Integrating Sustainability and Age-Friendliness: A Pathway for Coordinated Renewal in Dense Urban Communities—A Case Study of Yuexiu, Guangzhou

High-density cities face dual challenges of aging populations and climate change, driving widespread renewal of aging residential communities. Current practices, however, often treat sustainability goals (e.g., energy efficiency, carbon reduction) and age-friendly design objectives (e.g., accessibility, social inclusion), often guided by frameworks like the World Health Organization’s (WHO) age-friendly cities initiative, as separate or conflicting agendas, leading to fragmented policies and suboptimal outcomes. This study addresses this gap by proposing and testing a framework for “Sustainable-Age-friendly Coordinated Renewal” (SACR). Through a mixed-methods case study of a typical old community in the humid subtropical city of Guangzhou, China, we investigate how green infrastructure and low-carbon interventions can be synergistically designed to enhance both environmental performance and the well-being of elderly residents. A “Coordinated Renewal Strategy Package” was developed, incorporating ecological shading, sponge city facilities, energy retrofits, and accessible slow-traffic systems. Post-intervention simulation and evaluation indicated significant improvements in microclimate (e.g., reduced mean radiant temperature and Physiological Equivalent Temperature (PET)) and marked increases in outdoor activity duration and social interaction frequency among elderly residents. This study concludes that a human-centric, needs-based design approach is key to unlocking synergistic benefits. The proposed SACR framework and evaluation matrix offer a practical tool for urban planners, architects, and policymakers to holistically assess and implement community renewal projects, contributing to more resilient, inclusive, and sustainable urban futures by addressing localized challenges like the Urban Heat Island (UHI) effect.