A meter-level resolution least-cost-path method for fast urban ventilation assessment: Preliminary validation using CFD and wind tunnel

Fast urban ventilation assessment remains challenging in dense cities, where existing permeability-based morphometric methods cannot resolve three-dimensional airflow connectivity at meter-level resolution. In Hong Kong, this limitation is reflected in the Sustainable Building Design (SBD) Guidelines (APP-152), which rely on simplified geometric parameters that that are section-based and become cumbersome to compute for complex urban morphologies. This study develops a novel Least Cost Path (LCP) method for fast, spatially-explicit, and permeability-consistent evaluation of path-specific ventilation performance at meter-level resolution. The method models wind transport through three-dimensional urban forms as a set of inflow-aligned transport paths, in which path cost reflects cumulative resistance induced by frictional blockage and directional turning. Validation against Computational Fluid Dynamics (CFD) and wind tunnel modeling was conducted using both random building blocks and actual high-density urban neighborhoods in Hong Kong. Qualitative agreement is observed between LCP path distribution maps and wind velocity ratio ( VR ) contours, while quantitative analysis shows strong correlations with modeling results (R² = 0.85 for spatially averaged VR ; R² = 0.90 for bin-based, path-specific VR ). The method performs consistently across spatial scales and elevations, with slightly reduced accuracy in areas of highly heterogeneous building heights and leeward compact zones where vertical mixing and turbulence are not explicitly captured. Compared with CFD, LCP predictions reduce computation time for a typical urban redevelopment from hours to minutes on a standard computer. Implemented under an industry open standard for BIM, the tool is practitioner-friendly, enabling rapid learning and effective integration into architectural design practice.