Normalized roof garden renovation for carbon capture: conception, efficiency and application in urban regeneration

Abstract Within urban renewal contexts, population expansion, industrial upgrading, and infrastructural growth intensify climate vulnerability. Greening retrofits on high-density aging buildings can effectively reduce structural carbon emissions, mitigate urban heat island effects, and support community-level carbon neutrality goals. This study analyzes a representative residential roof garden retrofit employing spatial unitization of greening modules. By quantifying CO 2 capture capacity (T CO 2 ), structural mass (S green ), and roof load capacity (S d ), we evaluate carbon sequestration potential and efficiency (η CO 2 ) under constrained loading conditions. To ensure consistency in species composition and unit load, three representative plants, Jasminum nudiflorum, Chaenomeles speciosa, and Styphnolobium japonicum ‘Pendula’, were selected according to case-specific contextual criteria. Styphnolobium japonicum ‘Pendula’ demonstrated the highest predicted capture rate (10.83 g/m²/d), whereas Jasminum nudiflorum exhibited the lowest capture performance (2.13 g/m²/d). Both species showed comparable rooftop capture efficiency (η≈14%). Selecting high-efficiency species substantially improves system performance and informs optimized retrofit strategies. Moreover, the findings support roof garden renovation design, offering data references and management approaches for greening systems in urban renewal projects. This provides new insights for sustainable urban renewal and energy-conservation initiatives in developing countries.