Energy–Carbon Trade-Offs of Windcatcher Integration in a High-Thermal-Mass Courtyard House: A Combined EnergyPlus and CFD-Based Assessment in a Hot–Arid Climate

Traditional windcatchers are often discussed as passive cooling devices for hot–arid climates, yet their sustainability performance under contemporary comfort-controlled operation remains insufficiently understood. This study evaluates the energy and load-based carbon implications of integrating a windcatcher into a high-thermal-mass courtyard house in Şanlıurfa, Türkiye. A combined DesignBuilder v6.1/EnergyPlus v8.2 and CFD-based assessment was used: annual heating and cooling loads were calculated through EnergyPlus-based building energy simulation, while CFD analyses were used to interpret representative airflow behavior and localized thermal effects within the semi-open iwan. Scenarios varied operational schedule, geometry, material configuration, ventilation openings, and water pool integration. The results show strongly context-dependent performance rather than uniform energy or carbon benefit. Continuous operation weakened annual performance, whereas seasonal operation produced more balanced outcomes. The P.1 configuration produced the lowest total annual energy demand among the tested scenarios, decreasing total demand from 70,929.99 to 70,806.65 kWh/a, corresponding to a reduction of 123.34 kWh/a or 0.17% relative to the baseline. However, this limited reduction was accompanied by a 6.02% increase in cooling demand and a 2.52% decrease in heating demand. Consequently, the total load-based carbon indicator increased from 18.32 to 18.60 tCO2/year, corresponding to an increase of 0.28 tCO2/year or 1.53%. CFD results indicate that the semi-open iwan geometry and its orientation relative to prevailing winds constrained airflow effectiveness and limited the transfer of local cooling effects to conditioned zones. This study demonstrates that vernacular passive systems should be evaluated through integrated annual energy, airflow, and load-based carbon analyses before being adopted in sustainable renovation or climate-responsive design.