Investigation into the daylight performance of expanded-metal shading through parametric design and multi-objective optimisation in Japan

Abstract

This paper presents a parametric and Multi-Objective Optimisation approach to investigate daylight performance of the expanded-metal shading depicting the sky conditions in Kitakyushu, Japan. The study is an initial design method utilising a robust computational calculation aiming to verify expanded metal as an environmentally friendly building material concerning its function as a shading device. The proposed platform generatively iterates the logic of expanded metal as dynamic design variables, such as Bond, Strand, Length, Height and Angle, to achieve the optimisation goals of minimising Annual Sunlight Exposure (ASE) while simultaneously maximising Spatial Daylight Autonomy, Useful Daylight Illuminance (UDI) and the openness of the expanded-metal profile. Ladybug and Honeybee were utilised in a parametric platform, Grasshopper, to perform daylight simulation, while Octopus was employed to optimise the results. A thorough analysis was conducted to determine the significance of each expanded-metal parameter in achieving the daylight and View objectives. The results showed that adopting the proposed framework successfully fulfilled the LEED v4.1 daylight requirements by reducing ASE by 100% and improving UDI by approximately 50% over the baseline model. Furthermore, the iteration process revealed a wide range of aesthetic patterns, providing another factor for designers to consider during the design decision-making process.