The building sector accounts for a substantial share of global energy demand and greenhouse gas emissions, with space conditioning dominating operational loads. In Iran—a nation spanning five Köppen-Geiger climate zones—designing energy-efficient envelopes that simultaneously ensure occupant comfort remains a formidable challenge. This thesis introduces a reproducible, simulation-based multi-objective optimization (MOO) framework for the climate-responsive integration of Phase Change Materials (PCMs) in office buildings. The workflow couples EnergyPlus with the bespoke ChameleonPCM plugin (seamlessly embedded in Rhino/Grasshopper via Honeybee/Ladybug) and the NSGA-II genetic algorithm. Four decision variables—PCM type, melting temperature, layer thickness, and envelope placement—are optimized to minimize annual Energy Use Intensity (EUI) while maximizing Thermal Comfort Percentage (TCP), defined per ASHRAE Standard 55 adaptive criteria.