A new building ventilation assessment tool for high-density urban areas: integrating the least cost path method into building permeability parametrization

Evaluating building air ventilation performance is critical in Hong Kong’s densely populated, high-rise urban environments. Traditional methods, such as wind tunnel testing and Computational Fluid Dynamics (CFD) simulations, are often time-intensive and impractical during the early design stages. Geometric parametrization methods, including Frontal Area Density (FAD) and Permeability (P), offer simpler alternatives by quantifying porosity, but they fail to account for airflow dynamics shaped by building configurations.

This study proposes an innovative approach that integrates the Least Cost Path (LCP) method into building permeability parametrization for building ventilation assessment. By treating urban environments as porous media, the LCP method uses two cost-based metrics: Friction Cost (FC), representing airflow resistance, and Turning Cost (TC), reflecting path configuration complexities. These metrics are applied on a 3D grid system, aligning with the Hong Kong Sustainable Building Design Guidelines (APP152). The methodology employs CFD simulations to validate the LCP method across various random building configurations, ensuring robust comparisons with traditional CFD results.

Results demonstrate that the LCP-derived FC and TC metrics correlate strongly with CFD wind speed simulations (R² > 0.9). Moreover, scenarios meeting APP152 requirements consistently show higher ventilation efficiency, confirming the method’s alignment with current regulatory frameworks. The study also identifies threshold LCP costs that differentiate “good” from “poor” ventilation designs, providing actionable insights for architects and urban planners.

By enabling efficient, geometry-based evaluations of ventilation performance, the LCP method bridges the gap between early-stage design assessments and complex simulations. Its integration within Building Information Modeling (BIM) frameworks further enhances its applicability, offering a scalable, data-driven tool to improve building ventilation strategies in Hong Kong and similar high-density cities.