimise the negative impacts of our built environments on natural resources and the health and well-being of urban residents. The debate on the sustainability of urban form started decades ago, underpinned by a set of environmental criteria, delineating the path for policy development to find the optimum balance between urban density and the thermal and energy performance. In developing countries, despite their anticipated share of global urban population, this balance is far from being realised. In Egypt, where massive construction projects are being carried out, the vulnerability of urban residents is mostly recognised by the gap between a drastic urban growth and its reflection on the local construction policies, which pay very little attention to the environmental implications of building new conurbations.
This thesis fills this gap by presenting quantitative scientific evidence on the relationship between urban form and both thermal comfort and energy performance in buildings, in Cairo, Egypt. In doing so, the thesis introduces a simulation workflow within the parametric design interface, Grasshopper for Rhino3D, to investigate the impact of various urban geometry configurations on different environmental performance criteria, studied within three key milestones. The performance criteria are outdoor thermal comfort, represented by the Universal Thermal Climate Index (UTCI), and the total energy loads in buildings. First, 7716 urban street canyon configurations are studied though varying their design parameters in three consecutive phases, to maximise outdoor thermal comfort. Simulations includes changing 12 heights of canyon’s flanks simultaneously and separately, 11 street widths, and 12 different orientations of the street canyon. The results reveal new correlations between the design parameters and thermal comfort, showing the ability to reduce thermal stress beyond the design thresholds of local construction codes, which reaches up to 6° C, thus highlighting the need for climate-sensitive design regulations.
Second, 3430 typological and morphological design configurations are investigated on an urban block scale through varying their design parameters, to find the best typology and its associated density parameters which maximise outdoor thermal comfort and minimise energy loads.
Simulations includes changing 10 building heights, 7 different orientation of the urban block, and 7 street widths in each direction (NS and EW). The results show that compact and medium density urban configurations correspond to the best trade-off between the performance criteria, also indicating a relative outperformance of the courtyard typology.
Finally, the environmental performance of the courtyard block typology is revisited to investigate the potential improvements in outdoor thermal comfort and energy loads by changing the heights of individual buildings. Simulation included varying 3 street widths, 4 different orientations of the courtyard blocks, and 3 heights for each building within a single courtyard block. The results show that courtyard blocks perform best when they have minimum interspaces, orientated NE-SW or NW-SE, where their northern and southern buildings are relatively higher than the eastern and western buildings. The results also shows that vertically heterogeneous configurations have the potential to improve both performance criteria, as compared to conventional courtyard blocks, highlighting the need for deliberate passive solar design, as well as the need to bring vernacular design traditions back into practice.
The findings of this thesis can help shift the current design practices in Egypt towards achieving a climate-responsive urban form, in line with ambitious national goals – Egypt’s Vision 2030. The thesis contributes to the scientific knowledge through defining design guidelines for urban built forms in extreme and typical hot-arid climate conditions, considering outdoor thermal comfort and energy loads, which are significantly correlated to the urban heat island mitigation. Also, the thesis contributes a methodology for modelling and simulating different performance criteria, which could be replicated in other climate contexts. Moreover, the implications drawn from this thesis pave the way for future studies on the passive solar design in hot-arid regions, and thus, this thesis serves as a future reference for both educational and research studies.
|Date of Award
|12 Oct 2022
|Tristan Kershaw (Supervisor) & Paul Shepherd (Supervisor)
- Outdoor Thermal Comfort
- Energy Consumption
- Urban Geometry
- Urban Typologies
- Courtyard Blocks
- Multi-objective Optimisation