Effects of body geometry, body composition, cardio-pulmonary capacity, and fitness on young men's thermal preference.

This paper investigated principal parameters affecting individual differences of thermal preference. 36 male college students were selected from three thermal preference groups by a questionnaire, including 10 of cool preference (Gcp), 17 of neutral preference (Gnp), and 9 of warm preference (Gwp). Subsequently, their thermal preferences were further examined by a human trial in a climate chamber. Once significant differences were found between groups, subjects' 57 parameters, including body geometry, body composition, cardio-pulmonary capacity, and physical fitness, were measured. Compared to Gwp, Gcp had higher weight (80.0 vs. 64.2 kg), body mass index (BMI) (26 vs. 20.8 kg·m-2 ), body surface area (BSA) (1.94 vs. 1.78 m2 ), waist-to-hip ratio (WHR) (87.29% vs. 80.23%), body circumferences (except for forearm circumference), skinfold thickness of all the local parts, volume of expired air (VE) (50.97 vs. 40.81 L/min), and body fat rate (BFR) (24.44% vs. 14.07%), but had a lower specific surface area (SSA) (0.02477 vs. 0.02791 m2 /kg), resting metabolic rate (RMR) per kilogram (1.21 vs. 1.47 W/kg), diastolic blood pressure (DBP) (65.30 vs. 74.69 mmHg), and percentages of muscle (71.17% vs. 80.95%), total water (55.35% vs. 63.14%), skeletal muscle (42.47% vs. 47.94%), protein (14.90% vs. 16.94%), inorganic salt (5.29% vs. 5.86%), and bone mineral (0.044% vs. 0.048%). Among these parameters, body fat and SSA played a dominant role (accounting for 85.76%) in explaining individual differences in thermal preference.

Associations of indoor carbon dioxide concentrations, air temperature, and humidity with perceived air quality and sick building syndrome symptoms in Chinese homes.

The indoor environment influences occupants' health. From March 1, 2018, to February 28, 2019, we continuously monitored indoor temperature (T), relative humidity (RH), and CO2 concentration in bedrooms via an online system in 165 residences that covered all five climate zones of China. Meanwhile, we asked one specific occupant in each home to complete questionnaires about perceived air quality and sick building syndrome (SBS) symptoms at the end of each month. Higher CO2 concentration was significantly associated with a higher percentage of perceived stuffy odor and skin SBS symptoms. Higher relative humidity was associated with higher percentage of perceived moldy odor and humid air, while lower RH was associated with a higher percentage of perceived dry air. Occupants who lived in residences with high RH were less likely to have mucosal and skin SBS symptoms (adjusted odds ratio (AOR): 0.73-0.78). However, the benefit of high humidity for perceived dry air and skin dryness symptoms is weaker if there is a high CO2 concentration level.

Air change rates in urban Chinese bedrooms.

The ventilation modalities in most Chinese residences are infiltration and opening windows. We measured infiltration rates and air change rates at night, with no attempt to change occupants' behaviors, of urban residences in five climate zones of China during four seasons. Using the CO2 decay method, we found the median infiltration rate for 294 residences to be 0.34 h-1 . Using occupant-generated CO2 as tracer gas, we determined air change rates over the course of 1 year in 46 bedrooms at night from mass balance considerations. In 54% of the measurements, windows were closed, so ventilation was only by infiltration. Windows were mainly closed when the outdoor temperature was below 15°C and above 26°C. The median infiltration rates did not differ appreciably among seasons and climate zones and were always less than 0.45 h-1 .

The key local segments of human body for personalized heating and cooling.

Thermal characteristics of local body parts of a human subject are markedly different in cold or hot environments. Some body segments are known to be much more susceptible to heat loss than the others, thus strongly influencing the overall thermal sensation of a subject. If these body parts can be effectively cooled in a hot environment or warmed in a cold environment using personal environmental control systems, thermal comfort of human occupants can be achieved at the minimum cost of energy without heavily relying on centralized heating, ventilation, and air conditioning systems. With an objective to understand the influence of local thermal sensation on the subjects' overall thermal comfort perception, experiments in the two sets of climate chambers were carried out simulating summer and winter conditions, respectively. A total of 24 subjects (12 females and 12 males) were recruited for this study, and their local skin temperature, conductive heat flux, and thermal sensations were recorded during the experiments. The local thermal characteristics of the subjects were compared between the 'neutral' and 'hot' conditions to identify predominant body segments in the summer scenario. Moreover, the comparison was also made between the 'neutral' and 'cold' conditions to derive predominant body segments in the winter scenario. The analysis of the results indicated that leg, thigh, and back are the key segments desirable for local cooling; whilst leg, thigh, back, and upper arm are the crucial segments for local heating. The findings can have important implications for the design of low-energy cost-effective personal heating/cooling devices. Finally, the results identified the conductive heat flux of skin as a useful physiological parameter in examining human thermal sensation.