Balcony design to improve natural ventilation and energy performance in high-rise mixed-mode office buildings

Balconies have the potential to promote airflow and regulate solar heat gain, which can reduce energy usage for cooling in buildings. However, designing these elements can be challenging due to complex trade-offs for natural ventilation and energy performance, highlighting the need for advanced simulation tools to guide balcony design decisions. This study aims to evaluate the impacts of balcony design on natural ventilation and thermal and energy performance in high-rise mixed-mode office buildings in São Paulo, Brazil. To this end, an integrated method that involves computational fluid dynamics (CFD) and building performance simulations (BPS) is developed to identify optimal solutions. Through this method, the performance of 40 balcony designs is studied, comprising diverse alternatives for three balcony design parameters (width, depth, and location on the façade). Furthermore, the research is performed considering the balcony effects on two façade orientations (north and south), two wind incidences (windward and leeward), and three floor levels (upper, medium, and lower floors). Results are analysed through a sensitivity analysis, percentage of change and cross-analysis. The findings indicate that narrow and shallow balconies (2 m × 0.5 m) are the best design option for the south façade; they enhance natural ventilation and reduce energy consumption for cooling across all floor levels and balcony locations. Conversely, for the north, sun-facing façade, it is recommended to use wide and deep balconies (5 m × 2 m) to reduce solar gains and associated energy consumption for cooling, despite potential limitations in natural ventilation.