Seasonal effect of humidity on human comfort in a hot summer/cold winter zone in China

Abstract

Adaptation to different seasonal climates may affect human subjective responses to humidity. In this study, thermal comfort, humidity comfort and perceived air quality were investigated with subjects exposed in a climate chamber during spring, summer and winter. Sixty subjects were recruited in total, divided into groups of 20 subjects for each season. Temperature was set at three levels (cool, moderate and warm) during experiments in ranges of 20–28°C, 23–32°C, 16–28°C for spring, summer and winter, respectively. Likewise, relative humidity was set at three levels: 15% (low), 50% (moderate) and 85% (high). Results showed that seasonal difference had a significant effect on human subjective responses to humidity. The combined effect of temperature and relative humidity on thermal perception, humidity perception and perceived air quality was closely related to standard effective temperature (SET*), humidity ratio and air enthalpy, respectively. Comfort humidity ranges were 7.9–15.1 g/kg, 3.3–18.8 g/kg and 2.9–12.8 g/kg (humidity ratio) in spring, summer and winter, respectively. Overall, our results indicate that different comfort humidity limits should be considered for different seasons in the hot summer/cold winter zones of China.

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

“…Berglund [52] experimentally demonstrated that for a sedentary person, a 30% increase in relative humidity had the same effect on the thermal balance and thermal sensation as a 1 o C increase in temperature. This is in agreement with Li et al [34], where the RH had a positive effect under cold temperatures. In his study, subjects who were on dried experimental clothes voted their thermal sensations from -2.2 to -1.3 (p < 0.05) when the RH was increased from 15% to 85% at steady state at 16 o C. Moreover, the subjects' TSV exhibited a strong linear relation with the SET.…”

“…Subjects' sensation to air humidity was referred to the evaluation of wettedness sensation [44,45], but with a slightly fine-tuned description and scale. That is, the study defined the humidity sensation and adopted the seven-point bipolar scale instead of the seven-point unipolar scale (-3: very dry, -2: dry, -1: slightly dry, 0: neutral, +1: slightly humid, +2: humid, +3: very humid), which is consistent with [34]. In addition, subjects reported their thermal/humidity acceptability on a split scale with a gap in the middle, from clearly unacceptable (-1) to slightly unacceptable (-0.1), and thereafter from slightly acceptable (+0.1) to clearly acceptable (+1).…”

“…Since the thermal conductivity of water is much greater than that of air, the effective thermal resistance of the wetted clothes would decrease [63] with an increase in moisture regain. As a result, additional sensible heat loss caused by clothes is predictable during the experiments, which results in lower MST ( Figure 4) and TSV ( Figure 10) of subjects at 85% RH, in contrast to that under dried clothing conditions [34].…”

“…With one previous study, Li et al [34] had designed a series of experiments in spring, summer and winter to examine human thermal responses under a wide range of RH levels, which based on the meteorological data in Chongqing, China. This study referred to the previous experimental design and selected the 85%RH level as a fundamental research, considering the limited exposure duration in the tests, rather than long-term exposure.…”

Effects of indoor humidity on building occupants’ thermal comfort and evidence in terms of climate adaptation

“…the relative humidity in Chongqing, which is located in a hot summer and cold winter (HSCW) climate zone, often experiences > 70% RH [4][5][6][7]. Thus, people who visit…”