Assessing Self-shading Benefits of Twisting Towers

Abstract

Over the last number of decades, tall building geometries have been shifting from rectangular boxes towards shapes that are defined through geometrical transformations such as twisting. While, from an aesthetical point of view, these twisting geometries make tall buildings appear contemporary and iconic, from an environmental point of view, however, the benefits are not as straightforward. They may vary significantly based on climatic loads and urban conditions, among others. This study aims to assess the self-shading benefits of twisting geometries by finding a correlation between floor-to-floor rotation and façade solar irradiation across climates, primarily focusing on hot ones, where self-shading is used as a passive solar design strategy. The study analysed three types of irradiation studies: Cumulative Annual Irradiation, Cumulative Harmful Irradiation during Cooling Design Day, and lastly, Solar Irradiation Self-Shading Balance. The latter compares beneficial and harmful solar irradiation during Hot and Cold Degree Days to quantify the impact of floor-to-floor rotation on optical and thermal performance. The study explored hundreds of possible scenarios across different climates and various floor-to-floor rotation angles, revealing a variety of positive, negative, and neutral situations. The study recommends careful examination of environmental conditions via a combination of multiple irradiation studies, particularly in the case of a smooth façade scenario.