A comparative study on the natural ventilation performance in buildings with different roof shapes

Abstract

The extensive use of mechanical ventilation systems is severely impacting the environment as these systems are one of the major sources of greenhouse gas emissions. Natural ventilation can effectively replace mechanical ventilation systems if the performance of the former is enhanced. The performance of a natural ventilation system depends on many factors such as the geometry of the building, opening size, shape, and positions. The studies related to quantitative analysis of natural ventilation performance in buildings are limited. Even though some of the studies have investigated the performance of natural ventilation in flat-roof buildings, however, completely ignore gable roof buildings. Considering the widespread usage of gable roof structures it is highly significant to investigate the natural ventilation performance in gable roof buildings.  Thus, in this work, the quantitative assessment of natural ventilation performance in gable roof buildings has been investigated and compared with the flat roof buildings using computational fluid dynamics (CFD). Six different configurations based on the relative locations of the windward and leeward openings were considered for both roof shapes. Numerical simulations were carried out using ANSYS-FLUENT software to investigate the ventilation performance for each of the configurations. The three parameters selected for evaluating the natural ventilation performance are normalized average velocity magnitude (V*), velocity homogeneity index, H, and normalized volumetric flow, Q*. The results showed that the flat roof configurations have higher values of V* and H which infers that flat roof configurations have better natural ventilation performance than gable roof configurations. Moreover, among the six configurations tested the configuration with windward opening below the mid-height and the leeward opening above the mid-height of the building wall has the best natural ventilation performance. The configuration with the windward opening at the mid-height and leeward opening below the mid-height of the building wall has the highest volume flow rate.