Impact of the building envelope and orientation on thermal comfort and energy performance of residential buildings in tropical regions

Building envelope materials and orientation play a crucial role in enhancing natural ventilation, reducing energy demand, and improving thermal comfort in low-income tropical housing. This study evaluated the potential of passive building envelope strategies to enhance the thermal and energy performance of residential buildings in Kampala, Uganda. Specifically, it assessed the effects of optimized building orientation and envelope materials on indoor thermal conditions, occupant comfort, and energy-related heat gains. IES VE v2024 was employed to simulate and compare a residential building base model with an optimized test model, using metrics, such as air temperature, relative humidity, internal heat gains, and predicted percentage of dissatisfied (PPD). Simulation results were validated against on-site measurements. The optimized interventions reduced annual discomfort hours above 28 °C by 44.3% in the living room and 72.7% in the master bedroom. Indoor temperatures decreased from 0.5 to 1.0 °C, accompanied by improved humidity control. Internal heat gains were also reduced, including a 4.0% reduction in lighting gains and significant reductions in solar and external conduction gains. PPD decreased by 16% in the living room and 10.4% in the master bedroom. Validation demonstrated improved performance of the test model, including lower peak-hour relative humidity despite minor deviations between simulated and measured values. These findings indicate that climate-responsive orientation and envelope-material optimization can substantially improve thermal comfort and energy performance in tropical residential buildings. This study provides evidence to inform passive design guidance for energy-efficient housing in Uganda and supports SDGs 7, 11, 12, and 13 by reducing building energy demand and environmental impacts.