Subjective Thermal Perception Research Articles

The influence of perceived control on outdoor thermal comfort: A case study in a hot summer and warm winter climate

Perceived control is a psychological state experienced by individuals in their environment and is considered a critical factor in adaptive thermal comfort models. A longitudinal study lasting two and a half years was conducted in Xiamen, China, to investigate the impact of perceived control on outdoor thermal comfort. The study, carried out in an outdoor living laboratory with 56 participants, explored conditions with and without perceived control. Subjective thermal perception and thermal environment parameters were collected. Differences in outdoor thermal comfort across summer, transition seasons, and winter between participants with and without perceived control were established, and conversion formulas for thermal sensation votes were obtained. The study results indicate that: (1) The neutral mPET of participants with perceived control were 26.4 °C, 24.9 °C, and 22.3 °C in summer, transition seasons, and winter respectively, while those without perceived control were 25.2 °C, 24.6 °C, and 22.8 °C respectively. (2) Participants without perceived control tend to prefer different thermal environment (either cooler or warmer). (3) Perceived control expanded the range of acceptable thermal environment for participants in all seasons. (4) Perceived control can reduce outdoor thermal sensitivity and make participants more likely to achieve a comfortable thermal experience, but the effect varies under different thermal conditions. (5) Regardless of perceived control, global radiation and air temperature are the most crucial environmental factors affecting thermal sensation, while the impact of clothing thermal resistance and duration of stay on thermal sensation is enhanced under conditions without perceived control.

Assessment of Outdoor Thermal Comfort in Urban Public Space, during the Hottest Period in Annaba City, Algeria

In this study; the outdoor thermal comfort of the users of two urban plazas with different morphologies in Annaba city, Algeria, have been evaluated. First, field measurements of the microclimatic parameters took place; namely the air temperature and the relative humidity in the two urban plazas, during hot days. Then, these measurements were compared with the results of the numerical simulations carried out by ENVI-met software in order to validate the model. The outdoor thermal comfort was evaluated by microclimatic measurements as well as a questionnaire survey consisting of interviews during the measurement days. The main objective was to determine the neutral Physiological Equivalent Temperature (PET) and to examine the influence of urban microclimatic conditions on the subjective thermal perception of people, as well as to compare it with different indexes of thermal comfort. Hence, the aim was to compare the microclimatic parameters of the two plazas, with and without vegetation and to see their impact on the thermal comfort indices. The results show that there is a difference between the two morphologies. Moreover, vegetation and urban morphology influence the neutral values of the thermal comfort indices.

Improving children's outdoor thermal comfort: A field study in China's severely cold regions

This study used meteorological monitoring, subjective thermal perception surveys, and activity records to explore the factors that affect children's outdoor thermal comfort in China's severely cold regions. The Universal Thermal Climate Index (UTCI) was used to determine children's thermal benchmarks and calendar, based on which a strategy to improve thermal comfort was proposed. Results showed (1) significant differences in solar radiation and wind speed, but not in air temperature and relative humidity between different areas. (2) Different Microclimate parameters affected children's thermal perception in different seasons: solar radiation (G) in winter, air temperature (Ta) in summer. (3) Children tolerate the UTCI changes in winter than in summer. (4) Children's neutral UTCI in winter and summer were 9.7 °C and 17.6 °C, respectively, and its ranges were 2.3–17.1 °C and 13.6–21.7 °C, respectively. The thermal acceptability range by 80% of the interviewed children was 2.1–16.3 °C. (5) Based on these results, a thermal comfort improvement on two dimensions—children and the environment—was implemented. This study enriches basic research on children's outdoor thermal comfort and provides a reference for the construction of urban child-friendly spaces.

The influence of virtual environment on thermal perception: physical reaction and subjective thermal perception on outdoor scenarios in virtual reality.

Positive thermal perception can affect users' climate-controlling behavior, indirectly reducing a building's operational carbon emissions. Studies show that some visual elements, such as window sizes and light colors, can influence thermal perception. However, until recently there has been little interest in the interaction of thermal perception and outdoor visual scenarios or natural elements like water or trees, and little quantitative evidence has been found associating visual natural elements and thermal comfort. This experiment explores and quantifies the extent to which visual scenarios outdoors affect thermal perception. The experiment used a double-blind clinical trial. All tests were done in a stable laboratory environment to eliminate temperature changes, and scenarios were shown through a virtual reality (VR) headset. Forty-three participants were divided into three groups randomly, separately watched VR-outdoor scenarios with natural elements, VR-indoor scenarios, and a control scenario of the real laboratory, then finished a subjective questionnaire conducted to evaluate their thermal, environmental, and overall perceptions while their physical data (heart rate, blood pressure, pulse) was real-time recorded. Results show that visual scenarios could significantly influence thermal perception (Cohen's d between groups > 0.8). Significant positive correlations were found between key thermal perception index, thermal comfort, and visual perception indexes including visual comfort, pleasantness, and relaxation (all PCCs ≤ 0.01). Outdoor scenarios, with better visual perception, rank higher average scores (M ± SD = 1.0 ± 0.7) in thermal comfort than indoor groups (average M ± SD = 0.3 ± 1.0) while the physical environment remains unchanged. This connection between thermal and environmental perception can be used in building design. By being visually exposed to pleasing outdoor environments, the positive thermal perception will increase, and thus reduce building energy consumption. Designing positive visual environments with outdoor natural elements is not only a requirement for health but also a feasible path toward a sustainable net-zero future.

Assessment of urban physical features on summer thermal perceptions using the local climate zone classification

Urbanisation has changed local meteorological conditions worldwide. The physical features of outdoor spaces are critical in determining outdoor thermal comfort through changes in meteorological parameters. Past studies comparing subjective thermal perception between local climate zones (LCZ) were mainly conducted in humid subtropical regions. This study aims to investigate this relationship using outdoor thermal comfort survey data collected in three research projects in Melbourne, Australia (temperate oceanic climate) (n = 4717). The physical features investigated included the sky view factor (SVF) and LCZ classification. During Melbourne's summer, people preferred a higher PET value than neutral PET across all LCZs. People in urban green spaces (LCZs B and C) were more likely to feel ‘neutral’ when Physiological Equivalent Temperature (PET) was 15.5 °C–24.5 °C and less likely to feel ‘slightly warm to hot’ when PET was 24.6 °C–55.6 °C. Furthermore, LCZ 6 (LCZ C) reported the highest (lowest) percentage of unacceptable votes. Cluster analysis identified two thermal comfort patterns (neutral and warm groups) representing various thermal sensations and preferences. The thermal comfort patterns proportion differed between built LCZs (5, 6) and land cover LCZs (B, C). Logistic regression revealed that PET values and urban morphology (i.e., LCZ) contributed significantly to people's thermal sensations and acceptability for neutral and warm groups. SVF significantly predicted the thermal sensation and acceptability for the warm group but not the neutral group. Our study approach informs further research to understand the implications of urban design in outdoor spaces using thermal comfort patterns as a benchmark.

Autonomic thermoregulatory responses and subjective thermal perceptions upon the initiation of thermal behavior among resting humans in hot and humid environment

BackgroundWhile thermoregulatory behavior is critical for maintaining homeostasis, our knowledge of behavioral thermoeffectors in humid heat is limited compared to the control of autonomic thermoeffectors. The predictions that the frequency and duration of intensified humid heat events are expected to increase in the coming years underline this shortcoming. Therefore, this study aims to elucidate the activation of autonomic thermoregulatory responses and subjective thermal perceptions upon deciding to initiate thermal behavior in a hot and humid environment.MethodsTen young male adults participated in an experimental trial where local cooling was permitted at any time during the behavioral assessment during passive exposure to humid heat. The air temperature and relative humidity were kept at 33^{circ }C and 80%, respectively. Skin temperatures, core body temperature (T_{text {core}}), and skin blood flow (forearm, upper arm, and upper back) were obtained 120 s preceding thermal behavior. Local sweat rate (forearm and upper arm) and subjective thermal perceptions (neck and whole-body) upon thermal behavior initiation were also recorded.ResultsMean skin temperature ({overline{mathrm {T}}}_{text {sk}}) and T_{text {core}} increased prior to thermal behavior initiation (p= 0.002; p= 0.001). An increase in mean body temperature ({overline{mathrm {T}}}_{text {body}}) was also observed (p < 0.001). However, the initiation of thermal behavior is not preceded by an increase in skin blood flow (pge 0.154) and local sweat rate (pge 0.169). An increase in thermal discomfort and skin wetness perception was observed (ple 0.048; ple 0.048), while thermal sensation did not differ from the baseline (pge 0.357).ConclusionThese findings suggest that when given the opportunity to behaviorally thermoregulate in a hot and humid environment, changes in skin blood flow and sweat rate are not required for thermal behavior to be initiated in resting humans. Moreover, an increase in {overline{mathrm {T}}}_{text {sk}} and T_{text {core}}, which appears to cause an increase in thermal discomfort, precedes thermal behavior. In addition, an increase in {overline{mathrm {T}}}_{text {body}} leading up to thermal behavior initiation was observed, suggesting that changes in {overline{mathrm {T}}}_{text {body}} rather than {overline{mathrm {T}}}_{text {sk}} and T_{text {core}} alone mediate thermal behavior in humid heat. Collectively, the results of this study appear to support the hypothesis that the temporal recruitment of autonomic thermoeffectors follows an orderly manner based on their physiological cost.

Feasibility of climate reanalysis data as a proxy for onsite weather measurements in outdoor thermal comfort surveys

Outdoor thermal comfort (OTC) surveys require synchronous monitoring of meteorological variables for direct comparisons against subjective thermal perception. The Universal Thermal Climate Index (UTCI) is a feasible index as it integrates meteorological conditions as a single value irrespective of urban morphological attributes or biological sex, age and body mass. ERA5-HEAT (Human thErmAl comforT) is a downloadable reanalysis dataset providing hourly grids of UTCI climate records at 0.25° × 0.25° spatial resolution from 1979 to present. We here evaluate for the first time whether it is possible to use ERA5-HEAT data as a proxy for the UTCI measured onsite during OTC surveys. A dataset comprising 1640 survey responses gathered over 14 OTC campaigns in Curitiba, Brazil (25°26′S, 49°16′W) was analysed. We assessed the bias obtained between the Dynamic Thermal Sensation, an index derived from the UTCI, and the thermal sensation reported by survey participants by considering locally measured meteorological variables and ERA5-HEAT reanalysis data. As ERA5-HEAT data are given on an hourly basis, prediction bias can be greatly reduced when accounting for survey responses close to the hour. In terms of seasons, the fall and winter seasons have diminished mean bias, though with larger spread than in summer. In terms of UTCI stress categories, prediction bias is lower for the thermal comfort range. When comparing reanalysis data against WMO station data as proxy candidates for survey field data, the former presented lower bias, less spread in terms of standard deviation and higher correlation to in situ data.

Using laboratory experiment to inform local adaptation policies for extreme heat events

Issuing early heat warnings and enhancing public climate change awareness and engagement are important local policy options for heat wave adaptation. Here, we used a laboratory experiment to inform major gaps in making these two policies, including setting proper thresholds for heat alerting systems and figuring out how heat experience shifts individuals’ climate change perceptions. Taking Nanjing as a case city, we simulated a heat event by increasing temperature from 25 °C to 40 °C (70% relative humidity) in a climate chamber and recruited 58 young adults as participants. Physical thermal responses, including skin temperature and heart rate variability, were recorded using portable devices. Subjective thermal perceptions, climate change belief and psychological distance were measured by self-rated scales before, during, and after the exposure. We found physiological responses were correlated with subjective thermal perceptions and showed sharp rises from 30° to 35°C, presenting aggravated thermal discomfort. Moreover, heat exposure increased climate change belief and reduced psychological distance significantly. After the experiment, follow-up surveys showed participants had a short memory of the heat exposure, but daily temperature variations still predicted climate change belief. The findings suggest in our case city, the current threshold (35 °C) for heat warnings may not be safe enough. Local authorities should consider prolonged periods of hot weather with temperature between 30 and 35 °C. Due to strong links between heat experience and climate change perceptions, we encourage to take this “window of opportunity” when heat events occur to communicate climate risks and enact post-event policy changes.

Urban climate walk: A stop-and-go assessment of the dynamic thermal sensation and perception in two waterfront districts in Rome, Italy

This study set out to understand the dynamics of human thermal sensation and perception associated with outdoor thermal variability in urban contexts. Previous studies found that compact urban forms and green features can contribute to urban climate diversity, and conjectured whether the wax and wane of thermal stress can promote thermal satisfaction in outdoor public spaces. Hence, a stop-and-go method has been developed to accurately capture thermal transitions along urban walks and to provide snapshots of the momentary body thermal sensation and subjective thermal perception. The measurement campaigns carried in late summer involved a total of 40 participants walking for 70 min through two waterfront districts in Rome, Italy. Our findings indicate that: (1) the oscillation of air temperature along the dense urban walk (R2=0.74) is nearly twice as frequent as that along the sparse suburban walk (R2=0.23), due to the microclimatic diversity shaped by the compact urban fabrics, pocket parks and tree-lined river banks; (2) the Universal Thermal Climate Index (UTCI) contrast can effectively predict thermal alliesthesia (R2=0.34) measured by the rate of change of mean skin temperature (d(Tmskin)/dt < 0.012°C∙min−1); (3) subjective perception shows a significant trend but a poorer model fit (R2<0.25) predicted by UTCI and Tmskin; (4) two confounders, view and social backgrounds, are proved to affect the regression model between the objective and subjective data. The conclusions emphasise the importance of incorporating spatial and social contexts into the investigation of outdoor thermal comfort via physiological and psychological approaches.

Physiological Indices and Subjective Thermal Perception of Heat Stress-Exposed Workers in an Industrial Plant

This study aimed to investigate the thermal responses of acclimated workers exposed to heat stress in a real work environment. The physiological indices and subjective thermal perception of the 14 acclimated workers were measured in an industrial plant. The effects of wet bulb globe temperature (WBGT) on physiological indices and subjective thermal perception were studied. The differences in thermal responses between the acclimated workers and unacclimated college students exposed to heat stress were compared and analyzed. The relationship between the mean skin temperature and the thermal sensation was revealed. The results show that the mean skin temperature, oral temperature, and heart rate of the acclimated workers increase with WBGT, while the blood pressure decreases with WBGT. Compared with the unacclimated college students, the acclimated workers felt more comfortable and tolerant under the same heat stress. The thermal neutral mean skin temperature of the acclimated workers is 32.3 °C, which is approximately 1.0 °C lower than that of the unacclimated college students. The results of this study can help ensure the occupational safety and health of heat stress-exposed workers.

Effects of local heating of body on human thermal sensation and thermal comfort

Cold climates are conductive to heavy reliance on mechanical heating, increasing energy consumption. The use of personalized local heating can save energy, but the thermal perception capabilities of different body parts to local heating remain unclear. In this study, 32 participants wore clothing with an insulation rating of 0.9 Clo in a cool environment maintained at 19 °C. Each of seven body parts (back, chest, belly, waist, buttock, knee, and foot) was locally heated for 15 min using a heating pad taped to the outside of the undergarment at a temperature of 32±1 °C. The overall and local subjective thermal perceptions were captured using a questionnaire. Local heating devices with fixed surface temperatures significantly improved thermal sensation and comfort in cool environments. Heating the waist was associated with a significant improvement in overall thermal perception (p < 0.05), while heating the knee and chest showed the least improvement. Heating the waist increased the overall thermal sensation from slightly cool (−0.78) to neutral (0.26) and the overall thermal comfort from slightly uncomfortable (−0.50) to slightly comfortable (0.47), which was better than heating the foot. The effect of local heating was different between genders, with improvements being characterized as increased thermal sensation for men and increased thermal comfort for women. Local heating also reduced the heart rate, again with this reduction varying with the body part being heated. The acceptability of local heating was 81%, showing that it can be widely used in practice.

Dynamic effects of frequent step changes in outdoor microclimate environments on thermal sensation and dissatisfaction of pedestrian during summer

• Subjects’ dynamic thermal responses to frequent microclimatic step changes are investigated. • Comparison between surveyed dynamic thermal sensation and predicted sensation is made. • Equivalent UTCI* based on SWI and frequent step change effectiveness is proposed. • Applicability of UTCI* in evaluating thermal sensations under frequent step changes is evaluated. • Impacts of frequent microclimatic step changes on thermal dissatisfaction in summer are revealed. Humans engaging in outside activities are more likely to be exposed to frequent spatiotemporal step changes in outdoor thermal conditions, as opposed to constant thermal conditions staying indoors. Understanding pedestrians’ thermal reactions to such dynamic thermal settings is helpful for enhancing outdoor thermal comfort by providing spatiotemporal variations in thermal conditions. In this study, 48 subjects were tested about their thermal perceptions while being exposed alternately to direct sunlight and shade at different defined frequencies, in a series of 45 min experiment period. The experiments were designed to create step changes in microclimate environments. The study was carried out from May to July in a university campus in Hong Kong with subtropical weather conditions. Results show that subjective thermal perceptions varied with alternating exposure to sunlight and shade at different frequencies. UTCI was modified to an equivalent UTCI* for evaluating thermal environments with frequent step changes by taking into account impacts of mixed changes in sun and wind conditions, alternating frequency and expectation on thermal perceptions. With a higher alternating frequency, there was reduced thermal dissatisfaction with hot summer days and a lower comfort requirement for shade, as well as the upper limit of acceptable UTCI* approaching 43.7 °C.

Outdoor thermal comfort improvement with advanced solar awnings: Subjective and objective survey

The aim of this work is to enhance microclimate and pedestrians’ thermal comfort under solar awnings. For this purpose, an optimized awning with aluminized polyester film, characterized by low thermal emissivity properties downward and high thermal emissivity upward, was tested and compared with a high thermal emissivity white textile awning, usually used for outdoor solar shadings. The two awning configurations were tested in summer 2021 through a combination of micrometeorological monitoring and an outdoor thermal comfort survey. An objective thermal comfort evaluation was carried out through micrometeorological data monitoring under both awnings, used to determine the modified Physiological Equivalent Temperature (mPET), through the application of the RayMan model. A subjective thermal perception, preference and thermal comfort evaluation under the two configurations were collected by the outdoor thermal comfort survey. The comparison between the subjective thermal comfort sensation and the objective thermal comfort index evaluation allowed to determine the effectiveness of the proposed awning solution for the enhancement of outdoor thermal comfort. The optimized awning allows to reduce the mPET values on an average of 1.6 °C and a maximum of 5.1 °C.

Study on the outdoor thermal comfort evaluation of the elderly in the Tibetan plateau

China's aging population is an increasingly serious concern. Adding outdoor space can increase the frequency of outdoor activities of the elderly and effectively improve their quality of life. In this study, Lhasa was used as an example. We examined the thermal comfort of a typical outdoor activity space for the elderly during winter and summer. Microclimate measurements and a questionnaire survey were administered to the participants on typical days during winter and summer, and the outdoor thermal environment sensitivity, sex differences in thermal sensation, thermal neutral physiological equivalent temperature (PET), and comfort range of the elderly in the Tibetan Plateau were calculated and analyzed. A regression model was established between the sensitive thermal environmental indicators and the subjective thermal perception to explore the influence of thermal environmental indicators on the expectations of the elderly. The following results were obtained. 1. The elderly in Lhasa were more sensitive to changes in the thermal environment during winter than during summer. During winter, the wind was the most sensitive factor, while sunshine was the most sensitive factor during summer, and the sensitivity of women was higher than that of men. The mean radiation temperature (Tmrt) and wind speed (Va) were the climate parameters most sensitive to changes in the thermal environment. 2. The annual outdoor neutral PET of the elderly in Lhasa was 20.6 °C. The outdoor neutral PET in winter was 12.76 °C/11.08 °C, and the outdoor neutral PET in summer was 25 °C/22.14 °C. Moreover, there were differences between the thermal comfort of neutral PET of the elderly in other climatic regions and those in Lhasa, especially between the lower limits. 3. During winter, the elderly preferred a higher average radiation temperature to meet the needs of thermal comfort, while during winter and summer, the elderly preferred a lower wind speed.

Meta-analysis of outdoor thermal comfort surveys in different European cities using the RUROS database: The role of background climate and gender

Systematic comparisons of subjective thermal assessments among different geographical locations and between different genders are quite limited. This paper presents a meta-analysis using the data of comprehensive European outdoor thermal comfort (OTC) surveys. The aim is to reveal the common traits and the major differences regarding the subjective thermal perception and sun preference of residents in different European cities while taking great emphasis on the role of genders. The analysis relies on the RUROS (Rediscovering the Urban Realm and Open Spaces) project which was conducted in seven European cities, and the Hungarian OTC project. Only acclimatized local residents were considered to reflect the geographical and possibly cultural differences among the population of the investigated cities. The resulted neutral temperature values – expressed in terms of Physiologically Equivalent Temperature (PET) and determined by means of regression analysis – showed strong correlation with the long-term climatic characteristics, and narrower neutral zone was found at those locations where the annual temperature amplitude was small. Inhabitants of sunny and warm cities did not prefer more sunshine even when the actual sunshine value was low, while where the annual amount of sunshine was low the people showed greater sun preference. European women were found to perceive the thermal conditions as neutral under slightly warmer conditions than men and showed greater sensitivity to the changes of the environmental conditions. This was evidenced by narrower neutral PET zone of females and stronger correlation between their sun preference and the actual value of solar radiation.

How correlated color temperature (CCT) affects undergraduates: A psychological and physiological evaluation

The luminous environment had a significant influence on the working efficiency, especially for the learning efficiency of undergraduates. Correlated color temperature (CCT), as an important evaluation parameter of luminous environment, affects the learning efficiency and fatigue obviously, so it is important to select the suitable CCT for classrooms. To explore the comprehensive influence of CCT on undergraduates and thereby, find the suitable CCT in different environments for classrooms, a classroom model was built with 6 CCTs (3000K, 3700K, 4400K, 5100K, 5800K, and 6500K) under three air temperatures of 23 °C, 26 °C and 29 °C. The questionnaire survey was conducted to analyze the subjective feeling including thermal sensation, thermal comfort and CCT satisfaction for 32 undergraduates, while the experiment was done to measure the attention and relaxation of undergraduates under the different luminous environment. The questionnaire results showed that the thermal sensation vote reduced by 1.65–2.75 when CCT increased from 3000K to 6500K, and the same thermal sensation of slightly warm (TSV = 1) was achieved when CCTs were 3000K, 4400K and 5800K at 23 °C, 26 °C and 29 °C, respectively. These indicated that CCT could obviously regulate the subjective thermal perception at different air temperatures. The fitting analysis of subjective perception and physiological parameters showed that the average attention and relaxation were the highest when the thermal sensation was slightly cool (TSV = −0.40) and slightly warm (TSV = 0.59), respectively. And moderate thermal comfort (TCV = 0.03) maximized the average attention, and increased thermal comfort increased the relaxation. The suggested CCTs for learning were 4400K–5100K, 5100K–5800K, and 5800K–6500K of 23 °C, 26 °C and 29 °C, respectively. And the suggested CCTs for rest were 3700K–4400K, 4400K–5100K, and 5800K–6500K of 23 °C, 26 °C and 29 °C, respectively. This provides a comfortable and efficient lighting environment for undergraduates.

A comparative study of gender differences in thermal comfort and environmental satisfaction in air-conditioned offices in Qatar, India, and Japan

Gender differences in the assessment of thermal comfort and indoor environmental quality (IEQ) in the Gulf Cooperation Countries (GCC) have not previously been investigated, despite the prevalence of the overcooling of indoor spaces. This study investigated the effect of sex, age and body mass index on subjective thermal comfort perceptions, comfort temperature and IEQ satisfaction in offices using our thermal comfort surveys in Qatar, India, and Japan. Data from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) databases were used for comparison. We found that females were twice as likely to feel dissatisfied with thermal sensation than males in Doha. Overall, females felt colder than men, and were less satisfied with all IEQ parameters. In Doha, females, younger subjects, and high-BMI subjects had lower comfort temperatures than their counterparts.Increased indoor air speeds and the provision of personal environmental controls could effectively reduce female dissatisfaction and save energy in Qatar. Women's more stringent thermal comfort preferences could be used to evaluate occupant control provisions and IEQ standards. A robust IEQ complaint redressal system may also be required in offices. This study highlights the need to consider female perspectives and thermal expectations in the environmental design of workplaces as well, not merely privacy concerns.

The influence of a moderate temperature drift on thermal physiology and perception

Humans spend approximately 80–90% of their time indoors. In current practice, indoor temperatures in many buildings are controlled very tightly. However, allowing more variation in indoor temperature results in more energy-efficient buildings and could potentially improve human metabolic and cardiovascular health. Therefore, this study aimed to evaluate the effect of a drifting ambient temperature versus a fixed ambient temperature on thermal physiological parameters and subjective perception. A cross-over intervention design was conducted in 16 healthy men (age 26 ± 4 y; BMI 23.0 ± 1.7 kg/m2) between July 2018 and May 2019. All participants underwent two whole-day (8:30–17:00) experimental sessions, during which they were exposed to a drifting (17–25°C with a morning ramp of 2.58°C/h and afternoon ramp of -2.58°C/h) or constant ambient temperature (21°C) in randomized order. The experiments took place in respiratory chambers, which simulated a typical office environment and in which temperature conditions can be controlled accurately. Throughout the experimental sessions core and skin temperature, heart rate, blood pressure, energy expenditure as well as activity levels were measured. Subjective thermal perception, such as thermal comfort and sensation, was assessed by questionnaires every 30 min. Results reveal that energy expenditure was higher in the morning during the drifting session, which was accompanied by an increase in activity levels. Both drifting and fixed sessions were judged as comfortable although during the drift thermal comfort was lower in the morning and afternoon and higher during midday. The results indicate that a drifting ambient temperature can be applied in practice, and as such, can contribute to a healthier and more sustainable built environment. More research is needed to understand the role of a drifting temperature on the long term.

Differences in environmental perception of gender and sleep quality in self-regulating sleep thermal environment

This study was to explore gender differences in response to subjective comfortable thermal environment by performing human experiments in summer. A total of six discontinuous conditions for self-regulating ambient temperature were designed with five males and five females. Sleep onset latency and slow wave sleep, from the physiological indices of electroencephalograph, electromyography and electrooculography, measure sleep quality objectively. Results indicate that gender differences in subjective temperature preferences, thermal sensation and sleep quality are reflected by temperature or temperature intervals. In particular, women have a significantly higher temperature range than men. Meanwhile, the temperature sections of males and females corresponding to thermal sensation and sleep quality are summarized under the same thermal resistance. Moreover, the results of temperature difference between men and women on thermal perception and sleep quality showed that the temperature difference of subjective sleep quality coincides with the objective one, but greater than the subjective thermal perception results implying that a greater discrepancy between males and females in sleep thermal physiological needs than during their awake.

Passive space design, building environment and thermal comfort: A university building under severe cold climate, China

In this paper, the building environment and the thermal comfort of occupants were investigated at a university building located in severe cold climate zone in the northwest of China during winter, transition and summer. First, in the two typical weather days of the year, the thermal environment of the Shihezi University building with atrium and courtyard was measured on the spot to investigate the impact of passive space design on the thermal environment of the building. Second, a questionnaire survey was used to report occupants’ subjective thermal perception and environmental variables were measured simultaneously. A total of 1346 valid subjective questionnaires and measurement data were obtained. The results showed that the thermal neutral temperature analysed by linear regression in winter, transition and summer were 24.42°C, 24.64°C and 28.10°C, respectively. The thermal comfort temperature range was from 19.59 to 29.44°C (winter) and 23.32 to 28.52°C (transition and summer). The occupants’ preference temperature was 25.14°C and 24.35°C in winter and transition. The adaptive behaviours of clothing adjustment and opening windows were closely correlated to the indoor operative temperature. Third, the correlation between indicators of thermal comfort, including subjective feelings and objective factors was also analysed.