Thermal, energy and daylight performance of office buildings with balconies in subtropical climate

The use of balconies in tropical climates holds the potential to block direct solar radiation, thereby reducing energy consumption for cooling and enhancing visual comfort. However, balconies may also diminish daylight availability within the room, affecting occupants’ satisfaction and well-being. From abuilding performance perspective, balcony design is not always trivial and can affect building performance in multiple domains. The complexity in trade-offs of balcony design is evident in the literature, as scientific papers have scarcely explored the effects of the use of balconies on the building performance considering a multi-objective approach. Therefore, the main objective of this thesis was to provide balcony design recommendations to improve daylight, thermal, and energy performance of mixed-mode office buildings. A reference model representing a high-rise mixed-mode office building and possible variations of geometric parameters of balconies were defined based on a database of office buildings located in the city of São Paulo, Brazil. A parametric analysis was used to evaluate the effects of balcony and building design parameters on the reference model’s performance. A multi-objective assessment was performed through building performance simulations (BPS) for daylight, thermal and energy performance, using reliable software tools to assess different balcony design scenarios. To improve accuracy, computer fluid dynamics (CFD) simulations validated with wind tunnel experiments were used to generate wind pressure coefficient data, and daylight experiments were developed to validate the daylight simulations. The trade-offs of balcony design were assessed for daylight availability and visual comfort, as well as for natural ventilation, thermal and energy performance. The results were cross-analysed for daylight, thermal, and energy performance and recommendations for balcony design were tailored to each façade orientation and thoughtfully combined with the glazed door width. An optimal combination, featuring a 3-meter-wide glazed door and a 2-meter-deep balcony, proved beneficial for all façade orientations across all floor levels. However, the choice of parapet type should align with the balcony's location, which is directly correlated with the room's depth. This balcony design combination ensures optimal levels of daylight availability and improves visual comfort by up to 14%, enhancing thermal and energy performance within the room by up to 40%. The results of this research study pioneer in providing balcony design recommendations and offer valuable information for building designers, highlighting that balconies should not be designed solely as decorative façade elements or spaces for building services. Additionally, the methods developed in this research can be applied by researchers/designers to their own case studies.