Impact of Moisture Migration on Heat Transfer Performance at Vertical Joints of ‘One-Line’ Sandwich Insulation Composite Exterior Walls

Due to moisture migration effects, thermal and moisture bridges tend to form at building joints, thereby increasing the thermal conductivity coefficient of construction materials. To examine the influence of moisture transfer on the thermal performance of ‘one-line’ vertical joint walls, this study establishes a thermal–humidity coupling numerical model at the vertical joint of sandwich insulation composite walls. This model is employed to analyze the effects of various joint filling materials (aerated blocks, glass wool, concrete), insulation layer thicknesses, and environmental conditions on the thermal transfer properties of the wall joint. The results indicate that when filled with aerated blocks, the joint is most significantly affected by moisture transfer, exhibiting a heat flow loss rate of 8.08%. In high-temperature environments, the thermal transfer performance at the connection of the composite wall is particularly susceptible to humidity, with heat flow loss rates ranging from 6.17% to 8.74%. Furthermore, an increase in the thickness of the insulation layer leads to a reduction in the “heterogeneity” of the sandwich insulation wall, which reduces the wall’s effects to moisture transfer; however, this is accompanied by a rise in the heat loss rate at the connection. After accounting for the effects of hygrothermal bridging, the mean heat transfer corrected coefficient of the wall in areas with hot summers and cold winters ranges from 1.10 to 1.18 during the summer and from 1.12 to 1.16 during the winter. This finding holds significant relevance for aiding researchers in predicting thermal transfer analysis in scenarios involving wall moisture transfer.