Configuration of horizontal voids and lightwell to improve natural ventilation in high-rise residential buildings in hot humid climate

Abstract

Cross-flow ventilation is the most effective strategy for providing thermal comfort and ensuring air quality in buildings, while minimizing the required energy cost. In hot and humid climate, the high-rise building plan configuration incorporates different types of lightwell, either in the core or perimeter of the building, that allow for opening the windows in different directions and thus enables better cross-ventilation. The lightwell space is subjected to produce a suction effect along its space and thus adjoining indoor spaces. Lightwell at the core with opening at top trapped unwanted gases and thus reduce the fresh air flow in its space and reduce the cross flow ventilation in adjoining units. Nevertheless, having a lightwell may not be enough to provide adequate natural ventilation in high rise buildings. This study examines the internal lightwell connection to the outside through different horizontal voids as inlets. A Computational Fluid Dynamics (CFD) technique employing ANSYS Fluent code is used to predict airflow characteristics for eighteen (18) alternative ventilation configurations of a full-scale building model. The full-scale model was developed according to common configurations of high-rise residential (HRR) buildings in Kuala Lumpur, as well as referring to the minimum requirements of the Malaysian Uniform Building By-Law (1984). The results show that the existence of a direct connection of the internal lightwell through a horizontal void affects the air change per hour (ACH) and the thermal comfort in the lightwell space and adjoining units, respectively. Although the existence of double-level voids increases ACH by up to 67 % along the lightwell, it reduces the air velocity by 70 % in adjoining units compared to the lightwell without direct connection. In order to reduce such contrast and to optimize the cross-flow ventilation in the lightwell and its adjoining units, the study recommends giving more attention to the lightwell inlet design. This study provides proper guidelines to predict ventilation performance and to improve the design of naturally ventilated HRR buildings.