Fast design of buoyancy-driven ventilation openings for multi-story buildings with shared shaft using analytical solutions

Buoyancy-driven ventilation in multi-story buildings with shared shafts exhibits uneven effects across different stories. This study simplified Acred's dimensionless design approach into user-friendly analytical solutions to balance the uneven effects. When openings are designed using the proposed analytical solutions, each story achieves close thermal comfort temperatures. The influence of key parameters in the analytical solutions and three application constraints was analyzed. The results show that when the total number of stories N increases from 1 to 25, the average shaft enhancement parameter increases from 1.00 to 2.27. As the top-story shaft enhancement parameter ( E N , a design value) increases, the maximum total number of stories ( N max ) to which this method can be applied decreases sharply. Furthermore, near E N = 1.24, the governing constraint transitions from shaft roof area to critical area for bidirectional flow. The temperature gradient within the shaft leads to an approximately 11% deviation in practical performance.