Windcatcher-driven air exchange optimization in an underventilated classroom: A coupled indoor–outdoor VLES study

• A novel simulation method reduces computational duration by at least eight times, with only a 13 % discrepancy from the experimentally determined air change rate. • All windows need to be open to achieve the recommended air change rate in a classroom with single-sided ventilation strategy. • Implementing a cross-ventilation strategy with only one window and a door open results in an air change rate that exceeds the required level by 15 %. • With the integration of a windcatcher, an opening to floor area ratio of merely 1.6 % enables achieving the recommended air changes per hour within a classroom. Natural ventilation plays a crucial role in sustaining indoor air quality within educational establishments in the province of Quebec, Canada, where at least 50 % of schools lack mechanical ventilation systems. This study conducts an experimental and numerical analysis to examine the efficiency of natural ventilation within a particular classroom during the winter season. The investigated classroom relies on single-sided ventilation in a wind-shaded area, thus limiting air exchange. During the cold season, at least one window should remain open to ensure air exchange, according to the governing authorities, despite a possible thermal discomfort due to incoming cold air. The present experimental and numerical results show that this ventilation scenario yields an underventilated classroom by 70 % in reference to the national building code’s requirement. Adding a windcatcher onto the building and connecting it directly to the studied classroom, while accounting for wind direction and shading effect, is achieved with a novel computational approach employing a localized pressure method within a Very Large Eddy simulation. This methodology enables simultaneous simulation of indoor airflow within the entire building interior and the surrounding environment. The total numerical domain encompasses a surface area of 143,040 m 2 and a volume of 8,582,400 m 3 . Notably, this is achieved while sustaining computational efficiency, requiring merely 72 h of computation time on a single 12-core computer. Findings indicate that adding a windcatcher yields up to a 1756 % and 659 % air change rate increase when comparing with one and two open windows (no windcatcher), respectively. The incorporation of a windcatcher reduces the need for frequent window adjustments and facilitates compliance with, and even exceeds, the air change rate mandated by national building codes. Renewing the classroom air is thus possible during a short recess with the door closed, ensuring exhaustion (no recirculation) of the accumulated CO 2 and other indoor contaminants and viruses.