Building Geometry and Operational Energy Performance: A Comparative Study of Residential Building Shapes in Esenyurt, Istanbul

Building geometry represents a fundamental design parameter that can substantially influence operational energy demand without requiring additional construction materials or advanced technologies. Optimizing building form may therefore provide a cost-effective, high-impact approach to improving thermal efficiency in affordable housing, particularly in climatic regions requiring both heating and cooling. This study investigates the influence of building geometry on the operational energy performance of affordable residential housing in Esenyurt, Istanbul, representing Türkiye’s mild-humid climatic region. It aims to determine how different residential building typologies influence annual heating, cooling, and overall energy consumption under comparable operating and climatic conditions. Architectural drawings of five representative residential building typologies, namely U-shaped, L-shaped, rectangular, H-shaped, and triangular buildings, were obtained from the Esenyurt Municipality and modelled using DesignBuilder with the EnergyPlus simulation engine. All simulation models employed identical material properties, occupancy schedules, HVAC operation, and climatic inputs so that the influence of building form could be examined under comparable operating conditions. Because representative real-world buildings were analysed rather than idealized prototypes, differences in building size were addressed by reporting energy performance as energy use intensity (kWh/m²/year). Simulations were performed using a 20-year hourly weather dataset obtained from the Turkish State Meteorological Service to capture long-term climatic conditions representative of Istanbul. The U-shaped building demonstrated the lowest overall annual energy use, at 174.65 kWh/m²·year, indicating an 11.8% decrease relative to the rectangular baseline. The superior performance of the U-shaped configuration is consistent with passive design principles that associate compact building forms and courtyard layouts with improved thermal performance under mild-humid climatic conditions. These characteristics collectively decreased heating loads by 9.5% and cooling loads by 17.6%. Conversely, the H-shaped and triangular configurations demonstrated the lowest levels of efficiency owing to high envelope exposure and insufficient shading, leading to increases of 8.3% and 14.5% in total energy consumption, respectively. The findings contribute to the growing body of knowledge on climate-responsive residential design by demonstrating how building geometry influences operational energy performance under standardized simulation conditions. Although the results are specific to Istanbul’s mild-humid climate and the selected residential typologies, they may assist architects, planners, and housing authorities in incorporating geometry-based passive design strategies into future affordable housing developments.