Managing and reducing energy consumption in residential buildings located in hot–dry climates is a fundamental requirement for sustainable urban development.This study aims to evaluate and optimize the energy performance of the building envelope by modifying its materials and physical components.A typical residential building in District 4 of Isfahan was selected as a representative case of prevailing construction practices.Thermal modeling and building energy simulations were conducted using specialized simulation software.To accurately assess the energy-saving potential, reductions in energy consumption were classified into two categories: methodological reductions and reductions resulting from physical envelope interventions. The results indicated that refining the model’s thermal zoning by realistically representing common and occupied spaces reduced the calculated annual energy use intensity from 137.45 to 104.50 kWh/m²·year, corresponding to a 23.97% methodological reduction. Subsequently, the implementation of envelope optimization scenarios—including intermediate insulation of external walls, the application of a reflective cool roof, lightweight internal walls, and triple-glazed windows—further reduced annual energy use intensity to 96.64 kWh/m²·year, representing an actual reduction of 7.52% relative to the revised baseline model. Moreover, integrating the optimized envelope with active solar systems—namely, photovoltaic panels installed at an optimal tilt angle of 38° and a solar water-heating system—reduced the final annual energy use intensity to 90.80 and 85.10 kWh/m²·year, respectively. Ultimately, the optimized model achieved Energy Class B in accordance with the requirements of Part 19 of the Iranian National Building Regulations. The findings provide prioritized passive envelope design strategies and active solar solutions for developing low-energy residential building models in hot–dry climates.