Energy consumption optimization in buildings, particularly in hot and dry climates, is a key approach to achieving sustainable architecture. This study aims to quantitatively evaluate the impact of passive design strategies on reducing energy use in the welfare service complex of the University of Kashan. The research method is based on modeling and simulating the building’s energy performance using DesignBuilder software and the EnergyPlus calculation engine. Several parameters were examined, including the initial building form, plinth height, window frame and glazing types, shading device dimensions based on Iran's National Building Regulations (Part 19), and the thermal material properties of exterior/interior walls and roofs. Input data included local EPW climatic conditions, material thermal transmittances, and space occupancy patterns, with annual energy performance simulated in terms of kWh/m².year. The quantitative results indicated that among the initial geometrical configurations, the square form exhibited the optimum performance with an energy consumption of 267.22 kWh/m².year. Furthermore, the integration of combined horizontal and vertical shading devices with a 100 cm depth achieved a significant cooling load reduction, lowering the consumption to 189.75 kWh/m².year. Regarding the building envelope, incorporating light-colored stone with glass wool insulation in exterior walls and a cool white reflective coating on the roof improved thermal performance by 9.91% and 8.27%, respectively. Ultimately, the concurrent implementation of these passive strategies successfully decreased the annual energy demand from the initial 267.22 kWh/m².year to the optimized 167.81 kWh/m².year, resulting in an overall 37.20% reduction. These findings highlight the vital role of climate-responsive principles in enhancing the energy efficiency of institutional buildings in arid zones.