Effect of connection methods on hygrothermal performance of prefabricated concrete building walls

With the ongoing surge in global energy demand and the escalating environmental concerns, attention has turned to building energy consumption in numerous countries. According to a 2019 report by the International Energy Agency (IEA), the global building industry is responsible for 36% of energy consumption, ranking first among all industries. The 2022 China Building Energy Consumption and Carbon Emissions Research Report highlighted that in 2020, China's building energy consumption and carbon emissions represented 45.5% and 50.9% of the national total, respectively. Achieving carbon neutrality now hinges on decarbonizing buildings. Prefabricated buildings, as a prime example of industrialized construction, aid in reducing carbon emissions through standardized, factory-based production. However, unlike conventional construction, prefabricated concrete buildings (the dominant form of prefabricated buildings) employ metal connectors to join the prefabricated components. These metal connectors create thermal bridges that can influence heat and moisture transfer through the walls. In this study, a coupled heat and moisture transfer model will be established to analyze the influence of different connection methods on the hygrothermal performance in prefabricated concrete building envelopes. Two typical connection methods for prefabricated buildings are mainly investigated: the grouted sleeve connection and the bolted connection. The findings indicate that different connection methods for prefabricated building connectors increase both the heat and moisture transfer rates in prefabricated concrete structures. Compared to the grouted sleeve connection method, the bolt connection method has a more significant impact on the thermal and moisture performance of the wall. In the tests on the T-shaped structure, the grouted sleeve connections increase heat transfer by 9%-10%, while the bolt connections increase it by 52%-55%. During summer, the bolt connections show a 7.42% higher moisture transfer than the grouted sleeve connections, whereas, in winter, the bolt connections reduce moisture transfer by 12.4% more than the grouted sleeve connections.