Comparing daylight performance of dynamic and static shadings in office façades across multiple U.S. cities with various sky conditions

Shadings have a crucial role in daylight performance of buildings; however, their impact is dependent on both sky conditions and shading specifications. This study investigates the daylight performance of both dynamic shading systems and compares them with static shading at various rotation angles in a nearly fully glazed office unit. In addition to rotation angle, shading geometry and sky condition are examined to evaluate their combined impact on façade performance. The Hourly Useful Illuminance (HUI) metric is introduced to assess hourly illumination levels for three International Commission on Illumination sky types: sunny with sun, intermediate with sun, and cloudy. Simulations reveal that both dynamic and static shadings perform better under sunny skies than under intermediate ones, and both negatively affect daylight performance under cloudy conditions, with dynamic shadings showing greater superiority under sunny and intermediate skies. The superiority of dynamic shadings was greater in Las Vegas with a sunny sky; the difference of HUI between dynamic and static shadings is 4.5 for rectangular and 5.7 for triangular shadings. Rectangular geometries perform slightly better than triangular ones, though the difference is marginal. The study also determines optimum rotation angles for dynamic and static shadings and shows that as cloudiness increases, the range of effective rotation angles narrows. Additionally, analysis across multiple cities indicates that the decline in the useful illuminance level (HUI) at some time steps corresponds to changes in solar altitude and sky brightness, occurring around noon under sunny conditions and during midday and the summer season under intermediate skies.