寒冷地区多层轻型木结构墙体热湿性能试验研究

Field study of the hygrothermal performance of multi-storey light wood-framed walls in cold zones

【目的】外墙是轻型木结构建筑的主要围护结构,其热湿性能对建筑耐久性、安全性、舒适性和能源消耗等均有较大影响。为探究室外环境、墙体朝向、楼层高度等因素对寒冷地区多层轻型木结构墙体热湿性能的影响,本研究对天津市某多层混合结构建筑中轻型木结构墙体的热湿性能进行了试验研究。【方法】2020年1月1日-2020年12月31日,对试验墙体内部环境温湿度、木骨柱含水率等热湿参数进行持续一年的监测,分析室外温湿度、墙体朝向和楼层高度等因素对墙体热湿性能的影响,评估墙体内部的冷凝风险和霉菌生长风险。【结果】墙体空腔内温湿度变化与室外温湿度变化趋势基本一致,木骨柱含水率变化与环境温湿度作用下的平衡含水率变化趋势基本一致,但墙体空腔内温湿度及木骨柱含水率的波幅小于室外环境。短期强降水引起墙体空腔内相对湿度和木骨柱含水率的增长,但增长过程具有一定滞后性。不同朝向墙体的太阳辐射强度不同,使其墙体空腔内温度分布规律为南向>西向>东向>北向,相对湿度分布规律则为北向>东向>西向>南向,木骨柱含水率分布规律为西向>北向>东向>南向,除西向外含水率与相对湿度分布规律基本一致。各楼层的温湿度分布规律明显,1层墙体内温度较低,相对湿度和木骨柱含水率整体偏高,且波幅较大;5-8月,墙体空腔内温度分布规律为4层> 3层> 2层,墙体空腔内相对湿度和木骨柱含水率分布规律为2层> 3层> 4层。【结论】墙体空腔内部温湿度和木骨柱含水率受室外环境条件的直接影响,但在室外环境大幅波动变化条件下,墙体内部处于相对稳定的热湿环境。寒冷气候区内,该多层轻型木结构墙体构造能有效阻隔室外水蒸气进入墙体内部,2020年气候条件下墙体空腔内部不存在冷凝和霉菌生长风险。

[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 multistorey 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.1 st to Dec. 31 st, 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 1 st 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 4 th floor was the highest, followed by that of the 3 rd and 2 nd floor.The relative humidity and moisture content in walls of the 2 nd floor were highest, followed by that of the 3 rd and 4 th 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.