Subjective Thermal Sensation Research Articles

Assessing Thermal Comfort in Hot and Humid (Tropical) Climates: Urban Outdoor and Semi-outdoor Conditions in Waiting Areas of Railway Stations

The global phenomenon of global warming has intensified thermal discomfort in tropical metropolitan areas, where rising temperatures and the urban heat island significantly impact outdoor and semi-outdoor environments. These effects are particularly pronounced in tropical metropolitan areas, where the hot and humid climate exacerbates thermal stress. Despite the critical need to understand thermal comfort in such settings, existing research remains limited. This study addresses the research gap by examining how global warming affects thermal comfort in outdoor and semi-outdoor urban spaces, providing insights into the unique challenges these environments present. The study sought to assess both objective physical data and subjective Thermal Sensation Votes (TSV) and preferences. The results suggest that the temperature neutrality needed for thermal comfort is 29.02°C (R2 = 0.95), and a temperature comfortable range of 23.84–30.79°C (R2 = 0.84) is within the acceptable comfort level. This range surpasses the current averages, emphasizing the importance of environmental enhancements for better thermal comfort. The regression analysis indicates that operational temperature (To), mean radiant temperature (Tmrt), and body mass index (BMI) are significant variables that may accurately predict thermal sensation. Furthermore, results indicate that individuals with a higher BMI often have a reduced ability to withstand elevated temperatures. This study emphasizes the need of considering both environmental and human factors in order to improve the human comfort level and quality of life.

Assessing thermal comfort in wooden buildings: A visual perceptual analysis through physiological characterization

As the use of wood, a representative low-carbon building material, increases to reduce greenhouse gases, analysis of the impact of wood spaces on occupants is important for effective environmental planning. Therefore the study delved into the visual and perceptual warmth effects of wood through a comparative of thermal sensations in spaces featuring various finishing materials. A living space was created using concrete, wallpaper, brick, and wood, respectively, through virtual reality. A total of 30 subjects experienced the four living spaces through virtual reality, while subjective thermal sensation questionnaires and four physiological responses were measured. In a slightly cool environment based on predicted mean vote, subjects ranked the perceived warmth in the following order: wood > brick > wallpaper > concrete, with wood surpassing concrete by 3.30, in terms of visual warmth. These results support the hue-heat hypothesis that materials in the yellow–red spectrum are commonly perceived as warm. Moreover, the representative psychological impression associated with wood, such as warmth and coziness, considerably influences these perceptions. Importantly, the positive impact of the visual and perceptual thermal effects of wood, alongside the impression of space (as being comfortable, positive, and relaxed), notably enhanced thermal comfort, especially in cooler conditions. Furthermore, the subjective evaluation of the thermal environment was validated through correlation analysis involving thermal perception biomarkers and thermal comfort model. Indoor spaces with wood finishing materials were perceived as warm, and the possibility of reducing heating load and greenhouse gas emissions was suggested by improving thermal comfort during the heating season

Mechanism underlying the influence of humidity on thermal comfort and stress under mimicked working conditions

Thermal comfort in an office impacts physical health, stress, and productivity. Humidity affects thermal comfort; however, the underlying mechanism remains unclear. This study assessed the influence of humidity on body temperature, thermal comfort, stress, and their relationship in working individuals. Thirteen participants performed three sets of 20-min calculation tasks followed by a 10-min rest in 26 °C or 33 °C with relative humidity (RH) of 30 % or 60 %. Core body temperature (Tcore), mean skin surface temperature (Tskin), and electrocardiogram were continuously recorded. Subjective thermal sensations and comfort were assessed with visual analog scales. Stress level was estimated based on α-amylase activity and immunoglobulin A level in saliva and heart rate variability. Mean Tskin and Tcore elevated at 33 °C with 60 % RH, where warm sensation and thermal discomfort also increased. Heart rate variability reflecting parasympathetic nerve activity decreased. There was a negative linear relationship between weighted body temperature and thermal comfort. However, thermal discomfort was augmented at a given weighted body temperature at 60 % RH. Thus, under indoor working conditions, high humidity may augment thermal discomfort and become a stress factor. Increases in Tskin and Tcore are involved in the mechanism, alongside other factors.

Research on the evaluation of occupants' work efficiency in summer thermal environment of special vehicles based on subjective thermal sensation

High summer temperatures in special vehicle cabins affect drivers and occupants, reducing efficiency and combat potential. Improving occupant work efficiency is key to enhancing overall combat effectiveness. There's a lack of research on the work efficiency of special vehicle occupants engaged in complex, specialized tasks within cabin thermal environments. This study focused on a special vehicle, discussing the effects of the summer thermal environment in the cabin on personnel efficiency. It linked subjective thermal sensations to work efficiency through questionnaires and task performance evaluations. The best work efficiency environment may not be the environment with the highest thermal comfort. This paper presented a subjective thermal sensation range criterion for maintaining the work efficiency of the occupants in the cabin during the summer. This serves as a basis for optimizing the summer thermal environment and improving the reliability of human-vehicle systems in special vehicle cabins.

Thermal perception of infrared radiation applied at different wavelengths to distal body segments in neutral and cool ambient environments

Personal Comfort Systems (PCS) hold the promise of simultaneously improving energy conservation and occupants’ thermal comfort. Locally applied thermal radiation is one of the most common PCS strategies for cool ambient environments. This study examines the subjective impacts of different infrared wavelengths applied to distal body segments of human subjects sitting quietly in cool and neutral environments. Experiment participants were exposed to three different wavelengths (near-infrared, mid-to far-infrared, and far-infrared), each of approximately equal flux density, on the backs of hands, lower arms, and lower legs, in both neutral (26.0 °C operative temperature) and cool (21.5 °C operative temperature) ambient environments within the chamber. Skin temperature, along with subjective thermal sensation and thermal pleasure votes were recorded throughout each exposure experiment. In the cool environment, similar to the neutral environment, far-infrared radiation increased skin temperature more than near-infrared and elicited warmer subjective thermal sensations and thermal pleasure responses. Of the three distal body segments examined, the back of the hands was most sensitive to the different wavelengths and was associated with the strongest and fastest pleasure response at the onset of radiant heating during the cool ambient environmental exposures. These findings have implications for PCS design, suggesting that irradiating the back of the hand with far-infrared wavelengths at the onset of PCS use may maximize thermal comfort of sedentary occupants in cool ambient conditions for a given power input.

Evaluating and comparing objective and subjective thermal comfort in a malaysian green office building: A case study

This study examined thermal comfort in a sustainable office building in Malaysia, with the goal of understanding how objective environmental data relates to occupants' subjective experiences. The study utilized established thermal comfort models, such as the predicted mean vote (PMV), in conjunction with occupant surveys to evaluate the indoor environment. Objective data aligned with thermal comfort criteria, but subjective thermal sensation vote (TSV) showed a notable difference. The environment felt colder than anticipated by the occupants. This study emphasises the drawbacks of depending exclusively on conventional thermal comfort models, especially in tropical settings. The research emphasises the importance of considering individual variability (physiological and psychological), localised environmental variables, and potential adaptive comfort mechanisms impacted by regional climate. This research aims to develop a thorough understanding of green buildings' inside climates to inform design methods for achieving optimal thermal comfort, energy efficiency, and reduced carbon emissions. The results provide guidance on methods for emphasising occupant-centered design in sustainable buildings located in tropical areas. This study focuses on filling the knowledge gaps regarding the dynamics of thermal comfort in green buildings located in tropical regions. Combining empirical data with subjective feedback emphasises the need for design strategies that focus on occupant well-being in addition to energy efficiency goals.

Cold hypersensitivity in the hands and feet is associated with erectile dysfunction in young Taiwanese men

Cold hypersensitivity in the hands and feet (CHHF) is a protective or predisposing factor for many diseases; however, the relationship between CHHF and erectile dysfunction (ED) remains unclear. We aimed to investigate associations between CHHF and ED among young men of Southeast Asian origin. In this cross-sectional study, sexually active Taiwanese men aged 20–40 years were enrolled via an online questionnaire comprising general demographic information, comorbidities, subjective thermal sensations of their hands and feet in the past 6 months, and their erectile function using the International Index of Erectile Function-5 (IIEF-5). Participants who reported cold sensation of hands and feet were classified to have CHHF; those with IIEF-5 score ≤ 21 were considered to have ED. Total 54.2% and 27.9% of participants had ED and CHHF, respectively. Men with CHHF were significantly younger, had lower body mass index and IIEF-5 scores (p < 0.001), and a lower prevalence of diabetes mellitus (p = 0.033) along with higher prevalence of ED, psychiatric disorders, and insomnia (p < 0.001). After adjusting for predisposing factors of ED, CHHF (odds ratio 1.410, 95% confidence interval 1.159–1.714; p = 0.001) remained an independent predictor of ED. Thus, CHHF is independently associated with ED, affecting more than a quarter of young Taiwanese men. Autonomic dysregulation and subclinical endothelial dysfunction may be common pathophysiologies of CHHF and ED.

An integrated thermal sensation scale for estimating thermal strain in water

Acceptable definitions of thermal sensation for cold and hot water immersion do not exist. The use of subjective thermal sensation scales remains unsolved with broad psycho-physiological, and semantic implications. We hypothesize that perception of thermal sensation could be a valid and reliable indicator for thermal strain during exposure in water. We aimed to provide a theoretical background for behavioral thermoregulation and neurocognition to support an integrated thermal sensation scale for estimation of thermal load during head-out water immersion. This research used a mixed methods approach. Domains were identified and items were measured for thermal load to examine the content validity. Thereafter, we formed an integrated scale based on standard 10,551 of International Organization for Standardization (ISO). Finally, we conducted a pilot study for the face validation of the scale based on a 30 min head-out water immersion at 26 °C in healthy adults (females, n = 4; males, n = 4; age: 22.6 ± 8.0 years; body mass, 67.7 ± 9.5 kg; height, 169.0 ± 5.6 cm). We identified three aspects (environment, physiological and behavioral thermoregulation) and a total of 18 items, of whom eight items (water temperature, immersion duration, core temperature, skin temperature, body heat storage, shivering, thermal sensation, and thermal comfort) were acceptable based on terms of scale-level content validity index (S-CVI = 92 %). Conditions incorporated into our scale included: icy < 12 °C, cold 12–24 °C, cool 24–29 °C, neutral 29–38 °C, warm 38–43 °C, and hot > 43 °C. We found excellent face validity based on a reported homogenous cool feeling and physiological thermoregulatory responses. Our study revealed our model could reasonably characterize body thermal load though whole-body thermal sensation based on well-established thermoregulatory mechanisms during water immersion. Further research is needed to validate the accuracy of our behavioral model in a variety of water temperatures and in a larger sample size.

Influences of Indoor Air Temperatures on Empathy and Positive Affect.

The consequences of climate change are already visible, and yet, its effect on psychosocial factors, including the expression of empathy, affect, and social disconnection, is widely unknown. Outdoor conditions are expected to influence indoor conditions. Therefore, the aim of this study was to investigate the effect of indoor air temperature during work hours on empathy, positive and negative affect, and social disconnection. Participants (N = 31) were exposed, in a cross-over design, to two thermal conditions in a simulated office environment. Questions on empathy and social disconnection were administered before and after the exposure to each condition, while affect was measured throughout the day. Subjective thermal sensation and objective measures of mean skin temperature were considered. The results indicated a significant difference in empathy (F(1, 24) = 5.37, p = 0.03, with an η2 = 0.126) between conditions. Participants reported increases in empathy after exposure to the warm condition compared to the cool condition, in which reductions in empathy were reported. Although the same pattern was observed for positive affect, the difference was smaller and the results were not significant. Thermal sensation had a significant effect on changes in empathy too (F(1, 54) = 7.015, p = 0.01, with an R2 = 0.115), while mean skin temperature had no effect on empathy (F(1, 6) = 0.53, p = 0.89, with an R2 = 0.81). No effects were observed for positive and negative affect and social disconnection. Longitudinal studies are needed to support these findings.

Human thermoregulatory model for simulating thermal response in high-temperature and hypobaric environments

The main function of the human thermoregulation system is to maintain the stability of body temperature. When fighters and helicopters are performing high-altitude combat tasks, pilots are often exposed to hypobaric conditions and high-temperature environments, causing thermal discomfort and a reduction of physical and mental abilities. This research starts with the improvement of the previous thermoregulatory model for the human body by revising the convective and evaporative parameters of the environment, and the metabolic parameters of thermoregulation in hypobaric conditions. Then thermal physiology experiments were carried out on the ground and at 4000 m altitude. The sweating volume, local skin temperature, and subjective thermal sensation scales were measured to explore the human thermal regulation mechanism and validate the accuracy of simulation results. For comparison of simulation and experiments, the average skin temperature errors are 0.37 °C and 0.24 °C, and the relative errors of the sweating volume are 9 % and 8 % in the atmospheric and hypobaric environments, respectively. The results indicate that the improved thermoregulatory model for simulating thermal response could realize accurate predictions in high-temperature atmospheric and hypobaric environments.

Outdoor thermal perception in the semi-arid climate of Constantine, Algeria: A field survey during the post-COVID-19

The purpose of the paper was to assess pedestrians' thermal perception, in the semi-arid climate of Constantine, Algeria, with particular emphasis on the protocols implemented in public spaces during the post-COVID-19. Three outdoor public spaces were selected in August 2021 to conduct a field study involving 254 respondents, randomly assigned. The adopted approach combined objective and subjective assessment, as well as numerical simulations using ENVI-met. Accordingly, microclimate monitoring and a questionnaire survey were carried out simultaneously from 7 a.m. to 7 p.m. in each study site. A strong association was found between the combined microclimate parameters (objective variables) and thermal sensation of the surveyors with (R2 = 0.74). Besides, Kruskal-Wallis H test revealed that the subjective thermal sensation was significantly influenced (p-value <0.05) by thermal history and purpose of visit (subjective variables). Most interviewees preferred ‘move to shade’ measure as a remedial behavior to reduce their thermal discomfort. Further, a neutral temperature of 22.7 °C PET was obtained by a linear regression between the Mean Thermal Sensation Votes (MTSV) and Physiological Equivalent Temperature (PET), the comfort range was estimated between 18.6 °C ≤ PET≤ 26.8 °C during summer. Regarding the COVID-19 pandemic effects, the Chi-square test suggests that the frequency of pedestrian visits was statistically independent of the imposed pandemic measures. However, the planned activities were affected by social distancing and the use of face masks increases pedestrians' thermal discomfort. Overall, the study highlights the significance of environmental and non-environmental factors to improve outdoor thermal comfort, and ensure human well-being.

Quantification of visual thermal perception changes in a wooden interior environment using physiological responses and immersive virtual environment

Wood can be used for various applications, such as for carbon storage, to enhance structural strength, and to promote biophilia; additionally, wooden building can positively affect the carbon footprint and well-being of occupants through changes in the thermal sensation by hue-heat hypothesis-based visual effects. However, previous studies focusing on the visual effect of indoor wood have limitations in terms of physical model implementation and subjective evaluation. In this study, an indoor wood application model is implemented using Virtual reality, and the subjective thermal sensation is quantitatively measured through physiological response measurement. The occupant's subjective thermal sensation is higher in the wood condition than in the nonwood condition and the occupant feels warmer as the level of wood application is increased. Physiological response, skin temperature, electrodermal activity, and electroencephalogram exhibit significant differences according to the level of wood application and similar tendencies to the data measured for the prediction of thermal sensation in previous studies. Using VR, the increase in the thermal sensation of occupants through the visual effect of wood without temperature control is confirmed through objective physiological parameters.

Adaptive thermal comfort of residential buildings in the composite climatic region of India: a field study

ABSTRACT This paper presents the results of an adaptive thermal comfort field study conducted in the naturally ventilated residential buildings in the composite climate type of India over three main seasons i.e. monsoon, winter, and summer using ASHRAE’s class II field measurements protocols. 768 measurements were collated wherein subjective thermal comfort sensation, preference, and acceptance for indoor environment variables were thoroughly explored along with the adaptive actions of the users for four different times during a day. Correlation analysis helped decipher the relationship between subjective votes and thermal comfort evaluation parameters. Thermal environment acceptance during monsoon season and morning time was highest however the same was found lower during summers and afternoons. The middle age group had the lowest acceptance and well-acclimatized non-native participants had a good thermal acceptance. Education also affects thermal acceptance and it decreases with increasing education level. The comfort temperature and adaptive comfort equation were also studied and results were compared with national and international thermal comfort standards. This study predicted a wider thermal comfort range of 12.23–34.45°C and indicated revising TSI, the first thermal comfort index for Indian Subjects.

Emergency heater based on gas-fired catalytic combustion infrared technology: Structure, evaluation and thermal response

Deaths caused by extreme cold occur frequently, emergency heating needs to be greatly enhanced. In present work, a porous media catalytic combustion emergency heater was designed with a self-developed 1% Pt/Al2O3·SiO2 catalyst. Some evaluation indicators of the natural diffusion heater (including thermal efficiency, combustion efficiency, ignition temperature, cold start performance, combustion plate temperature uniformity, and infrared wavelength distribution) were established experimentally. According to the results, the catalyst possesses high activity (T50 = 397.2 °C and T90 = 463.2 °C) and nanoscale loading uniformity. Controlling the gas flow rate at 1 L/min can achieve the 21.56% thermal efficiency and 99.90% combustion efficiency. The heater can be preheated successfully at 120 °C and its cold start limitation is −30 °C. The infrared energy peak wavelength range (3–10 μm) is matched to the absorption ranges of the human skin and common textiles. Besides, real-person heating was tested in the apparent temperature (AT) region of −14.8–12.4 °C. Subjects' skin temperatures, subjective thermal sensations, and optimization suggestions were collected, and the relationship between mean skin temperature and AT was modeled, which revealed the efficient heating capacity. Therefore, this paper opens up great prospects for practical emergency heating and evaluation method for alleviating the cold-stricken heating problems.

Exploring the Predictive Potential of Physiological Measures of Human Thermal Strain in Outdoor Environments in Hot and Humid Areas in Summer-A Case Study of Shanghai, China.

Whenever people spend time outdoors during hot weather, they are putting themselves in potentially stressful situations. Being able to predict whether a person is overheating can be critical in preventing heat-health issues. There is a clear relationship between body core temperature and heat health. However, measuring body core temperature is expensive. Identifying a non-invasive measure that could indicate a person's thermal strain would be valuable. This study investigated five physiological measures as possible surrogates: finger mean skin temperature (FSKT), finger maximum skin temperature (FMSKT), skin conductance level (SCL), heart rate (HR), and heart rate variability (HRV). Furthermore, they were compared against the results of participants' subjective thermal sensation and thermal comfort in a range of hot microclimatic conditions in a hot and humid climate. Results showed that except for SCL, each of the other four physiological measures had a positive significant relationship with thermal sensation, but a negative relationship with thermal comfort. Furthermore, through testing by cumulative link mixed models, HRV was found to be the most suitable surrogate for predicting thermal sensation and thermal comfort through a simple, non-invasive measure in outdoor environment in summer in a hot and humid area. This study highlights the method for predicting human thermal strain and contributes to improve the public health and well-being of urban dwellers in outdoor environments.

Ergonomic evaluation of thermal comfort for different outlet distribution patterns and ventilation conditions in the pilot protective helmet

Ergonomic evaluation of thermal comfort is critical for heat stress alleviation systems in the pilot protective helmet, which is few investigated by existing approaches. In this study, CFD simulation under three ventilation pressure differences (60, 160, 260 Pa) and 4 outlet distribution patterns (ODP) was performed. Participants (n = 10) wearing the pilot protective helmet with a ventilation system were exposed to a constant thermal environment, while head skin temperature, subjective thermal sensation and comfort scales and relative humidity were measured. In simulation, head skin temperature changed oppositely to ventilation air pressure differences and increased due to the electronic module. Mean and maximum head skin temperatures were lower under ODP B and D. In experiments, head skin temperature was significantly lower after ventilation of 4 ODPs, while ODP B served optimal cooling effect. This study adds to the existing literature on head thermal comfort evaluation by extending the testing parameters and improving the testing accuracy.

Thermal comfort prediction considering thermal adaptation based on facial temperature using thermal images and subjective indexes

The aim of this study is to predict thermal comfort based on a subjective evaluation index of occupants and thermal imaging data, which are physiological signals, while considering thermal adaptation. This study was conducted in an office in the winter, and three subjective evaluation indexes were used. Air temperature data was obtained using a specific equipment, and the facial temperature was recorded using a thermal imaging camera. Based on analysis, thermal adaptation yielded different results at the same facial temperature. In previous studies, a facial temperature of 33 °C before thermal adaptation signified discomfort. However, the same facial temperature of 33 °C after thermal adaptation signified comfort. This implies that simple indexes and physiological signals based on thermal imaging are insufficient to predict the subjective thermal sensation of occupants. Therefore, accuracy of thermal comfort prediction can be improved significantly by considering thermal adaptation using the existing subjective evaluation indexes as well as by considering the results of studies pertaining to facial temperature.

Analysis of Heat and Moisture Transfer and Thermal Comfort in Green Logistics Storage Space

Regular logistics storage spaces suffer a very high temperature during summer. To build a green logistics storage space, it is truly necessary to optimize the thermal environment in summer. At present, there are few related studies on the energy consumption, thermal environment and human comfort of green logistics storage spaces. Therefore, this paper analyzes the heat and moisture transfer in and studies the impacts of the thermal environment of green logistics storage space. Based on the survey results, a coupled heat-moisture transfer model of green logistics storage space was constructed, which consists of three parts - the envelope structure, the hot and humid indoor environment, and the heating, ventilation and air conditioning (HVAC) system. Based on the idea of linear regression, a model was established to predict human body’s subjective thermal sensation in green logistics storage space. The experiment showed the analysis results of heat and moisture transfer and thermal comfort in green logistics storage space, and verified the effectiveness of the proposed model.

Research on the influence of indoor thermal environment and activity levels on thermal comfort in protective clothing

With the outbreak of infectious diseases such as Corona Virus Disease 2019, medical staff work intensively in isolated plots, medical disposable protective clothing (MDPC) has poor air condition and humidity permeability, which seriously reduces the thermal comfort of medical staff. In this paper, the effect of indoor thermal environment and activity levels on thermal comfort inside MDPC was studied by experiment. Five parts of the body were measured inside MDPC and the appropriate movements were chosen to simulate different levels of labor intensity. Meanwhile, physiological parameters and subjective thermal sensation were statistically analyzed. The results showed the influence range of different indoor temperatures on the temperature and humidity inside MDPC was about 1 °C and 10 %, respectively; it indicated that the environment inside MDPC could be improved by reducing indoor temperature, that is, a cross intelligent adjustment mode was proposed. The effect of labor intensity on the temperature inside MDPC was significantly less than that of humidity. Within 20 min, the humidity changes under moderate and heavy labor intensity were even more than 10 %, and the subjective discomfort threshold of the subjects increased by nearly 50 %. Furthermore, the maximum benefit could be obtained by concentrating cooling on back, forehead, chest and upper arm. Theoretical models of working time, labor intensity, and temperature and humidity inside MDPC under different indoor temperatures and different parts were given. In addition, acceptable regions inside MDPC which were approximately parallelogram in the enthalpy-humidity chart. These conclusions could be a reference for future thermal comfort inside MDPC research.

Study on indoor adaptive thermal comfort evaluation method for buildings integrated with semi-transparent photovoltaic window

Semi-Transparent Photovoltaic (STPV) windows have the potential of active energy-saving and have attracted more attention in recent years. Due to the selective absorption effect of solar cells on solar radiation, the indoor thermal environment and human thermal comfort of buildings integrated with STPV windows are considerably different from that with clear glass windows, and there are few studies on this. In this paper, the indoor human thermal comfort of buildings integrated with STPV window was investigated. Firstly, experiments and subjective questionnaires for the indoor environment were conducted in STPV and clear glass window buildings respectively. Secondly, the influence of illuminance on thermal sensation was statistically analyzed, with the consideration of visual effect, non-visual effect, as well as visual and non-visual coupling effect respectively. On this basis, an innovative thermal comfort evaluation method was provided. The thermo-physiological effect, light-physiological effect and light-psychological effect were comprehensively considered in this method. Finally, the reliability was verified by comparing with TSV. According to tests and questionnaires, it was found that the indoor thermal environment of the STPV window was an uneven thermal environment, and the subjective thermal sensation was more inclined to be slightly warm. When investigating the effect of illuminance on thermal sensation considering visual and non-visual coupling effect, it was found that illuminance had a significant influence on thermal sensation in different illuminance ranges. Meanwhile, it indicated the coupled effect of thermal environment and daylight environment on the thermal comfort of human.