Multi-objective optimisation of urban courtyard blocks in hot arid zones

Abstract

Courtyard blocks are well known for their tempering potential of the thermal conditions in various climates. In this paper, the building heights, orientation and interspaces of courtyard blocks are optimised for the hot-arid climate of Cairo, Egypt. Simulations are conducted using an evolutionary search algorithm within the Grasshopper parametric design environment for Rhino3D. The Ladybug-tools, plugins of Grasshopper were used to calculate the objective functions, the summer weekly cooling loads and the weekly average Universal Thermal Climate Index (UTCI). For three courtyard block types elongated 1, 2 and 3-fold the width of the inner court, the Pareto optimal sets of the three types all comprised solutions with the minimum interspaces. Orientation45° was predominant in the square type, whilst orientation135° was predominant in the elongated types (W/L = 2, 3). Using the weighted sum ranking, with the exception that orientation45° was preferred in the most elongated type, the optimal solutions reduced cooling loads by up to 31.7% and reduced UTCI by up to 1.6 °C, compared to a reference case. Solar radiation analysis showed that the optimised cases have great potential to increase the percentage of exposed surfaces by 4% to reduce the heating loads in winter.