Effects of building interference on natural ventilation for high-rise residential buildings

Abstract

Natural Ventilation is widely acknowledged because it is able to improve the indoor environment, reduce the occurrence of sick building syndrome and save mechanical energy consumption, etc. It is a common ventilation mode in rural areas and developing countries. Yet, in urban areas, increasing number of compactly placed high-rise buildings greatly modifies the prevalent wind. Influences from nearby buildings then become significant. Readily available studies regarding the building interference effects on natural ventilation are limited, most of them focused on the civil and structural engineering disciplines instead. This study was performed to explore the relationship between natural ventilation and interferences from neighbouring buildings. A computational fluid dynamics (CFD) analysis was performed and the commonly adopted standard two-equation k-ε model (by commercial code FLUENT) was employed as the turbulence model. Sensitivities of wind direction, building separation and building configuration on natural ventilation were examined. Considering regularly placed buildings, relatively high ventilation rates were observed when the prevalent wind directions were in the range 15° to 30° inclined to the building centreline. Seven cases, with the building-separation- to-building-width ratio ranged from 1 to 7, were tested. Larger building separation substantially improves ventilation performances. The volumetric airflow rate is comparable to that of an isolated building when the separation is five times of the building width. Further increase in building separation is unable to promote the ventilation rate higher. A shift in the locations of alternate rows of buildings was found to promote the ventilation performance to a large extent. For each of the seven building-separation-to-building-width ratios, five cases of building shift were examined. The required ratio for approaching the ventilation performance of an isolated building is significantly reduced. A slight shift in building locations can therefore effectively improve the natural ventilation performance in densely built environment.