Comparison of Horizontal and Vertical Natural Ventilation Strategies in Urban Townhouses

This research proposes horizontal and vertical natural ventilation strategies for upper-floor bedrooms of typical townhouse buildings, aiming to solve problems caused by single-sided ventilation and wind obstruction from adjacent buildings in housing development projects. A comparative study of ventilation performance was conducted for various building scenarios using Computational Fluid Dynamics (CFD) simulation under four design-strategy variables, two wind directions, two different street widths, and two townhouse layout types, totaling 32 cases. The results show that the bedrooms of typical townhouses have very low air movement through the average indoor air velocity coefficient (Cvi = 0.01–0.03) and very low airflow rate through the product of air velocity coefficient at openings and inlet area (Cvo × A = 0.01–0.04) values, especially in second-floor bedrooms with single-sided ventilation. Vertical and horizontal ventilation strategies can slightly increase the Cvi, while significantly improving the Cvo × A values, enabling indoor air quality to meet the required ventilation criteria. The one-way wind catcher provides the highest values in Cvo × A (0.08–0.13), followed by the two-way wind catcher (Cvo × A = 0.04–0.13), and then the horizontal ventilation strategy (Cvo × A = 0.04–0.11). From comparing the influence of the four variables on the ventilation performance of townhouses, the design-strategy variable has the greatest impact on increasing Cvi and Cvo × A values, followed by wind direction, and then street width and layout type, which have similar levels of influence. The findings ultimately give a comprehensive set of guidelines for townhouse design in urban conditions.