Subjective Thermal Comfort Research Articles

Combined effects of Thermal-PM2.5 indicators on subjective evaluation of campus environment

This paper selects six typical spaces of a university campus in Xi'an to study the comprehensive effect of heat and PM2.5 in open spaces. Subjects are required to complete a subjective perception questionnaire in a thermal-PM2.5 interactive environment combined with on-site actual measurement. The results are shown in three aspects: (1) PM2.5 has a significant effect on thermal sensation and thermal comfort in the afternoon. PM2.5 concentration of 0–20 and 20–40 μg/m³ aggravates heat sensation of the crowd in summer and reduces subjective thermal comfort. (2) At constant physiological equivalent temperature (PET), air quality comfort decreases with increase in PM2.5 concentration. Generally, PM2.5 is 20–27, 20–23, and 20–24 μg/m³ in the morning, afternoon, and evening, respectively. People are more sensitive to the air quality with the increase of PET as the quality of comfort gradually improved. (3) Further, when PM2.5 concentration decreased from 20 to 40 to 0–20 μg/m³ at night, the mean value of overall comfort vote (OCV) increased by 0.46. Therefore, this paper can provide experimental support for establishing a human thermal comfort research system under the interaction of multiple environments, and can also provide a strategic basis for improving the urban outdoor thermal environment and air quality.

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.

Using machine learning algorithms to multidimensional analysis of subjective thermal comfort in a library

The thermal comfort in public buildings is affected by multiple psychological and physical factors. A deep understanding of these factors is necessary for intelligent ventilation control and architectural design. In this study, it was quantified the physiological and psychological parameters of the occupants in a library situated in Changsha using a questionnaire. Then, with the use of Principal Component Analysis (PCA), the dimensionality of the database was reduced. We found that the Zero-mean and unit variance projection is better than the Zero-mean projection, and 43-dimensional data can replace more than 90% of the original 61-dimensional data. Machine learning algorithms were used to analyze the results after PCA, which showed that the effect of thermal comfort on emotions is greater than that of emotions on thermal comfort. In addition, the performance of six machine learning algorithms (Linear Regression (LR), Linear Discriminant Analysis (LDA), K-Nearest Neighbors (KNN), Classification and Regression Trees (CART), Gaussian Naive Bayes (NB), and Support Vector Machine (SVM)) were compared. It is found that the predicted results of LDA were more accurate, and other algorithms showed different performances in different cases. These findings can contribute to the study of the subjective and objective feelings of indoor thermal comfort in public buildings, thereby guiding architectural design, intelligent control of ventilation systems, and realizing human-building interaction interfaces.

Combined effects of visual-acoustic-thermal comfort in campus open spaces: A pilot study in China's cold region

To investigate the combined effects of thermal, acoustic and visual comfort in open spaces, this study selected five typical spaces on a university campus with five common sounds (broadcasting music, running water & birdsong, wind (a gentle breeze) & insects, crowds, and machines) in a cold region of China. 418 volunteers were asked to complete a subjective sensory questionnaire in a randomly combined audio-visual environment while meteorological measures were taken on-site. Four primary outcomes emerged. First, broadcasting music improved individual subjective thermal comfort votes (TCV). Under the moderate heat stress (0.5 ≤ thermal sensation vote [TSV] ＜ 2.5), a comfortable acoustic environment helped reduce individuals' subjective TSV and increase TCV. Second, the subjective acoustic comfort vote (ACV) of broadcasting music, wind & insect sound and machine noise decreased with the increase of Universal Thermal Climate Index (UTCI); respondents perceived crowds, machines and wind & insects louder when TCV = 2 and −2. Third, under no thermal stress (−0.5 ≤ TSV ＜ 0.5)/moderate heat stress (0.5 ≤ TSV ＜ 2.5), TSV increased with increasing illumination intensity (LUX). Under the strong heat stress (2.5 ≤ TSV ≤ 3), there was no significant difference in TCV among subjective visual comfort vote (VCV) levels. Finally, when the LUX class was neutral/slightly bright, respondents felt darker in thermo-neutrality. Additionally, VCV and TCV were positively correlated under each LUX class.

Work strain and thermophysiological responses in Norwegian fish farming - a field study.

Fish farming is considered as a physical demanding occupation, including work operations with high workloads and awkward work positions for prolonged periods of time. Combined with potential challenging environmental conditions, these factors may negatively affect work performance, comfort and health. This study aimed to explore work strain and thermophysiological responses in Norwegian fish farming. Fourteen workers (age 35 ± 15 yrs) from four fish farms participated in the field studies, and measurements of heart rate (HR), core- and skin temperatures were registered continuously during a work shift. Questions about subjective thermal sensation and comfort were answered. This study has shown that workers at fish farms are periodically exposed to high or low levels of work strain, where the high workloads are manifested as increased core temperature and HR when working. The results are expected to give a better understanding of work strain and environmental challenges during fish farm operations.

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.

Assessing local heat stress and air quality with the use of remote sensing and pedestrian perception in urban microclimate simulations

Cities are increasingly confronted with multiple environmental and climatic stressors. Especially during heatwaves, street canyons are both producers and sufferers of air pollution and urban heat island (UHI) effects, with severe risks on public health. To better design mitigation measures, it is important to consider both the microclimate behaviors as well as the perceptions of the local population. Therefore, this study examined pedestrian perceptions and microclimate modelings to understand outdoor thermal comfort conditions and air pollution dispersion in the case study neighborhood of Dortmund Marten, Germany. A field survey with measurement points at two street canyons for climatic variables and questionnaires on subjective thermal comfort and air pollution was conducted on a hot day during the heatwave period in August 2020. As a cost-effective method for modeling input generation, we extracted spatial and spectral data like albedo, roof materials and tree locations out of remote sensing imageries. Finally, we compared the modeling results of the physiological equivalent temperature (PET) index, particulate matter concentrations and air temperatures with empirical field measurement data and the questionnaire responses. Results indicate that during hot summer days with light winds from the east, the north-south orientated street canyon with tree arrangements tends to act as a tunnel for particulate matter accumulation. Coincidently, pedestrians show less thermal discomfort than calculated PET values in that particular area during morning and daytime, which underlines the dichotomy of such places. On the other hand, the low rise east-west orientated street canyon shows higher PET votes than predicted by the model. However, particulate matter concentrations were considerably underestimated by the model, while air temperature predictions provided meaningful results. The proposed workflow shows the potential to accelerate future preparations of input data for microclimate modelings, while the results can enhance wind-sensitive planning procedures and heat stress resilience in mid-latitude urban neighborhoods.

Human cognitive functions and psycho-physiological responses under low thermal conditions in a simulated office environment.

In office environments, thermal comfort is one of the most significant factor affecting employees' performance. This study aimed to determine the effects of exposure to low air temperatures on human cognitive performance, physiological responses, and thermal perceptions during mental work. Twenty-four volunteers with an age range of 18-30 years participated in this study. The subjects were exposed to four different air temperatures (10, 14, 18, and 22°C) in a climate chamber based on a within-subject design. The n-back, CPT, and PVT tests were employed to evaluate some basic aspects of cognitive performance. Body physiological responses and the subjective thermal comfort were also measured. When the thermal condition deviated from relatively neutral temperature, the subjects' cognitive responses significantly disturbed (P < 0.05), such that the response accuracy was more affected by reduction of air temperature. The blood pressures and heart rate, galvanic skin response, and respiration rate increased as the air temperature decreased (P < 0.05), such that the galvanic skin response as a stress indicator was more affected. In the test configurations, as a result of decrease in air temperature of 1°C, the finger and body skin temperatures reduced to 0.74°C and 0.25°C, respectively. The findings confirmed that low thermal condition can considerably affect cognitive performance and physiological responses during some office work tasks. The subjects' thermal comfort votes proposed that air temperature lower than 14 °C can be intolerable for employees during routine mental work. It is suggested that personalized conditioning systems should be used to provide individual thermal comfort in moderate cold air conditions.

Remotely Sensed Derived Land Surface Temperature (LST) as a Proxy for Air Temperature and Thermal Comfort at a Small Geographical Scale

Urban Heat Islands (UHIs) and Urban Cool Islands (UCIs) can be measured by means of in situ measurements and interpolation methods, which often require densely distributed networks of sensors and can be time-consuming, expensive and in many cases infeasible. The use of satellite data to estimate Land Surface Temperature (LST) and spectral indices such as the Normalized Difference Vegetation Index (NDVI) has emerged in the last decade as a promising technique to map Surface Urban Heat Islands (SUHIs), primarily at large geographical scales. Furthermore, thermal comfort, the subjective perception and experience of humans of micro-climates, is also an important component of UHIs. It remains unanswered whether LST can be used to predict thermal comfort. The objective of this study is to evaluate the accuracy of remotely sensed data, including a derived LST, at a small geographical scale, in the case study of King Abdulaziz University (KAU) campus (Jeddah, Saudi Arabia) and four surrounding neighborhoods. We evaluate the potential use of LST estimates as proxy for air temperature (Tair) and thermal comfort. We estimate LST based on Landsat-8 measurements, Tair and other climatological parameters by means of in situ measurements and subjective thermal comfort by means of a Physiological Equivalent Temperature (PET) model. We find a significant correlation (r = 0.45, p &lt; 0.001) between LST and mean Tair and the compatibility of LST and Tair as equivalent measures using Bland-Altman analysis. We evaluate several models with LST, NDVI, and Normalized Difference Built-up Index (NDBI) as data inputs to proxy Tair and find that they achieve error rates across metrics that are two orders of magnitude below that of a comparison with LST and Tair alone. We also find that, using only remotely sensed data, including LST, NDVI, and NDBI, random forest classifiers can detect sites with “very hot” classification of thermal comfort nearly as effectively as estimates using in situ data, with one such model attaining an F1 score of 0.65. This study demonstrates the potential use of remotely sensed measurements to infer the Physiological Equivalent Temperature (PET) and subjective thermal comfort at small geographical scales as well as the impacts of land cover and land use characteristics on UHI and UCI. Such insights are fundamental for sustainable urban planning and would contribute enormously to urban planning that considers people’s well-being and comfort.

Thermal comfort interventions of landscape elements in a humid and subtropical residential area in China

ABSTRACT This study aimed at revealing the subjective thermal comfort intervention of landscape elements in the humid and subtropical residential area of China. Data based on physical measurements and questionnaire surveys were collected. A new empirical model was developed according to microclimatic and subjective criteria, which considers air temperature, solar radiation, and wind speed. According to the empirical model in summer, a decrease of 84 W/m2 in global radiation or an increase of 0.35 m/s in wind speed would have the same effects on thermal perception as a drop of 1 °C in air temperature. A similar analysis could be conducted with the winter model, a change of 20 W/m2 in global radiation or a change of 0.10 m/s in wind speed have the same effects as a change of 1 °C in air temperature. Furthermore, the thermal comfort intervention of tree, shrubs, reflective surface and pervious ground were quantitatively analyzed based on the empirical model. We proposed that large broad-leaved trees and pervious ground were more conducive to the improvement of thermal acceptability during different seasons. The results showed that in summer, the total acceptable area significantly increased by 38.5%, whereas it was slightly reduced by 8.4% in winter.

Evaluating outdoor thermal comfort in “Haats” – The open air markets in a humid subtropical region

This study deals with outdoor thermal comfort assessment in two designed open-air markets – “Haats” in New Delhi, India. The study evaluates the impact of physical and subjective attributes on outdoor thermal comfort in this unique spatial typology. The field surveys comprise of micrometeorological measurements at seventeen locations accompanied by subjective thermal comfort surveys with 392 visitors. Physiological Effective Temperature (PET) and Mean radiant temperature (Tmrt) are computed from the measured variables. The neutral value of PET is found to be 24.7 °C. A significant difference in neutral PET prevail between the two Haats. This is attributed to environmental stimuli as well as presence of adaptive opportunities. Variables such as purpose of visit, gender and kinetic state of the respondents play a decisive role in influencing thermal sensation and acceptability. Design attributes of the Haats such as landscape elements, luminous environment and perceived color sensation of material palette significantly influence the thermal perception.

Physiological and subjective thermal responses to heat exposure in northern and southern Chinese people

When studying the thermal adaptation of building occupants, understanding the effects of different thermal experiences on adaptation is necessary, particularly for moderate and severe heat exposure. However, this area has seen limited research. Further, skin temperature, a common parameter for quantifying thermal sensation, may insufficiently reflect the automatic thermoregulation of the human body. This study investigates the effects of long-term heat exposure on the human body using multiple physiological and subjective indexes. Two heat exposure experiments were conducted on healthy male participants from northern and southern China. Participant responses, including skin temperature, heart rate, heart rate variability, blood volume pulse (BVP), subjective thermal comfort, thermal sensation, thermal acceptability, and normalized high and low frequency values were collected and compared. The results indicated that the subjective responses of northern and southern participants were not significantly different; however, the subjective physiological symptoms and self-reported discomfort of the latter were less than those of the former, indicating that the southern participants had superior heat tolerance. Additionally, the physiological responses of all the participants were largely similar. However, southern participants showed slightly higher normalized high frequency and BVP values, indicating that they have more active vagus nerves and better vasodilation. They also showed a wider acceptable temperature range and better acclimation to heat exposure. Notably, the mean skin temperature could not effectively predict thermal sensation during heat exposure; this was more accurately achieved using the rate of change of skin temperature. These findings suggest that long-term thermal experiences can affect building occupants’ thermal adaptability.

A Behavioural Analysis of Outdoor Thermal Comfort: A Comparative Analysis between Formal and Informal Shading Practices in Urban Sites

This study calls for the integration of context-based socio-cultural habits and learning from local practices in providing outdoor thermal comfort in conservation areas. These parameters have direct impacts on outdoor activities, especially in hot arid climates. The study took place in two nearby locations one renovated and all external shadings removed to provide visual vistas to monuments while on the same street, no more than 1500 m apart, local shading practices were left in places. Sun-exposed as opposed to shaded sites were compared for subjective thermal comfort and outdoor activity, via structured interviews, observations, and wide-ranging micrometeorological measurements. The aim was to investigate psychological factors, including overall thermal comfort and perception, in addition to environmental parameters, such as solar radiation intensity and thermal adaptation. The analysis illustrates the importance of shading as a dominant factor in achieving thermal comfort on the urban scale, with a neutral temperature in summer of 29.9 °C and 29.2 °C for shaded and sun-exposed locations, respectively. The results suggest people may be more willing to tolerate higher temperatures in shaded rather than sun-exposed locations. Moreover, cultural constraints and context-based behaviour proved to have some influences on people’s levels of adaptation and their thermal behaviour.

Thermal comfort and physiological responses with standing and treadmill workstations in summer

The study investigates human thermal comfort requirements when using standing and treadmill workstations. Twenty-eight subjects were exposed to four ambient temperatures (20, 23, 26, 29 °C) while conducting four activities (sitting, standing, walking at 1.0 km/h, and walking at 2.0 km/h). Physiological responses, including metabolic rate, skin temperature, and skin wettedness, were measured continuously, while subjective thermal comfort responses were surveyed. Treadmill workstation significantly increased human metabolic levels and reduced the associated environmental neutral temperatures. Using linear regressions, the predicted neutral temperatures are 24.3 °C (sitting), 23.3 (standing), 22.2 (walking 1 km/h), and 21.1 °C (walking 2 km/h), respectively. The 80% acceptable temperature range varied from 20.5 to 28.2 °C for sitting and standing, 20.0–26.9 °C for walking 1 km/h, and 17.6–26 °C for walking 2 km/h. PMV-PPD model was not able to predict human comfort accurately when using standing or treadmill workstations. Based on our findings, a temperature zone ranging from 20.5 to 26 °C is seen to satisfy the summer thermal requirements for over 80% occupants in a space containing a combination of sitting, standing, and treadmill workstations. However, providing personal comfort control would be necessary, given the substantial inter-individual differences.

Thermal comfort under weightlessness: A physiological prediction

This study investigated the physiological thermal response of people under simulated weightlessness using a 6° head down bed rest (HDBR) model to ensure the human body functions in the weightlessness way. Thermal responses of six male participants were experimentally determined. The relationship between thermal comfort and heart rate variability (HRV) was also scrutinized. Physiological responses of participants under different environmental conditions were observed including core temperature, sweating, and most importantly, HRV. Elevated core temperatures were observed amongst participants, with a maximum increment of 0.5°C. The sweating of participants under simulated weightlessness was conspicuously retarded, requiring a 2–4°C increase in environmental temperature to start sweating. Body regional differences in the sweating were also observed. The HRV index ‘LF/HF’, which reflects the balance of the autonomous nervous system, was found to vary with the environment and closely associated with the variation in the thermal comfort scores. Participants under simulated weightlessness had higher mean LF/HF when they felt comfortable, and they preferred a warmer environment in comparison to under normal gravity condition. An altered thermoregulation of the human body under simulated weightlessness was indicated by our findings. The use of HRV index could provide a useful prediction of subjective thermal comfort under weightlessness.

Influence of long-term thermal history on thermal comfort and preference

This study explores how climatic background or long-term thermal history influences individuals’ in-the-moment thermal comfort experiences. This investigation was conducted at eight mixed-mode university buildings in United Kingdom whose occupants had diverse thermal histories. The research design consisted of simultaneous environmental measurements, a questionnaire survey and observation on 3,452 students performing sedentary activities in the classrooms. To eliminate the influence of acclimatisation in the UK, a subset of 1,225 students with less than 3 years of residence in the UK were selected as the survey sample. Students’ thermal comfort responses were categorised into three main groups based on their climatic background compared to the UK (warmer, similar and cooler climatic background groups). Data was statistically analysed to derive the thermal comfort requirements of each climatic group based on reported thermal sensations, preferences, acceptability and comfort votes. The findings confirm the influence of long-term thermal history on thermal sensation, thermal comfort zone, acceptability, preference and comfort temperature (neutrality). There was generally no difference in the subjective thermal comfort of the students with similar climatic backgrounds to the UK and those from cooler climates than the UK. However, significant differences appeared between the warmer thermal history group and the other two groups. It was also demonstrated that the participants with a warmer thermal history had cooler thermal sensations compared to their counterparts in the similar-to and colder-than-UK thermal history groups, when exposed to the same environments. The optimal acceptable temperature was higher for the warmer climatic background (24 °C) than the similar/cooler climatic background groups (22 °C). Likewise, heightened values of preference and comfort temperatures were observed for the warmer thermal history group than the other two groups, despite their heavier clothing insulation than the other groups.

Dimension analysis of subjective thermal comfort metrics based on ASHRAE Global Thermal Comfort Database using machine learning

We analyzed the ASHRAE Global Thermal Comfort Database II to answer a fundamental but overlooked question in thermal comfort studies: how many and which subjective metrics should be used for the assessment of the occupants' thermal experience. We found that the thermal sensation is the most frequently used metrics in Thermal Comfort Database II, followed by thermal preference, comfort and acceptability. The thermal sensation/thermal preference, thermal comfort/air movement acceptability and thermal comfort/thermal preference are the top three most dependent metrics pairs. A principal component analysis confirmed that the personal experience of thermal conditions in built environment is not a one-dimensional problem, but at least a two-dimensional problem, and suggested thermal sensation and thermal comfort should be asked in right-now surveys as the first two Principal Component are majorly constructed by thermal sensation and thermal comfort. To further confirm the predictive power of thermal sensation and comfort, we used logistic regression and support vector machine to predict thermal acceptability and thermal preference with thermal sensation and comfort. The prediction accuracy is 87% for thermal acceptability and 64% for thermal preference. The prediction error might be due to occupants' individual difference and people errors in answering survey. These findings could help the design of chamber experiments, field studies, and human-building interaction interfaces by shedding light on the choice of subjective thermal metrics to effectively and accurately collect information on occupants’ thermal experience.

A study on the summer thermal comfort and behaviour patterns in the residential buildings of Kashgar old City, China

Kashgar, located in China’s far west, has a typical hot-arid climate. There are a large number of low-rise high-density Islamic housing in Kashgar old City. The thermal comfort in these buildings has not yet been adequately researched. In order to obtain a comprehensive understanding about the real indoor thermal environment and the residents’ summer thermal comfort in Kashgar old City, a field investigation of 138 residential buildings was conducted in the summer time, including onsite environmental parameter measurements and simultaneous surveys using subjective thermal comfort questionnaires. Based on a statistical regression analysis of 182 valid questionnaires, a summer thermal comfort model was established. The results show that the measured summer neutral temperature of the local people is 23.4°C, and the upper limit of acceptable summer temperature for 80% of the residents is 26.9°C. The summer thermal tolerance of the residents in the Kashgar old City is lower than expected and also lower than that of the residents in rural Turpan with the same climate features. The survey also shows that the residents in the Kashgar old City have a habit of transfering living spaces over time, and the frequency of passive behaviours is higher than those of active behaviours. The above results are believed to be potentially valuable for the revision of energy conservation policies and the design practice of residential buildings in the hot-arid climate region of China, and also for areas under similar climate conditions in the world.

Comparison of local equivalent temperatures and subjective thermal comfort ratings with regard to passenger comfort in a train compartment

Two methods for assessing thermal passenger comfort are analysed and compared to each other in terms of different ventilation concepts and different inflow air temperatures in a generic train laboratory. The studied ventilation systems comprise state-of-the-art micro-jet ventilation and a novel vertical ventilation system called displacement ventilation. The latter is based on a homogeneous and low-momentum air supply near the floor. In a first step, tests with human subjects are conducted addressing both temperature sensation and evaluation. In a second step, objective thermal comfort parameters are acquired using a calibrated thermal manikin, which enables the measurement of local equivalent temperatures. For reason of comparability, the results of the subjects test are converted into equivalent temperatures. The results prove that both methods, subjective and objective, correspond well under steady-state thermal conditions. The data of the subject tests are characterized by significantly higher variations compared to the experimentally determined values. Concerning the overall thermal comfort, both ventilation systems show comparable results for the two investigated inflow air temperatures. However, the comfort distribution over the body parts differs significantly between the two ventilation concepts.

A thermal comfort environmental chamber study of older and younger people

We investigated whether or not, when exposed to the same conditions, older people (those aged 65 and over) had different thermal sensations, comfort, acceptability and preferences from their younger counterparts. The study was conducted in a thermal comfort environmental chamber, involving 22 older (average 69.7 years old) and 20 younger (29.6 years old) subjects, exposed to four test conditions between slightly cool and slightly warm. Subjective thermal comfort perceptions for local body parts and whole-body were surveyed. Skin temperatures were measured at four body locations: neck, right scapula, left hand, and right shin. We also investigated the correlation between the frailty level of the subjects and their thermal comfort levels. The study found no significant difference between the thermal sensation, comfort and acceptability of older and younger subjects. We also found no correlation between subjects' frailty level and their thermal sensation, comfort, acceptability and preference but we did not have many frail subjects. In both older and younger subjects, the hand's skin temperature had a significant correlation with the local and overall thermal sensation.