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Regulation of indoor temperature based on neurophysiological and psychological signals is one of the most promising technologies for intelligent buildings. In this study, we developed a system for closed-loop control of indoor temperature based on brain-computer interface (BCI) technology for the first time. Electroencephalogram (EEG) signals were collected from subjects for two room temperature categories (cool comfortable and hot uncomfortable) and used to build a thermal-sensation discrimination model (TSDM) with an ensemble learning method. Then, an online BCI system was developed based on the TSDM. In the online room temperature control experiment, when the TSDM detected that the subjects felt hot and uncomfortable, BCI would automatically turn on the air conditioner, and when the TSDM detected that the subjects felt cool and comfortable, BCI would automatically turn off the air conditioner. The results of online experiments in a hot environment showed that a BCI could significantly improve the thermal comfort of subjects (the subjective thermal comfort score decreased from 2.45 (hot uncomfortable) to 0.55 (cool comfortable), p 0.001). A parallel experiment further showed that if the subjects wore thicker clothes during the experiment, the BCI would turn on the air conditioner for a longer time to ensure the thermal comfort of the subjects. This has further confirmed the effectiveness of TSDM model in evaluating thermal sensation under the dynamic change of room temperature and showed the model's good robustness. This study proposed a new paradigm of human-building interaction, which is expected to play a promising role in the development of human-centered intelligent buildings.

Indoor air quality (IAQ) in classrooms has a significant impact on children's academic performance, health, and well-being; therefore, understanding children's perception of IAQ is vital. This study investigates how children's perception of IAQ is affected by environmental variables and thermal sensation. In total, 29 naturally ventilated classrooms in eight UK primary schools were selected and 805 children were surveyed during non-heating and heating seasons. Results show that air sensation votes (ASVs) are more correlated to CO2 levels than to operative temperatures (Top ) during non-heating seasons and more correlated to Top than CO2 levels during heating seasons. The impact of Top on ASVs decreases with an increase in CO2 levels, and the effect of CO2 levels on ASVs decreases with increase in Top . The most favorable ASVs are given when children feel "cool" and have "as it is" preference. By keeping CO2

Recently, studies suggest that the average indoor temperature is typically >30°C and that the maximum temperature can reach 37.5°C in hot-humid areas. However, the effects caused by increasing the humidity at high indoor temperatures are not clear. In this study, twelve female and twelve male subjects were exposed to different operative temperature (26.6, 30.6, and 37.4°C) and relative humidity (50% and 70%) in a climate chamber. Data concerning thermal sensation, perceived air quality, and Sick Building Syndrome (SBS) were collected during 190-min-long exposure to each thermal condition. Heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature were measured. It was found that increasing the relative humidity from 50% to 70% at 26 and 30°C had no significant effects on the physiological responses, thermal comfort, perceived air quality, or SBS symptoms of the subjects. However, when the temperature was elevated to 37°C, the heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature increased significantly as a result of the increase in the relative humidity from 50% to 70%. The subjects felt hotter and more uncomfortable, and they found indoor air quality was more difficult to accept. The subjects are acclimatized to hot environments and more tolerant to heat. Therefore, the results are applicable to the acclimated people living in hot-humid climate.

Thermal adaptations, as feedbacks of occupants to physical stimuli, extend thermal comfort zone thereby reducing building energy consumption effectively. The rational approach models thermal comfort from the perspective of the body's heat balance, but is limited in explaining the thermal adaptations. The adaptive approach of modeling thermal comfort can fully account for the thermal adaptations, but ignores the body's heat balance. To improve thermal comfort prediction, this study proposes an adaptive-rational thermal comfort model, that is, an adaptive predicted mean vote with a variable adaptive coefficient (termed as arPMV). By linearly linking the negative feedback effects of the thermal adaptations to the ambient temperature according to the adaptive approach, the variable adaptive coefficient is linearly related to the reciprocal of the ambient temperature with two constants. The variable adaptive coefficient is determined by explicitly quantifying the two constants as the functions of the predicted mean vote, thermal sensation vote, and ambient temperature. The proposed arPMV is validated for naturally ventilated, air-conditioned, and mixed-mode buildings, with the mean absolute error and the robustness of the thermal sensation prediction reduced by 24.8%-83.5% and improved by 49.7%-83.4%, respectively.

Indoor air 32(3), e13018 (2022). doi:10.1111/ina.13018, Published by Wiley-Blackwell, Oxford

In the hot climate of Saudi Arabia, people living year-round in air-conditioned spaces are likely to develop high expectations for homogeneity and cool temperatures, becoming potentially more sensitive if thermal conditions deviate from the comfort zone they expect. This paper presents the results from a field intervention investigating the association between participants’ thermal sensations with cognitive performance in a female university in Saudi Arabia. The climatic context plays a key role in choosing Saudi Arabia, whereas the total reliance on air-conditioners (AC) for cooling is believed to have significant effects on occupants’ perceptions of the comfort temperature. Results reveal discrepancies in the actual thermal sensations between the Saudi and non-Saudi participants which affected their performances. “Cool” and “Slightly Cool” sensations versus neutral were associated with significant lower percentage of errors and significant higher speed for all participants independently of any association with ethnicity and acclimatization. The estimates remained significant even after adjusting for ethnicity and the number of years spent in the country and the set temperature of AC at home. Implications of the study suggest a preference for staying cool when working independently of acclimatization status.

The relation between electroencephalogram signals, thermal comfort, and cognitive performance in neutral to hot indoor environment was investigated. The experiments were carried out at four temperatures: 26ºC, 30ºC, 33ºC, and 37ºC, and two relative humidity levels: 50% and 70%. Thirty-two subjects were exposed for 175 min. The electroencephalogram signals were measured for 30 min 25 min after the onset of exposure while the recruited subjects performed neurobehavioral tests and rated their thermal comfort. The relative power of electroencephalogram signals has a significant correlation with thermal comfort and performance of neurobehavioral tests. The ratings of acceptability of thermal environment and thermal comfort, the speed, accuracy, and PI of completing the tests are negatively correlated with the relative power of δ-band, but positively correlated with θ-band, α-band, and β-band. The ratings of thermal sensation have a better correlation with the above four bands, but the correlation trend is opposite. A linear relation was found between electroencephalogram signals and the speed. The results showed that the relative power of P7 channel located in the occipital lobe is the most suitable as a single electroencephalogram channel to reflect joint thermal comfort and cognitive performance at high temperatures, especially its α-band.

Thermal comfort, self-reported acute health symptoms, cognitive performance, and physiological reactions were examined at four temperatures (26, 30, 33, and 37°C) at a relative humidity of 70%. Thirty-two sub-tropically acclimatized subjects experienced each condition for 175 minute, in balanced order, in a climatic chamber. The perception of heat gradually increased with increasing temperature, but the subjects felt hot only at 37°C. The temperature of 33°C was on average rated as acceptable and only just uncomfortable. The acceptability of air quality decreased linearly with increasing temperature. The intensity of acute health symptoms reported by the subjects increased with increasing temperature, but it was no more than moderate even at the highest temperature; dryness of skin and eye were alleviated. The eardrum temperature, skin temperature and moisture, heart rate, end-tidal carbon dioxide, and weight loss increased significantly with increasing temperature, whereas the percentage of adjacent heart inter-beat intervals differing by >50 ms decreased significantly. These results suggest that the perceived heat, self-reported symptoms, and physiological reactions occurred concurrently. They show additionally that acclimatization to heat may shift the boundary of thermal discomfort to a higher temperature. The role of psychological adaptation and of the contextual aspects of this process still requires clarification in future experiments.

Thermal pleasure is currently measured along psychological and physiological variables. However, in transient environments where temperatures change, it is hard to correlate psychological and physiological measures, because there is a delay in physiological changes. This study tests a method for correlating both measures using electroencephalogram (EEG), which can capture physiological feedback with a rapid response rate. In this experimental study, thermal pleasure was induced in a temperature step-change environment, one of non-uniform and transient environments. During the experiment, EEG was monitored and psychological responses of thermal sensation and thermal comfort votes were collected via survey questionnaire. A total of 50 males in their twenties participated in a climate chamber experiment. An experimental group of 25 men were exposed to temperature step-change between two different room conditions (32°C, 65% and 25°C, 50%), experiencing thermal pleasure. The control group of the remaining 25 men were exposed to an unchanging condition, experiencing thermal comfort close to thermal neutrality. The EEG spectral analysis demonstrated that EEG frequency band associated with pleasant emotional (theta) increased while frequency band related to pleasantness, satisfaction or relaxation (beta) decreased with thermal pleasure.

This study aims to develop an approach to couple a computational fluid dynamics (CFD) solver to the University of California, Berkeley (UCB) thermal comfort model to accurately evaluate thermal comfort. The coupling was made using an iterative JavaScript to automatically transfer data for each individual segment of the human body back and forth between the CFD solver and the UCB model until reaching convergence defined by a stopping criterion. The location from which data are transferred to the UCB model was determined using a new approach based on the temperature difference between subsequent points on the temperature profile curve in the vicinity of the body surface. This approach was used because the microclimate surrounding the human body differs in thickness depending on the body segment and the surrounding environment. To accurately simulate the thermal environment, the numerical model was validated beforehand using experimental data collected in a climate chamber equipped with a thermal manikin. Furthermore, an example of the practical implementations of this coupling is reported in this paper through radiant floor cooling simulation cases, in which overall and local thermal sensation and comfort were investigated using the coupled UCB model.

Predicted mean vote (PMV) is a prevailing thermal comfort model adopted by thermal comfort standards. To extend its ability in explaining thermal adaptations, the PMV is multiplied by an extension factor. However, the original extended PMV (ePMV) cannot account for thermal adaptations around thermal neutrality, resulting in deviation around thermal neutrality, therefore, is unable to predict thermal sensation around thermal neutrality accurately. Given the unusual importance of thermal sensation around thermal neutrality for energy-efficient provision of indoor thermal comfort, this study modifies the ePMV to reinforce thermal adaptations around thermal neutrality by adding a thermal neutrality factor. The modified ePMV is quantified by explicitly expressing the extension factor and the thermal neutrality factor as functions of field datasets of the PMV, thermal sensation vote (TSV), and ambient temperature. The modified ePMV is validated to improve thermal sensation prediction effectively (by up to 73%), particularly for prediction around thermal neutrality with the TSV between -0.5 and 0.5, by mitigating deviation around thermal neutrality for different types of buildings under various climate conditions around the world. Moreover, the modified ePMV is explicitly formulated and, therefore, convenient for practical applications.

In a warm and humid climate, increasing the temperature set point offers considerable energy benefits with low first costs. Elevated air movement generated by a personally controlled fan can compensate for the negative effects caused by an increased temperature set point. Fifty-six tropically acclimatized persons in common Singaporean office attire (0.7 clo) were exposed for 90 minutes to each of five conditions: 23, 26, and 29°C and in the latter two cases with and without occupant-controlled air movement. Relative humidity was maintained at 60%. We tested thermal comfort, perceived air quality, sick building syndrome symptoms, and cognitive performance. We found that thermal comfort, perceived air quality, and sick building syndrome symptoms are equal or better at 26°C and 29°C than at the common set point of 23°C if a personally controlled fan is available for use. The best cognitive performance (as indicated by task speed) was obtained at 26°C; at 29°C, the availability of an occupant-controlled fan partially mitigated the negative effect of the elevated temperature. The typical Singaporean indoor air temperature set point of 23°C yielded the lowest cognitive performance. An elevated set point in air-conditioned buildings augmented with personally controlled fans might yield benefits for reduced energy use and improved indoor environmental quality in tropical climates.

Thermal sensation models, capable of predicting human's perception of thermal surroundings, are commonly used to assess given indoor conditions. These models differ in many aspects, such as the number and type of input conditions, the range of conditions in which the models can be applied, and the complexity of equations. Moreover, the models are associated with various thermal sensation scales. In this study, a systematic comparison of seven existing thermal sensation models has been performed with regard to exposures including various air temperatures, clothing thermal insulation, and metabolic rate values after a careful investigation of the models' range of applicability. Thermo-physiological data needed as input for some of the models were obtained from a mathematical model for human physiological responses. The comparison showed differences between models' predictions for the analyzed conditions, mostly higher than typical intersubject differences in votes. Therefore, it can be concluded that the choice of model strongly influences the assessment of indoor spaces. The issue of comparing different thermal sensation scales has also been discussed.

We conducted a climate chamber study on the thermal comfort of people in the hot and humid area of China. Sixty subjects from naturally ventilated buildings and buildings with split air conditioners participated in the study, and identical experiments were conducted in a climate chamber in both summer and winter. Psychological and physiological responses were observed over a wide range of conditions, and the impacts of season, climate, and thermal history on human thermal comfort were analyzed. Seasonal and climatic heat acclimatization was confirmed, but they were found to have no significant impacts on human thermal sensation and comfort. The outdoor thermal history was much less important than the indoor thermal history in regard to human thermal sensation, and the indoor thermal history in all seasons of a year played a key role in shaping the subjects' sensations in a wide range of thermal conditions. A warmer indoor thermal history in warm seasons produced a higher neutral temperature, a lower thermal sensitivity, and lower thermal sensations in warm conditions. The comfort and acceptable conditions were identified for people in the hot and humid area of China.

The use of displacement ventilation for cooling environments is limited by the vertical temperature gradient. Current standards recommend a temperature difference of up to 3 K/m between the head and the feet. This paper reviews the scientific literature on the effect of vertical temperature gradients on thermal comfort and compares this to the results of our own experiments. Early experiments have demonstrated a high sensitivity of dissatisfied test subjects to changes in the temperature gradient between head and foot level. Recent studies have indicated that temperature gradients of 4-5 K/m are likely to be acceptable, and the mean room temperature may have a greater sensitivity on the percentage of dissatisfied (PD). In new experiments, test subjects have evaluated the thermal comfort of different vertical air temperature gradients in a modular test chamber, the Aachen comfort cube (ACCu), where they have assessed vertical temperature gradients of ΔT/Δy = 1, 4.5, 6, 8, and 12 K/m at a constant mean room temperature of 23°C. The results of the different temperature gradients are in contrast to ANSI/ASHRAE Standard 55 (Thermal Environmental Conditions for Human Occupancy, Atlanta GA, American Society of Heating, Refrigerating and Air Conditioning Engineers, 2013) as the PD increases almost constantly with higher vertical air temperature gradients. The PD for the overall sensation increases by approximately 7% between gradients of 1 and 8 K/m. The evaluation of our own tests has revealed that vertical temperature gradients of up to 8 K/m or higher are likely to be acceptable for test subjects.

At the University of Debrecen, a new method and equipment for personalized ventilation has been developed. This equipment makes it possible to change the airflow direction during operation with a time frequency chosen by the user. The developed office desk with integrated air ducts and control system permits ventilation with 100% outdoor air, 100% recirculated air, or a mix of outdoor and recirculated air in a relative proportion set by the user. It was shown that better comfort can be assured in hot environments if the fresh airflow direction is variable. Analyzing the time step of airflow direction changing, it was found that women prefer smaller time steps and their votes related to thermal comfort sensation are higher than men's votes.

Climate change and the urgency of decarbonizing the built environment are driving technological innovation in the way we deliver thermal comfort to occupants. These changes, in turn, seem to be setting the directions for contemporary thermal comfort research. This article presents a literature review of major changes, developments, and trends in the field of thermal comfort research over the last 20 years. One of the main paradigm shift was the fundamental conceptual reorientation that has taken place in thermal comfort thinking over the last 20 years; a shift away from the physically based determinism of Fanger’s comfort model toward the mainstream and acceptance of the adaptive comfort model. Another noticeable shift has been from the undesirable toward the desirable qualities of air movement. Additionally, sophisticated models covering the physics and physiology of the human body were developed, driven by the continuous challenge to model thermal comfort at the same anatomical resolution and to combine these localized signals into a coherent, global thermal perception. Finally, the demand for ever increasing building energy efficiency is pushing technological innovation in the way we deliver comfortable indoor environments. These trends, in turn, continue setting the directions for contemporary thermal comfort research for the next decades.

Neutral thermal sensation is expected for a human body in heat balance in near-steady-state thermal environments. The physiological thermoneutral zone (TNZ) is defined as the range of operative temperatures where the body can maintain such heat balance by actively adjusting body tissue insulation, but without regulatory increases in metabolic rate or sweating. These basic principles led to the hypothesis that thermal sensation relates to the operative temperature distance from the thermoneutral centroid (dTNZop). This hypothesis was confirmed by data from respiratory climate chamber experiments. This paper explores the potential of such biophysical model for the prediction of thermal sensation under increased contextual variance. Data (798 votes, 47 participants) from a controlled office environment were used to analyze the predictive performance of the dTNZop model. The results showed a similar relationship between dTNZop and thermal sensation between the dataset used here and the previously used dataset. The predictive performance had the same magnitude as that of the PMV model; however, potential benefits of using a biophysical model are discussed. In conclusion, these findings confirm the potential of the biophysical model with regard to the understanding and prediction of human thermal sensation. Further work remains to make benefit of its full potential.

Human thermal comfort researches mainly focus on the relation between the environmental factors (e.g. ambient temperature, air humidity, and air velocity, etc.) and the thermal comfort sensation based on a large amount of subjective field investigations. Although some physiological factors, such as skin temperature and metabolism were used in many thermal comfort models,they are not enough to establish a perfect thermal comfort model. In this paper,another two physiological factors, i.e. heart rate variation (HRV) and electroencephalograph (EEG), are explored for the thermal comfort study. Experiments were performed to investigate how these physiological factors respond to the environmental temperatures, and what is the relationship between HRV and EEG and thermal comfort. The experimental results indicate that HRV and EEG may be related to thermal comfort, and they may be useful to understand the mechanism of thermal comfort.

UNLABELLED Airflow fluctuation is an important factor affecting indoor thermal environments and human thermal response. In this study, dynamic airflows with different fluctuation characteristics were generated by a dynamic air supply terminal. The influence of three different kinds of airflows, constant airflow, simulated natural airflow and sinusoidal airflow, on thermal comfort was studied. Subjective experiments indicated that a dynamic airflow can cause a stronger cold sensation, and that air movement with 1/f fluctuations similar to natural wind is more acceptable than other dynamic airflows in warm environments. Moreover, the impact of draughts in dynamic airflows on human thermal response is different in neutral-warm (30 degrees C) and cool-neutral (26 degrees C) thermal environments. PRACTICAL IMPLICATIONS By means of a dynamic air supply terminal it is possible to generate artificial airflows that simulate natural wind indoors. This kind of airflow with higher velocity is more comfortable and causes less draught sensation than the constant airflows supplied by conventional fans. While the cooling effect of this airflow is utilized in the built environment, the design temperature of air-conditioning system can be increased and the amount of energy consumption can be reduced dramatically.

UNLABELLED This paper reviewed the CFD (Computational Fluid Dynamics) study conducted by our group on analyzing and designing the microclimate surrounding the human body. First, it describes the analysis results of flow and temperature fields around the human body. Next, it refers to the analysis and design of the quality of air inhaled and exhaled by the human body. Lastly, it describes the CFD and experimental study on the microclimate around the eyes, focusing on dry eye syndrome. PRACTICAL IMPLICATIONS The CFD method presented will be a valuable and powerful tool for analysis and design of healthy indoor environments.

UNLABELLED Computational Fluid Dynamics (CFD) and new developments of CFD in the indoor environment as well as quality considerations are important elements in the study of energy consumption, thermal comfort and indoor air quality in buildings. The paper discusses the quality level of Computational Fluid Dynamics and the involved schemes (first, second and third order schemes) by the use of the Smith and Hutton problem on the mass fraction transport equation. The importance of "false" or numerical diffusion is also addressed in connection with the simple description of a supply opening. The different aspects of boundary conditions in the indoor environment as, e.g., the simulation of Air Terminal Devices and the simulation of furnishings and occupants are discussed. The prediction of the flow in a room with a three-dimensional wall jet by the use of different turbulence models such as the k-epsilon model, the V2-f model and the Reynolds Stress model is addressed in the last chapter of the paper. PRACTICAL IMPLICATIONS The use of computational Fluid Dynamics as a practical design method for room air distribution is widespread. It is important to consider the quality of the predictions in order to obtain a sufficient level of accuracy. It is also important to work with a practical description of supply openings as well as with the right level of details in the occupied zone and the right turbulence model. All these aspects are addressed in the article.

UNLABELLED Air movement--good or bad? The question can only be answered by those who are exposed when they are exposed. Human perception of air movement depends on environmental factors including air velocity, air velocity fluctuations, air temperature, and personal factors such as overall thermal sensation and activity level. Even for the same individual, sensitivity to air movement may change from day to day as a result of, e.g., different levels of fatigue. Based on existing literature, the current paper summarizes factors influencing the human perception of air movement and attempts to specify in general terms when air movement is desirable and when it is not. At temperatures up to 22-23 degrees C, at sedentary activity and with occupants feeling neutral or cooler there is a risk of air movement being perceived as unacceptable, even at low velocities. In particular, a cool overall thermal sensation negatively influences the subjective perception of air movement. With occupants feeling warmer than neutral, at temperatures above 23 degrees C or at raised activity levels, humans generally do not feel draught at air velocities typical for indoor environments (up to around 0.4 m/s). In the higher temperature range, very high air velocities up to around 1.6 m/s have been found to be acceptable at air temperatures around 30 degrees C. However, at such high air velocities, the pressure on the skin and the general disturbance induced by the air movement may cause the air movement to be undesirable. PRACTICAL IMPLICATIONS Based on existing literature, the paper summarizes factors influencing the human perception of air movement and attempts to specify in general terms when air movement is desirable and when it is not.

UNLABELLED A study was performed in a call center that provides billing inquiry services using a 2 x 2 balanced experimental plan for nine consecutive weeks. Two independent variables, temperature and outdoor air supply rate, were combined and introduced to the occupants in a blind intervention approach. The temperature set-points were fixed at 22.5 degrees C and 24.5 degrees C, and outdoor air supply rate at 5 l /s/p and 10 l/s/p. Temperature and outdoor air supply rate had significant interaction effects on worker's talk time (P < 0.001), which means that the effects of temperature on talk time performance were not independent of the effects of outdoor air supply rate or the opposite. Talk time was reduced significantly when the outdoor air supply rate was increased from 5 l /s/p to 10 l/s/p at 24.5 degrees C (P < 0.01); this may be associated with the significant reduction in a principal component factor which includes intensity of dryness, aching eyes and nose-related symptoms (P < 0.01). Decreasing the temperature from 24.5 degrees C to 22.5 degrees C at 10 l /s/p significantly increased talk time (P < 0.01). Analysis of the principal component factor based on the neurobehavioral symptoms also revealed that temperature reduction led to an increased mean factor score of these symptoms (P < 0.04). PRACTICAL IMPLICATIONS For moderately complex office work which involves manipulation dexterity such as a call center operation where call operators interact with computer-based information systems, tropically acclimatized workers' performance could be improved by increasing the outdoor air supply rate from 5 l/s/p to 10 l/s/p if the temperature is to be maintained at the higher band of the thermal comfort range, around 24.5 degrees C. At a low ventilation rate (5 l/s/p), decreasing the temperature from 24.5 degrees C to 22.5 degrees C (which is a commonly adopted set-point in tropical office buildings) also leads to improvement of talk time performance. The magnitude of talk time improvement was greater by more than four times when the strategy to increase the outdoor air supply rate was implemented at a lower range of outdoor air supply rate (5-10 l /s/p) as compared to the higher range (9.8-22.7 l/s/p).

UNLABELLED Air movement can be characterized by its mean velocity, turbulent intensity, power spectra, velocity distribution probability, etc. Based on a field test, it was found that the characteristic of an artificial air movement is different from that of natural wind. In order to simulate the characteristic of natural wind, two air supply devices were investigated. Furthermore, the acceptability of the subjects exposed to the simulated natural wind is higher than that of subjects exposed to artificial air movement. Through the subjective assessment, the preferred mean air velocities at different ambient and supply air temperatures are presented. Finally, a conditioning mode using fluctuated air movement in warm climates, and a prediction of energy savings are given. PRACTICAL IMPLICATIONS The paper demonstrates how a simulated natural air movement may improve comfort and save energy in warm climates.

UNLABELLED Since the early twentieth century when air-conditioning began penetrating the market in a serious way, there has been a need for human factors research upon which HVAC engineering practice could be based. Now we have nearly a century of thermal comfort research from climate chambers and much has been learnt in that time. By stripping the research problem back to essential cause-and-effect variables, climate chamber methods have delivered results that are amenable to rigorous data analyses leading to unequivocal conclusions. However, in the minds of HVAC practitioners there are persistent doubts about the experiential realism of the chamber methodology, and the external validity of their findings, in particular, their relevance to building occupants going about their normal daily routines in fully-engineered indoor climatic environments. In response to this methodological concern in the 1990s, ASHRAE commissioned a series of thermal comfort studies aimed at field validating the findings of climate chamber research and the HVAC standards based upon them in a variety of climatic contexts around the world. This paper discusses the methodological benefits and constraints of conventional climate chamber research in comparison to the field-based alternative. In particular, issues such as sample size and demographics, research design, instrumentation and indoor climatic measurement procedures, questionnaires, clothing insulation and metabolic rate assessment techniques are analyzed. The discussion of methodology is then extended to the discipline of environmental psychology, which should have made a much more significant contribution to the topic of thermal comfort, and yet has remained relatively silent. The paper finishes by considering why engineers, most notably P.O. Fanger, have come to dominate a research topic that falls so clearly within the scope of psychology. HVAC engineering is the profession most directly occupied in the practice of thermal comfort, and therefore an engineer such as Fanger has been ideally qualified to design and conduct research, and even more important, presents its results in a way most directly useful to thermal comfort practitioners. PRACTICAL IMPLICATIONS The paper gives practical advice on evaluating and designing for thermal comfort.

Three human test series were conducted to evaluate the uniformity of the thermal environments in a stratum-ventilated chamber with dimensions of 8.8 m (L) × 5.1 m (W) × 2.4 m (H). In all, nineteen conditions were generated by adjusting the room temperature, supply airflow rate, and supply terminal type. An air diffuser performance index (ADPI) of at least 80% was achieved for most cases. This result shows that the air velocity and temperature in the occupied zone are reasonably uniform. Subjective assessments using the ASHRAE 7-point scale indicate that the thermal sensations of the subjects in stratum ventilation are also uniform. This study examines the applicability of the predicted mean vote (PMV) model for evaluating stratum ventilation. When compared to the actual mean thermal sensation votes (ATS), the PMV values are acceptable. The PMV results at a height of 1.1 m above the floor show better agreement with the ATS than at a height of 0.1 m.

To investigate whether occupants' anticipated control of their thermal environment can influence their thermal comfort and to explain why the acceptable temperature range in naturally ventilated environments is greater than that in air-conditioned environments, a series of experiments were conducted in a climate chamber in which the thermal environment remained the same but the psychological environment varied. The results of the experiments show that the ability to control the environment can improve occupants' thermal sensation and thermal comfort. Specifically, occupants' anticipated control decreased their thermal sensation vote (TSV) by 0.4-0.5 and improved their thermal comfort vote (TCV) by 0.3-0.4 in neutral-warm environment. This improvement was due exclusively to psychological factors. In addition, having to pay the cost of cooling had no significant influence on the occupants' thermal sensation and thermal comfort in this experiment. Thus, having the ability to control the thermal environment can improve occupants' comfort even if there is a monetary cost involved.

Thermal sensation has a large influence on thermal comfort, which is an important parameter for building performance. Understanding of thermal sensation may benefit from incorporating the physiology of thermal reception. The main issue is that humans do not sense temperature directly; the information is coded into neural discharge rates. This manuscript describes the development of a mathematical model of thermal sensation based on the neurophysiology of thermal reception. Experimental data from two independent studies were used to develop and validate the model. In both studies, skin and core temperature were measured. Thermal sensation votes were asked on the seven-point ASHRAE thermal sensation scale. For the development dataset, young adult males (N=12, 0.04Clo) were exposed to transient conditions; Tair 30-20-35-30°C. For validation, young adult males (N=8, 1.0Clo) were exposed to transient conditions; Tair: 17-25-17°C. The neurophysiological model significantly predicted thermal sensation for the development dataset (r2=0.89, P0.001). Only information from warm-sensitive skin and core thermoreceptors was required. Validation revealed that the model predicted thermal sensation within acceptable range (root mean squared residual=0.38). The neurophysiological model captured the dynamics of thermal sensation. Therefore, the neurophysiological model of thermal sensation can be of great value in the design of high-performance buildings.The presented method, based on neurophysiology, can be highly beneficial for predicting thermal sensation under complex environments with respect to transient environments.

Thermal sensation is studied experimentally under mixing ventilation, displacement ventilation, and stratum ventilation in an environmental chamber. Forty-eight subjects participated in all tests under the same boundary conditions but different ventilation methods in the classroom. Thermal comfort analysis was carried out according to the designated supply airflow rate, room temperature, and relative humidity for the three ventilation methods. The thermal neutral temperature under stratum ventilation is approximately 2.5 °C higher than that under mixing ventilation and 2.0 °C higher than that under displacement ventilation. This result indicates that stratum ventilation could provide satisfactory thermal comfort level to rooms of temperature up to 27 °C. The energy saving attributable to less ventilation load alone is around 12% compared with mixing ventilation and 9% compared with displacement ventilation.The confirmation of the significantly elevated thermal neutral temperature can have a number of implications for both thermal comfort in an air-conditioned room and energy consumption of the associate air-conditioning system. With respect to the former, it provides scientific basis for the feasibility of elevated room temperatures, and with respect to the latter, it reveals considerable potentials for energy saving.

Field measurements were collected through physical measurements and observations in the cities of Seoul, Korea; Eugene and Portland, Oregon; and Yokohama, Japan, during the fall, winter, and summer seasons from 2005 to 2006. A total of 1733 data sets were collected (Seoul - 713; Oregon - 807; Yokohama - 213) in variety of multi-use buildings with the goal of examining operative temperatures and conditions encountered during everyday life. Of the four cities measured, winter and autumn indoor operative temperatures were highest in Seoul and lowest in Yokohama when normalized to outdoor conditions. In contrast, summer indoor operative temperatures were highest in Yokohama and lowest in Oregon. Clothing levels changed seasonally, and differences were observed between 'long-term occupants', 'residents', and 'transients.'

This study investigated the thermal sensation of elderly people in Taiwan, older than 60 years, in indoor microclimate at home, and their requirements for establishing thermal comfort. The study was conducted using both a thermal sensation questionnaire and measurement of indoor climatic parameters underlying the thermal environment. Survey results were compared with those reported by Cheng and Hwang (2008, J. Tongji Univ., 38, 817-822) for non-elders to study the variation between different age groups in requirements of indoor thermal comfort. The results show that the predominant strategy of thermal adaptation for elders was window-opening in the summer and clothing adjustment in the winter. The temperature of thermal neutrality was 25.2 degrees C and 23.2 degrees C for the summer and the winter, respectively. Logistically regressed probit modeling on percentage of predicted dissatisfied (PPD) against mean thermal sensation vote revealed that the sensation votes corresponding to a PPD of 20% were +/- 0.75 for elders, about +/- 0.10 less than the levels projected by ISO 7730 model. The range of operative temperature for 80% thermal acceptability for elders in the summer was 23.2-27.1 degrees C, narrower than the range of 23.0-28.6 degrees C reported for non-elders. This is likely a result of a difference in the selection of adaptive strategies.Taiwan in the last decade has seen a rapid growth in the elderly population in its societal structure, and as such the quality of indoor thermal comfort increasingly concerns the elderly people. This study presents the results from field-surveying elders residing in major geographical areas of Taiwan, and discusses the requirements of these elders for indoor thermal comfort in different seasons. Through a comparison with the requirements by non-elders, this study demonstrates the unique sensitivity of elders toward indoor thermal quality and the selection of adaptive strategies that need to be considered when a thermal comfort zone is attempted in a household of members consisting of different age groups.

Results from naturally ventilated buildings show that allowing the indoor temperature to drift does not necessarily result in thermal discomfort and may allow for a reduction in energy use. However, for stationary conditions, several studies indicate that the thermal neutral temperature and optimum thermal condition differ between young adults and elderly. There is a lack of studies that describe the effect of aging on thermal comfort and productivity during a moderate temperature drift. In this study, the effect of a moderate temperature drift on physiological responses, thermal comfort, and productivity of eight young adults (age 22-25 year) and eight older subjects (age 67-73 year) was investigated. They were exposed to two different conditions: S1-a control condition; constant temperature of 21.5 degrees C; duration: 8 h; and S2-a transient condition; temperature range: 17-25 degrees C, duration: 8 h, temperature drift: first 4 h: +2 K/h, last 4 h: -2 K/h. The results indicate that thermal sensation of the elderly was, in general, 0.5 scale units lower in comparison with their younger counterparts. Furthermore, the elderly showed more distal vasoconstriction during both conditions. Nevertheless, TS of the elderly was related to air temperature only, while TS of the younger adults also was related to skin temperature. During the constant temperature session, the elderly preferred a higher temperature in comparison with the young adults.Because the stock of fossil fuels is limited, energy savings play an important role. Thermal comfort is one of the most important performance indicators to successfully apply measures to reduce the energy need in buildings. Allowing drifts in indoor temperature is one of the options to reduce the energy demand. This study contributes to the knowledge concerning the effects of a moderate temperature drift and the age of the inhabitants on their thermal comfort.

The benefits of thermal comfort and indoor air quality with personalized ventilation (PV) systems have been demonstrated in recent studies. One of the barriers for wide spread acceptance by architects and HVAC designers has been attributed to challenges and constraints faced in the integration of PV systems with the work station. A newly developed ceiling-mounted PV system addresses these challenges and provides a practical solution while retaining much of the apparent benefits of PV systems. Assessments of thermal environment, air movement, and air quality for ceiling-mounted PV system were performed with tropically acclimatized subjects in a Field Environmental Chamber. Thirty-two subjects performed normal office work and could choose to be exposed to four different PV airflow rates (4, 8, 12, and 16 L/s), thus offering themselves a reasonable degree of individual control. Ambient temperatures of 26 and 23.5 degrees C and PV air temperatures of 26, 23.5, and 21 degrees C were employed. The local and whole body thermal sensations were reduced when PV airflow rates were increased. Inhaled air temperature was perceived cooler and perceived air quality and air freshness improved when PV airflow rate was increased or temperature was reduced.The newly developed ceiling-mounted PV system offers a practical solution to the integration of PV air terminal devices (ATDs) in the vicinity of the workstation. By remotely locating the PV ATDs on the ceiling directly above the occupants and under their control, the conditioned outdoor air is now provided to the occupants through the downward momentum of the air. A secondary air-conditioning and air distribution system offers additional cooling in the room and maintains a higher ambient temperature, thus offering significant benefits in conserving energy. The results of this study provide designers and consultants with needed knowledge for design of PV systems.