On the Optimisation of Urban form Design, Energy Consumption and Outdoor Thermal Comfort Using a Parametric Workflow in a Hot Arid Zone

Yasser Ibrahim,David Coley,Tristan Kershaw,Paul Shepherd

doi:10.3390/en14134026

Abstract

The recent reports from the Intergovernmental Panel on Climate Change (IPCC) urge for the reconceptualization of our design of the urban built environments. However, current efforts to integrate urban environmental assessment into practice in Egypt are proving insufficient. This paper utilises the Ladybug tools simulation plugins to investigate the impact of changing the morphological characteristics of three-block typologies (scattered, linear and courtyard) and their associated parameters to understand their multidimensional relationship with environmental conditions, outdoor thermal comfort and energy use intensity. This study based in Cairo, Egypt, considers 3430 hypothetical geometrical configurations comprising of a variety of design parameters and indicators. The results show a strong correlation between the design parameters and the combined performance of thermal comfort and energy consumption (R2 = 0.84), with urban density having the strongest impact on both thermal comfort and energy use (R2 = 0.7 and 0.95, respectively). The design parameters exhibited a consistent impact on the different typologies, albeit with varying magnitude. Compact and medium-density urban forms are shown to elicit the best overall performance, especially for ordinal orientations (e.g., ~45°) across all typologies. Compact high-density scattered forms are favoured when considering thermal comfort, while courtyards outperform other typologies when considering energy efficiency and overall performance.

Highlights

The global population is expected to grow to 9.7 billion by 2050, with ~70% of those people living in urban areas [1]
Densification of the built environment is often typified by narrower urban canyons with impervious construction materials, reduced vegetation, and increased pollution, leading to increased sensible heat storage, shifting longwave heat emission, entrapment of shortwave radiation within the street level, as well as hindering the potential for evaporative and convective cooling, creating an Urban Heat Island (UHI) [4]
A simulation approach for hypothetical case studies is applied in this study. This approach is appropriate in parametric studies aiming to support stakeholders in the planning stage, where the use of abstracted building typologies and standardised design parameters reduces the complexity of parametric combinations, the simulation of a higher number of case studies, whose results can be interpreted by designers

Summary

Introduction

The global population is expected to grow to 9.7 billion by 2050, with ~70% of those people living in urban areas [1]. One of the pioneering studies trying to understand this relationship was the work of March et al [10] who suggested six simplified urban patterns in the form of archetypal building forms to investigate how density and surface coverage affect daylighting. Ratti et al [12], by virtue of image processing of Digital Elevation Models (DEMs), analysed shadow density and daylight distribution along with sky view factors as indicators for the thermal performance of March and Martin’s archetypes. Both studies have acknowledged the courtyard design as appropriate for hot-arid climates. Oke proposed a simplified classification of urban climate zones based on the built form configuration, terrain roughness, aspect ratio and ground imperviousness [13], which was further developed into 17 Local

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Conclusion