Moisture in clothing and its transient influence on human thermal responses through clothing microenvironment in cold environments in winter

Abstract

Air humidity produces conditions of varying moisture contents in clothing, which affects the heat and moisture transfer between human body, clothing and environment, as well as the wearers’ comfort. This study was designed to evaluate the moisture effects in clothing in cold environments. A series of wearing experiments were conducted in a climate chamber, simulating transient moisture absorption and desorption in experimental clothes. Totally 20 subjects were involved in three temperature levels (16 °C/20 °C/24 °C) and two relative humidity levels (15% RH/85% RH) during winter, with physiological measurement and subjective evaluation. The results showed that moisture in clothing under 85% RH significantly reduced subject mean skin temperatures (MST) and increased the local blood flow, due to enhanced heat loss by vapour evaporation. The initial skin wettedness was approximately 0.7 at 85% RH and stabilised at 0.33 after 90min exposure. The skin heat loss (Qskin) at 85% RH was almost twice as high as that at 15% RH under the same temperature conditions, owing to larger sensible and evaporative heat loss caused by moist clothing. The inner clothing effective temperature Teff was proposed to relate to TSV that the TSV increased by 1.12 units with an increase of 1 °C of Teff, which quantified the coupled effects of air temperature and humidity in clothing microenvironment on human thermal comfort. The findings address the negative effect of clothing absorbing a large amount of moisture, which should be considered for indoor heating temperature designs in cold-humid environments.