Scattered coal consumption in the building sector contributes approximately 40% of China's primary fine particulate matter emissions and 10% of fossil fuel CO2 emissions, posing serious threats to climate change mitigation and air quality. Therefore, a shift from coal to natural gas (NG) and electricity is of great significance for the synergistic reduction of air pollutants and carbon emissions. However, the lack of building energy statistics at finer spatial scales makes it difficult to form targeted local strategies. In this study, a spatial downscaling framework was developed to project building energy consumption with higher resolution based on openly available information. Then, major air pollutant emission reductions induced by scattered coal substitution policies were estimated from national, provincial and city perspectives. The role played by buildings in realizing the overall carbon mitigation potential was also evaluated. The results show that a policy-driven increase in NG and electricity consumption during the 13th Five-Year Plan (FYP) period could contribute 15% and 4% to national SO2 and NOx emission control targets, respectively, and is helpful for some less-developed areas in achieving greater health benefits and faster low-carbon transformation. Finally, policy recommendations are proposed according to regional differences in emission reduction performance and socioeconomic development.