Building renovations in climates characterized by a hot summer and cold winter (HSWC) pose significant challenges in managing carbon emissions due to increased energy demands and material use. Despite advances in sustainable design, the carbon footprint of renovation activities remains a critical concern, particularly regarding the balance between initial emissions from construction and long-term operational efficiency. This study addresses these pressing issues through analyzing the carbon emissions associated with a building complex renovation in an HSWC zone of China. The research examines both the construction stage, where material production and transportation contribute significantly to emissions, and the operational stage, where energy consumption and equipment degradation influence long-term carbon output. By evaluating the effectiveness of renovation strategies and integrating building-integrated photovoltaic systems, this study demonstrates a reduction in annual carbon emissions from 1176.28 tCO2 to 1007.25 tCO2, a reduction of approximately 14.4%. The findings showed that the renovation process would achieve a carbon payback period of 7.46 years and a 24.9%–37.8% reduction in carbon emission intensity. This work underscores the potential significant environmental benefits of innovative materials and efficient design, offering valuable insights for future low-carbon building renovation projects.