Objective  The exterior wall is the main enclosure structure of light wood-framed buildings. Its hygrothermal performance has a great impact on the durability, safety, comfort and energy consumption of buildings. In order to explore the influence of outdoor environment, wall orientation, floor height and other factors on the hygrothermal performance of multi-storey light wood-framed walls in cold zone, this study conducted an experimental study on the hygrothermal performance of light wood-framed walls in a multi-storey mixed structure building in Tianjin of northern China.

  Method  The study conducted a field monitoring investigation of multi-storey light wood-framed walls of a hybrid building in Tianjin from Jan. 1st to Dec. 31st, 2020. Temperature and relative humidity of the stud cavity in the test walls, moisture content of wood studs, et al were monitored continuously. The influences of outdoor temperature and humidity, wall orientation and floor height on hygrothermal performance of the wall were analyzed, and the condensation risk and mold growth risk inside the wall were assessed.

  Result  The trends of temperature and relative humidity of the stud cavity were approximately consistent with that of the outdoor environment. The trends of moisture content of wood studs were approximately consistent with the equilibrium moisture content of the stud cavity. While the amplitudes of the temperature and relative humidity of the stud cavity and the moisture content of wood studs were smaller than that of the outdoor environment. Relative humidity of the stud cavity and moisture content of wood studs increased with a time lag under heavy precipitation in a short term. Solar radiation on walls varied with orientations, resulting in the temperature difference. Temperature of the stud cavity in the southern wall was the highest, followed by that of the western, eastern and northern walls, while the distribution of relative humidity was opposite. The relative humidity of the stud cavity in the northern wall was the highest, followed by that of the eastern, western and southern wall. It was shown that the moisture content of wood studs in the western wall was the highest due to the high initial moisture content, followed by that of the northern, eastern and southern wall. Except for the western wall, the distribution of the moisture content of wood studs was roughly consistent with that of relative humidity. Relative humidity and moisture content of the stud cavity on the 1st floor were generally higher with larger amplitudes than the other floors. And its temperature was relatively lower. From May to August, the temperature of walls in the 4th floor was the highest, followed by that of the 3rd and 2nd floor. The relative humidity and moisture content in walls of the 2nd floor were highest, followed by that of the 3rd and 4th floor.

  Conclusion  Temperature and relative humidity of the stud cavity and moisture content of wood studs are directly affected by the outdoor climate conditions, while the hygrothermal conditions in the wall keep relatively stable. The outdoor vapor permeation is effectively retarded by the well-designed light wood-framed wall in cold zones. The cavities of multi-storey light wood-framed walls have no risk of condensation or mold growth in 2020.