Computational Design Optimisation of the Thermal Performance of an Opaque Ventilated Façade in Hot Desert Climate Based on Biomimetic Inspiration

Abstract

This research investigated opaque ventilated façades, which have been proven to reduce heat transfer through the building envelope. Although their effectiveness in different climates has been evaluated by numerous studies, there is a notable lack of research on their application in a hot desert climate, and there are currently no computationally optimised designs for such façades in the current state of the art or studies on the biomimetic opaque ventilated façades. As a result, this thesis presents a comprehensive investigation into the optimisation of opaque ventilated façades tailored for a hot desert climate, utilising biomimetic principles. The research begins with an extensive review of existing literature and precedent studies to establish a theoretical foundation encompassing biomimicry, opaque ventilated façade design, and computational design optimisation. Building upon this theoretical groundwork, a baseline opaque ventilated façade was developed specifically for hot desert climates, with a prototype constructed to explore influential design parameters affecting its performance. Through systematic exploration of design parameters, it was identified that increasing airflow velocity within the cavity and maximising the shaded area of the façade are critical in reducing inner skin surface temperature, presenting significant technical challenges. The study then investigated biological solutions, drawing inspiration from rodent burrows and barrel cactus characteristics, to address these challenges. During concept and sensitivity analysis, rodent burrows and barrel cactus features were examined for their potential to increase airflow velocity, maximise façade shade, and reduce inner skin surface temperature. Twenty-four bio-inspired solutions are individually tested in the concept and sensitivity analysis phase, with computational fluid dynamics (CFD) simulations employed to evaluate their thermal performance. Among these solutions, two funnel-shaped louvres and the wide mound solutions exhibited superior performance in reducing inner skin surface temperature. The identified wide mound solution and the two funnel-shaped louvres solution undergo further refinement through parametric optimisation, utilising an advanced optimisation solver to generate a range of design options to determine the most effective configurations for reducing inner skin surface temperature and decreasing total surface area. Two options for wide mound and funnel-shaped designs were considered for reducing either inner skin surface temperature or minimising total surface area. Simulations show the larger wide mound solution as the best choice overall. Finally, this optimal design was applied to a three-floor commercial building in Riyadh, Saudi Arabia. The simulation results of this application demonstrated that this design can be successfully implemented in lowrise buildings with multiple floors in hot desert climates, lowering the façade surface temperature and enhancing thermal performance. In addition, the design application stage demonstrated that this optimal solution could be constructed similarly to other conventional opaque ventilated façades and could be customised to suit the architectural façade design of the majority of buildings. This research underscores the potential of biomimetic approaches to enhance the thermal performance of opaque ventilated façades in hot desert regions, offering a pathway towards sustainable building design solutions.