A Modelling Study of Segmentation of Naturally Ventilated Tall Office Buildings in a Hot and Humid Climate

The prevailing paradigm in indoor environment control of office buildings often excludes natural ventilation, due to the fact that its dynamic nature may not be compatible with the close control of mechanical conditioning systems. Due to the potential magnitudes of wind and buoyancy forces in tall buildings, the challenges are greater. This research is concerned with the prospect of purely naturally ventilated tall office buildings. The naturally available driving forces of wind and buoyancy are investigated separately or in combination. For the present study, it is proposed that "segmentation" might offer the least risky approach for envelope design of non-residential tall buildings. Two modelling approaches are adopted for investigating the segmentation effects. Firstly, the single-cell envelope flow model is evaluated under the steady state condition. Further dynamic effect with the multi-cell model is then examined using dynamic thermal simulation with an airflow network using ESP-r (ESRU, 2002). Segmented and non-segmented atrium buildings with ventilated double façades are adopted as the main building configurations in the second stage for coping with the potential magnitude of impinging wind at high levels. The overall objectives are to determine whether the magnitudes of airflow rates and the desired flow pattern through openings can be achieved over a range of specified conditions. Potential conditions where the design goals may not be ensured are identified. It is supposed that a seasonal control algorithm could be developed to provide the optimum desired flow pattern, sufficient flow rates for ventilated cooling and uniform air flow rates across floors. The control of segmentation can be achieved by the use of dampers between cavities for the naturally ventilated tall office building design in the climatic context of Taipei, Taiwan.