On-site investigation and comprehensive performance testing analysis of building envelopes in existing residential buildings in Shanghai

Abstract

With the slowdown in economic and population growth, China's residential market is shifting from incremental competition to stock-based development, making the renovation and upgrading of existing residential buildings a new priority. As one of China's earliest cities to adopt industrialized housing, Shanghai boasts a vast and diverse stock of residential buildings, serving as an ideal case study for existing housing in China. This research focuses on the thermal performance of building envelopes in existing residential structures. Following an “investigation-testing-validation”methodology, field surveys covering 50+ communities were conducted, and four typical residential units were selected for comprehensive performance testing. Key influencing factors—the U-values of building envelopes and area ratios—were further analyzed through quantitative simulations. The main findings are as follows: The thermal performance of Shanghai's existing residential building envelopes fails to meet local and national energy efficiency standards, with roofs and exterior windows exhibiting the most significant deficiencies. Indoor temperature trends show a positive correlation with weighted U-values. For top-floor units, the roof U-values have the greatest impact on annual energy consumption, whereas for non-top-floor units, the exterior wall U-values are the dominant factor. The envelope-to-floor ratio influences indoor temperatures to a greater extent than the window-to-wall ratio. Larger envelope-to-floor ratios lead to more extreme indoor temperatures. Under typical conditions, changes in the envelope area ratio have a less pronounced impact than variations in the U-values of roofs and exterior walls. Based on these findings, the study proposes improvement recommendations for building envelopes at both the residential and policy levels.