Cross-ventilation of a generic building with various configurations of external and internal openings

Cross-ventilation is the most effective mode of wind-driven natural ventilation but completely depends on the external openings and internal layout. This study investigates how openings affect cross-ventilation of a generic four-wall space using Computational Fluid Dynamics (CFD) simulation. The building has one to four external openings of two different sizes, and the interior contains various configurations of vertical and horizontal walls with blockage ratios varying between 5% and 20%. Two-opening configurations proved to be tremendously efficient for cross-ventilation; for all similarly sized openings, the two-opening scenario doubles the ventilation rate of the single-opening scenario. Using a larger opening on the windward or leeward surface, the two-opening configuration achieved higher ventilation rates and better indoor wind circulation than both the three- and four-opening configurations. In turn, to enhance cross-ventilation in three- and four-opening configurations, more than one of the openings needs to be larger than the rest. The presence of internal walls always led to smaller ventilation rates than no internal walls; such reduction steadily increased with internal blockage ratio. The reduction in ventilation rates can be minimized by adopting several narrow internal walls instead of one wide vertical wall and positioning horizontally-oriented walls above the opening height.