Hybrid experimental – numerical evaluation of natural ventilation and courtyard microclimate for passive cooling in Mediterranean urban block

The accurate simulation of courtyard microclimates remains a critical challenge in evaluating passive cooling strategies in dense urban environments, particularly under variable window operation. This study investigates the combined effect of courtyard geometry and natural ventilation control on indoor thermal comfort in a Mediterranean urban block, using a hybrid experimental – numerical approach. A 1:10 scaled physical model of a courtyard building was constructed and monitored under summer conditions in northern Morocco, capturing indoor and courtyard air temperatures, surface temperatures, and meteorological data. A detailed multizone thermal and airflow model was developed using TRNSYS 18 coupled with CONTAM, incorporating bidirectional airflow modeling at window openings and radiative interactions based on Gebhart factors. Model validation against experimental measurements yielded high accuracy, with mean absolute errors below 1.5 °C and coefficients of determination (R²) exceeding 0.96 for both air and surface temperatures.Parametric simulations explored three courtyard configurations (W/L = 1.0, 0.67, 0.5), seven orientations (0°-90°), and four window control strategies (closed, open, night ventilation, conditional). Results indicate that night ventilation reduced cumulative indoor discomfort by up to 56% compared to sealed conditions, while compact courtyards improved ventilation and decreased UTCI by up to 3 °C during peak hours. Orientations aligned with prevailing winds (15-30°) significantly enhanced airflow rates. This study demonstrates the applicability of validated TRNSYS-CONTAM coupling for modeling courtyard-scale microclimates. The proposed methodology provides a replicable framework for assessing passive cooling efficiency through geometry - ventilation interactions in warm climate contexts.