Urban project-level analysis reveals green technologies decreased the carbon intensity of China’s building construction during 2012–2024

<h2>Summary</h2> Rapid growth of China's building stock intensifies material demand and construction-associated CO₂ emissions. However, existing studies have not sufficiently captured regional variation due to highly diverse construction technologies, building structures, and typologies across China. This study analyzes the patterns, drivers, and mitigation strategies of material consumption and associated CO₂ emissions using a dataset of 6,132 buildings in 228 of China's urban projects (25 million m²). We observe a consistent decline of 17.3%–20.3% in carbon intensity during 2012–2024, primarily attributable to low-carbon transitions in steel and concrete production. In mountainous areas, however, higher mortar use increased emissions by up to 10.6%, as seen in Chongqing. Scenario analysis shows that extending building lifespans, together with production-side decarbonization, can deliver substantial mitigation, reaching almost 1.5 billion tons (Bt) compared with the Shared Socioeconomic Pathway 1 (SSP1) baseline by 2060. The findings provide high-resolution insight to inform targeted low-carbon policies in China's construction sector.