Modified fabric jalousie as a dynamic external shading to improve daylight performance for tropical buildings

Dynamic shading systems are frequently used to regulate daylight and reduce visual discomfort in office buildings located in tropical climates. The majority of existing systems depend on high-carbon, heavyweight materials such as aluminum, and this material dependency restricts both environmental sustainability and design adaptability. Therefore, this study aimed to investigate the potential of a fabric-based modified jalousie system as a dynamic external shading strategy to improve daylight performance in tropical buildings by integrating computational simulations with full-scale field experiments. Daylighting simulations were performed for three fabric colors (light, mid-tone, and dark) with openness factors (OF) of 1, 3, and 7%, respectively. The process was followed by tilt-angle optimization applied through the Octopus evolutionary solver based on Useful Daylight Illuminance (UDI) and Spatial Daylight Autonomy (sDA) targets for morning, midday, as well as afternoon conditions. The two best-performing configurations, specifically light-colored and dark-colored fabrics with an OF of 7%, were selected for experimental validation. Field measurements showed that both configurations achieved illuminance uniformity (U) values above 0.4 and met the recommended minimum illuminance (E) level of 300 lx. The light-colored fabric provided superior daylight distribution under high solar irradiance, and the dark-colored fabric was more effective in mitigating glare. The result indicated that a fabric-based modified jalousie system effectively balanced daylight availability and visual comfort, offering a lightweight and sustainable alternative for dynamic external shading in tropical building applications.