Evaluation of ventilation performance of monitor roof in residential area based on simplified estimation and CFD analysis

Wind-induced natural ventilation is beneficial to assure thermal comfort and to reduce cooling load in the hot and humid summertime. In the urban environment, where buildings are grouped closely, it is often difficult to obtain a large enough wind pressure difference to drive the natural ventilation. As architectural feature, this work focuses on “monitor roof” which has the potential to promote wind-induced natural ventilation, and aims to evaluate its ventilation performance. This paper analyses a two-story residential building model equipped with a monitor roof which is built in a long building row, assuming a densely populated residential area. Since the monitor roof shows complicated flow resistance, the conventional method to predict flow rate cannot be easily applied. Based on the correlation between internal pressure and flow rate, and wind pressure coefficients obtained from previous work, a simplified estimation method of flow rate is first applied in this paper. In addition, more detailed flow characteristics inside the room are analysed by Computational Fluid Dynamics using a Reynolds-Averaged Navier–Stokes model, and a certain level of accuracy is verified by comparison with wind tunnel measurement. By comparing flow rate between numerical simulation and measurement, the validity of the simplified estimation method is also verified. To analyse substantial ventilation performance including the effect of turbulence, numerical simulation using Large Eddy Simulation is also performed and particle tracking technique is applied. Based on those results, Purging Flow Rate is evaluated, and it is finally shown that the monitor roof can work well to promote natural ventilation.