Daylight Optimisation for Visual Comfort in High-rise Offices Using External Light Shelves in Tropical Climate

Excessive and unpredictable external illuminance in tropical climates often leads to challenges for indoor lighting, including in office buildings, causing user dissatisfaction due to light non-uniformity and glare discomfort. This study explores optimal external shading design with light shelves to enhance daylight quality and quantity in Malaysia's tropical high-rise, deep-plan office building. Utilising a base model and radiance engine for simulations in Integrated Environmental Solutions-Virtual Environment (IES-VE) software, eighteen configurations of flat light shelves were tested under controlled conditions. Metrics such as daylight factor (DF), work plane illumination (WPI), and WPI ratio distribution were utilised to analyse both quantitative and qualitative performance assessments. The light shelf configurations LS3B, LS3C, LS4A, LS4B, and LS4C achieved a daylight factor between 1.0% and 3.5% in more than 26.32% of the reference points, categorising them as having high potential for daylight utilisation. In contrast, the base case and several other configurations were classified as having low potential based on these criteria. The study concludes that external light shelves can significantly improve daylight quality and quantity in offices. The design strategy for light shelves, particularly LS4A, was identified as optimal, showing enhanced DF, WPI, and uniform WPI distribution across all orientations, achieving notable improvements in indoor daylight in accordance with set standards.