Optimization of External Horizontal Slat Configurations for Enhanced Tropical Daylighting in High-Rise Apartments

Tropical regions experience intense and highly variable solar radiation, often resulting in excessive indoor illuminance, uneven daylight distribution, and visual discomfort in high-rise residential buildings. This study investigates the daylighting performance of various external horizontal slat configurations as a shading strategy for east- and south-facing rooms in a typical high-rise apartment under both intermediate sky with sun and overcast sky conditions. Using IESVE simulations, ten shading device (SD) configurations (SD 1–SD 10) were evaluated for their impact on daylight illuminance and distribution uniformity. Results show that high-rise apartment room with a commonly used overhang provided poor daylighting quality, with excessive illuminance and low distribution uniformity. SD 10 and SD 9 achieved the best performance at 09:00 and 12:00, respectively, for east-facing rooms across design days, while SD 10 was optimal for south-facing rooms on both 21 March and 22 December. Under overcast sky conditions, SD 9 demonstrated superior performance. This study proposes a novel adaptive external shading device featuring adjustable horizontal slats that can be reconfigured throughout the day to respond to changing solar positions and sky conditions. This approach overcomes the limitations of fixed shading systems by adapting to dynamic tropical sky conditions, offering a practical solution for enhancing daylight quality in tropical high-rise apartments. The findings provide design guidance for the development of energy-efficient shading, climate-responsive shading systems tailored to tropical environments.