Rethinking the Smartness of Cities: Microclimatic Performance of Public-Private Transition Spaces in Dense residential Areas of Tokyo

Urbanization and climate change demand new forms of urban resilience to promote livable environments. Many cities respond with Smart-City strategies that prioritize digital efficiency and data-driven optimization. Even citizen-oriented approaches remain largely technology-mediated, overlooking the ecological potentials embedded in daily life and underestimating how directly residents contribute to environmental performance. This research highlights Public–Private Transition Spaces (PPTS) in low-rise high-density residential areas of Tokyo as a human-centered alternative. Situated between private homes and the public street, these small spaces emerge through everyday actions of residents, such as positioning plants, objects and various boundary elements. Together, these practices and the material elements produce spatial forms that foster ecological performance as well as social interaction. A case study combining detailed mapping of PPTS and their components with surface-temperature measurements under humid subtropical conditions reveals measurable cooling effects. These findings show that simple practices by residents can generate tangible ecological benefits without relying on digital tools. By demonstrating the ecological value of plants within PPTS, this research reframes everyday spatial production as a form of vernacular climate practice. The study thus expands Smart-City discourses from standardized and technology-oriented solutions toward a human-centered, bottom-up urbanism and supports planning strategies that recognize small everyday spaces as vital components of livable urban environments.