This case study demonstrates how simulation-driven facade design can significantly improve indoor thermal comfort while reducing building energy demand. Using advanced modelling tools in DesignBuilder , the study evaluates how design parameters such as glazing, shading devices, orientation, insulation, and thermal mass influence occupant comfort and building performance. Through an iterative optimisation process, the project identifies facade strategies that balance daylight, solar heat gain, and ventilation to create more climate-responsive buildings. The analysis highlights the importance of passive design interventions, particularly external shading and appropriate glazing selection, in minimizing overheating and improving indoor comfort conditions without excessive reliance on mechanical cooling. By integrating performance simulation into early-stage design decision-making, the study showcases how architects and engineers can develop energy-efficient and occupant-centric buildings using data-driven methods.