External versus internal solar screen: Simulation analysis for optimal daylighting and energy savings in an office space

Abstract

Façade treatments have a significant impact on improving daylighting and energy performance. In desert climate, clear sunny sky is the prevailing condition which can be associated with excessive heat gain and non-uniformity in daylight distribution. This paper aims to identify the effect of two positions of a solar screen on daylighting efficiency and energy savings. First, simulation-based optimization was conducted to explore screen configurations that meet daylighting requirements for a generic south-oriented office in Cairo. Then, energy savings were quantified for the selected optimal cases to find the balance between daylighting and energy efficiency. Generative performative design approach was adopted, where solar screen patterns were generated using Cellular Automata (CA) as a generative system. Then, Genetic Algorithms (GAs) were integrated within the design process to optimize screen configurations regarding the IES metrics; spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE). Simulations were conducted using DIVA-for-Rhino and the parametric tool Grasshopper to automate the optimization process. Results demonstrated that the assigned daylighting criteria were met in both cases whereas, the external solar screen was more effective in decreasing energy loads which reached about 85% less than the internal.