Investigation of condensation behavior in self-insulating recycled concrete composite block walls

Condensation inside walls can lead to increased building energy consumption and mold growth inside the walls, which needs to be taken seriously. Current research on wall condensation mainly focuses on traditional homogeneous multi-layer slab walls. However, self-insulating block walls, a new form of thermal insulation wall, fill the holes of hollow blocks with insulation materials. The internal heat, moisture transfer, and condensation characteristics of these walls are still poorly understood. To evaluate the internal condensation of self-insulating recycled-concrete composite block walls in cold zones of China, meteorological parameters of Xi'an were selected as the calculation background. The heat and moisture transfer behavior within the self-insulating block walls was simulated using COMSOL Multiphysics software, considering both summer and winter separately. The condensation risk at different positions inside the walls was evaluated. Also, the influence of block hole arrangement on the condensation risk of walls was examined. The results indicate that, in both summer and winter, the location most prone to condensation in self-insulating block walls is at the first interface between the outdoor recycled concrete layer and the insulation material. As the number of hole columns increases, the risk of condensation inside the block wall decreases. As the number of hole rows increases, the risk of condensation increases. In summer, the condensation risk is lower when using a staggered arrangement of holes compared to a sequential arrangement, whereas in winter, the opposite is true. The findings can provide guidance for optimizing the design of self-insulating block walls.