Enhancing natural ventilation, thermal comfort and energy savings in high-rise residential buildings in Bangkok through the use of ventilation shafts

Abstract This paper describes a computational fluid dynamics (CFD) analysis of the potential use of ventilation shafts in tall residential buildings in Bangkok to enhance natural ventilation and to improve thermal comfort (and thereby reduce air conditioning energy consumption). The study focused on a room with single-sided ventilation (i.e. openings in just one external wall). A ventilation shaft located at the rear of a room can raise the average air velocity across the room by greatly increasing the pressure difference between the room’s window and the shaft’s exhaust at roof level. A hypothetical room in a 25-storey residential building in Bangkok was devised to represent a typical residential unit in Bangkok. Air velocities in the predefined occupied areas of the room without and with a ventilation shaft (called reference and test room respectively) were assessed using the CFD package in the DesignBuilder modelling software, and the comfort hours during summer in both rooms were calculated based on the room’s operative temperature after they had been moderated by the elevated air velocities. Results indicate that average air velocities in the reference room were very low and insufficient to produce any cooling effect, regardless of external wind conditions, whereas air velocities in the test room were greatly enhanced compared to the reference room. Percentage comfort hours during the summer rose from 38% in the reference room to 56% in the test room, suggesting that approximately 2700 kWh of air conditioning energy savings could be achieved in the room by employing the proposed ventilation shaft.