Investigation of ventilation performance in the multi-story building with various envelope features: Scaled outdoor experiments

Previous research was limited to flat-façade buildings when evaluating the indoor and outdoor ventilation performance in a multi-story building. However, envelope features can provide the shading effect to induce the temperature difference between surfaces exposed to direct solar radiation and those without solar radiation. This temperature difference between surfaces can enhance the thermal buoyancy and change indoor and outdoor ventilation performance. We conducted scaled outdoor experiments to examine the impact of various envelope features on indoor and outdoor ventilation performance in multi-story buildings. Compared to the flat-façade multi-building, the average normalized horizontal airflow velocity of overhang, small wing wall, and large wing wall multi-buildings increased by 12.41%, 10.56%, and 5.56%, respectively. Cross-ventilation is more susceptible to envelope features than single-sided ventilation in air change per hour (ACH). Specifically, the ACH values of cross-ventilation for large wing wall, small wing wall, and balcony multi-buildings decreased by 69.98%, 25.79%, and 12.12% relative to the flat-façade building. For the same envelope feature building, the ACH values of single-sided ventilation on the windward side are better than those on the leeward side, particularly the building with small wing walls, with an improvement of 12.77% compared to flat-façade. This study contributes to advancing the understanding of urban ventilation, and provides a valid basis for designing envelope features in urban buildings.