A building-scale modeling framework for urban net-zero transitions in Nanjing.

Carbon reduction during the operational phase of buildings is a critical component in achieving global carbon neutrality objectives. Current emission estimation methods often overlook building-level heterogeneity, limiting precise retrofit strategies. Here, we develop a building-based emissions accounting framework incorporating building typology, function, and geometry, augmented by facility-level power plant data. We propose tailored operational-phase mitigation technologies, analyzing 2020-2050 pathways through baseline, regulatory, and blueprint scenarios. Demand-side strategies target energy behavior modification (e.g., efficient lighting), while supply-side interventions prioritize coal-to-biomass conversion and fossil plant retirement. Applied to Nanjing (534,000 buildings across 101 streets), results show commercial buildings exhibit 3.9 times higher carbon intensity than residential units. End-use efficiency upgrades (HVAC, lighting, appliances) prove most effective for commercial sectors, whereas supply-side gains derive primarily from accelerated coal plant phaseout before 2045 and renewable integration (solar/wind/nuclear). This approach provides actionable building-specific decarbonization pathways, offering policymakers science-backed strategies for urban energy transitions.