Using the adaptive model of thermal comfort for obtaining indoor neutral temperature: Findings from a field study in Hyderabad,India

There is a dearth of thermal comfort studies in India. It is aimed to investigate into the aspects of thermal comfort in Hyderabad and to identify the neutral temperature in residential environments. This was achieved through a thermal comfort field study in naturally ventilated apartment buildings conducted during summer and monsoon involving over 100 subjects. A total of 3962 datasets were collected covering their thermal responses and the measurement of the thermal environment. The comfort band (voting within –1 and +1), based on the field study, was found to be 26–32.45°C, with the neutral temperature at 29.23°C. This is way above the indoor temperature standards specified in Indian Codes. It was found that the regression neutral temperature and the globe temperature recorded when voting neutral converged when mean thermal sensation of the subjects was close to 0. This happened during the period of moderate temperature when the adaptive measures were adequate. The indoor temperatures recorded in roof-exposed (top floor) flats were higher than the lower floors. The thermal sensation and preference votes of subjects living in top floors were always higher. Consequently, their acceptance vote was also lower. It was found that the subjects living in top floor flats had a higher neutral temperature when the available adaptive opportunities were sufficient. This was due to their continuous exposure to a higher thermal regime due to much higher solar exposure. This study calls for special adaptive measures for roof-exposed flats to achieve neutrality at higher temperature.     

An analysis of bioclimatic zones and implications for design of outdoor built environments in Egypt

Climate considerations are essential dimensions in the assessment of quality of outdoor built environments. This paper provides an analysis of bioclimatic classification of Egypt to help the environmental design of wide range of purposes, including: climate responsive design; energy conservation and thermal comfort in the outdoor built environments. The analysis of this classification uses a bioclimatic approach in which the comfort zone and monthly climatic lines were determined and plotted on the psychrometric chart. Since the mean radiant temperature (T_mrt) is the most important input parameter for the energy balance in outdoor environments, the charts apply the ASHRAE 55-2004 standard considering the operative temperature as a function of T_mrt. Analysis for each bioclimatic zone determines the potential of passive design strategies to maintain thermal comfort in outdoor spaces and to contribute to energy efficient built environment. Finally, this study suggests a design guideline matrix for landscape architectural design for the different bioclimatic zones.     

Research on seasonal indoor thermal environment and residents' control behavior of cooling and heating systems in Korea

Indoor thermal environments and residents' control behavior of cooling and heating systems were investigated in Seoul, Korea and compared with the results of previous studies. Twenty-four houses in summer, six houses in autumn and 36 houses in winter were used in this study. The measurement of temperature, humidity and air conditioner usage behavior was carried out. The clo-value, thermal comfort, sensation and basic data of the houses were also investigated. The indoor thermal environment in the summer had a high temperature and a high humidity ratio compare to standard comfort zone. Most of the indoor thermal environments at the time of starting the air conditioner in the summer were out of the comfort zone. Some of the data recorded while the air conditioner was stopped were in the comfort zone, but in many cases the temperature was relatively higher than comfort zone. Most indoor climate distributions in the winter were in the comfort zone and the indoor climate in autumn coincided well with the criteria of the comfort zone. Compared with results of previous studies in these 25 years, indoor ambient average temperature in winter has increased and the comfort temperature has increased in the heating period and decreased in the cooling period. This result indicates that the development of an HVAC system has created an expectation of comfort for residents and has shifted their thermal comfort zone warmer in winter and cooler in summer.     

Survey of thermal comfort in residential buildings under natural conditions in hot humid and cold wet seasons in Nanjing

Comfort standards (ISO 7730, ASHRAE 55) specify the exact physical criteria for producing acceptable thermal environments, such as temperature, air movement, and humidity limits. These, however, are often difficult to comply with, particularly in hot humid and cold wet seasons in Nanjing, China. Changing expectations of comfort is important in evaluating comfort, since naturally conditioned buildings in Nanjing are not typically air-conditioned. For this objective, a field study was conducted during the summer of 2000 and the winter of 2001. A total of 600 participants each answered a subjective questionnaire. Analyzing these field data shows that in natural conditions, the influence of gender and age on people’s thermal sensations is insignificant compared with six main variables. In addition, people’s thermal discomfort rapidly increases along with growth in relative humidity. Further, the variation of people’s hot or cold sensations is in proportion to that of air movement, and the effect in winter is greater than that in summer. The range of acceptable temperatures in hot humid and cold wet Nanjing is between 14.14°C and 29.42°C.     

Evolving opportunities for providing thermal comfort

The building industry needs a fundamental paradigm shift in its notion of comfort, to find low-energy ways of creating more thermally dynamic and non-uniform environments that bring inhabitants pleasure. Strategies for providing enriched thermal environments must be conjoined with reducing energy; these are inseparable for any building striving for high performance. The objective of current comfort standards is to have no more than 20% of occupants dissatisfied, yet buildings are not reaching even that scant goal. A significant energy cost is incurred by the current practice of controlling buildings within a narrow range of temperatures (often over-cooling in the summer). If building designers and operators can find efficient ways to allow building temperatures to float over a wider range, while affording occupants individual control of comfort, the potential for energy savings is enormous. Five new ways of thinking, or paradigm shifts, are presented for designing or operating buildings to provide enhanced thermal experiences. They are supported by examples of research conducted by the Center for the Built Environment, and include shifts from centralized to personal control, from still to breezy air movement, from thermal neutrality to delight, from active to passive design, and from system disengagement to improved feedback loops.     

Web application for thermal comfort visualization and calculation according to ASHRAE Standard 55

Thermal comfort is one of the fundamental aspects of indoor environmental quality and it is strongly related to occupant satisfaction and energy use in buildings. This paper describes a new web application for thermal comfort visualization and calculation according to ASHRAE Standard 55-2013. Compared to existing software, the web application is free, cross-platform, and provides a visual and highly interactive accurate representation of the comfort zone. Its main features are: dynamic visualization of the comfort zone on psychrometric, temperature-relative humidity, and adaptive charts; new implementation of the Elevated Air Speed model; local thermal discomfort assessment; compliance document automation for LEED thermal comfort credits; metabolic activity and clothing insulation tables and dynamic models; and compliance with the standard. The tool can be used by architects, engineers, building operators, educators, and students.     

Thermal pleasure in built environments: physiology of alliesthesia

International standards that define thermal comfort in uniform environments are based on the steady-state heat balance equation that posits ‘neutrality’ as the optimal occupant comfort state for which environments are designed. But thermal perception is more than an outcome of a deterministic, steady-state heat balance. Thermal alliesthesia is a conceptual framework to understand the hedonics of a much larger spectrum of thermal environments than the more thoroughly researched concept of thermal neutrality. At its simplest, thermal alliesthesia states that the hedonic qualities of the thermal environment are determined as much by the general thermal state of the subject as by the environment itself. A peripheral thermal stimulus that offsets or counters a thermoregulatory load-error will be pleasantly perceived and vice versa, a stimulus that exacerbates thermoregulatory load-error will feel unpleasant. The present paper elaborates the thermophysiological hypothesis of alliesthesia with a particular focus on set-point control and the origins of thermoregulatory load-error signals, and then discusses them within the broader context of thermal pleasure. Alliesthesia provides an overarching framework within which diverse and previously disconnected findings of laboratory experiments, field studies and even comfort standards spanning the last 40 years of thermal comfort research can be more coherently understood.     

Comfort,perceived air quality,and work performance in a low-power task–ambient conditioning system

Zhang's thermal comfort model [Zhang H. Human thermal sensation and comfort in transient and non-uniform thermal environments, Ph.D. thesis, UC Berkeley; 2003. 415 pp.] predicts that the local comfort of feet, hands, and face predominates in determining a person's overall comfort in warm and cool conditions. We took advantage of this in designing a task–ambient conditioning (TAC) system that heats only the feet and hands, and cools only the hands and face, to provide comfort in a wide range of ambient environments. Per workstation, the TAC system uses less than 41 W for cooling and 59 W for heating. We tested the TAC system on 18 subjects in our environmental chamber, at temperatures representing a wide range of practical winter and summer conditions (18–30 °C). A total of 90 tests were done. We measured subjects' skin and core temperatures, obtained their subjective responses about thermal comfort, perceived air quality, and air movement preference. The subjects performed three different types of tasks to evaluate their productivity during the testing. The TAC system maintains good comfort levels across the entire temperature range tested. TAC did not significantly affect the task performance of the occupants compared to a neutral ambient condition. Whenever air motion was provided, perceived air quality was significantly improved, even if the air movement was re-circulated room air. In our tests, subjects found thermal environments acceptable even if they were judged slightly uncomfortable (−0.5). By reducing the amount of control normally needed in the overall building, the TAC system saves energy. Simulated annual heating and cooling energy savings with the TAC system are as much as 40%.     

Experimental study of the influence of anticipated control on human thermal sensation and thermal comfort

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.     

Field study on occupants’ thermal comfort and residential thermal environment in a hot-humid climate of China

This paper discusses thermal comfort inside residences of three cities in the hot-humid climate of central southern China. Only a few thermal comfort studies have been performed in hot-humid climates and none in Central Southern China. Field sampling took place in the summers of 2003 and 2004 by obtaining 110 responses to a survey questionnaire and measuring environmental comfort variables in three rooms in each of 26 residences. The objectives are to measure and characterize occupant thermal perceptions in residences, compare observed and predicted percent of dissatisfied and discern differences between this study and similar studies performed in different climate zones. Average clothing insulation for seated subjects was 0.54 clo with 0.15 clo of chairs. Only 48.2% of the measured variables are within the ASHRAE Standard 55-1992 summer comfort zone, but approximately 87.3% of the occupants perceived their thermal conditions acceptable, for subjects adapt to prevailing conditions. The operative temperature denoting the thermal environment accepted by 90% of occupants is 22.0–25.9°. In the ASHRAE seven-point sensation scale, thermal neutral temperature occurs at 28.6°. Preferred temperature, mean temperature requested by respondents, is 22.8°. Results of this study can be used to design low energy consumption systems for occupant thermal comfort in central southern China.     

Thermal pleasure in built environments: spatial alliesthesia from contact heating

The comfort zone is bounded by thermal environmental conditions that may be described as acceptably cool or acceptably warm, and engineering out of existence these innocuous thermal conditions on the fringes of the adaptive comfort range may not be necessary. In contrast to the conventional understanding of local discomfort, spatial alliesthesia exploits corrective differences in the rate of change in skin temperature between individual body segments to elicit positive affective sensations. This paper examines reverse instances of local discomfort, or spatial alliesthesia, from warm contact stimuli applied to hand and feet when exposed to ambient conditions towards the lower margin of the comfort zone. It was found that subjects with moderate feelings of displeasure or even indifference were still capable of experiencing a pleasant response to localized thermal stimuli. Brief whole-body thermal pleasure was observed from in-situ skin temperature changes at a single distal body site. These effects were subtle and not universally experienced, so the success of their deliberate implementation in built environments depends heavily on some form of individual control. Spatial alliesthesia therefore complements the body of literature investigating personal environmental control and local thermal discomfort by providing a theoretical framework of thermal perception in non-neutral environments.     

Natural ventilation potential for gymnasia-Case study of ventilation and comfort in a multisport facility in northeastern United States

The natural ventilation potential to maintain acceptable indoor air quality(IAQ) and thermal comfort in gymnasia was investigated using a university multisport facility in northeastern United States as a case study building. A parametric modeling study was conducted considering the effects of opening configurations and control strategies during the summer months. The thermal accuracy of the model was verified using field measurements during August 2015. Performance metrics for IAQ and thermal comfort were the percentages of occupied hours during which ventilation rate met or exceeded ASHRAE Standard 62.1-2013 and temperature met adaptive thermal comfort criteria of ASHRAE Standard55-2013, respectively. Wind direction was found having a major effect on cross ventilation rate. Wind and buoyancy driven forces could complement or oppose each other depending on the wind direction and opening position. Relative to the base case, larger net openings that were more evenly distributed performed better.Rooftop vents improved ventilation performance, particularly under unfavorable wind conditions. With improved opening configurations, the acceptable ventilation hours increased from 21.5% to99.5% of occupied time for the maximum occupancy. The strictest temperature-controlled strategy had the best thermal performance.Thermal comfort conditions could be maintained during 85.3% of the occupied hours. However, the temperature rule largely shortened the opening operation time, and consequently decreased the acceptable ventilation hours to only 47.1%. Continuously natural ventilation during occupied time gave the longest combined IAQ-thermal acceptable hours, 73.9% of the occupied time, although it moderately decreased the thermal comfort hours to74.2%.     

Extended predicted mean vote of thermal adaptations reinforced around thermal neutrality

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.     

Gender differences in thermal comfort and use of thermostats in everyday thermal environments

Differences in thermal comfort between male and female subjects are generally considered to be small. In this study gender differences in thermal comfort and use of thermostats were examined by a quantitative interview survey with a total of 3094 respondents, and by controlled experiments. The studies were carried out in Finland and considered everyday thermal environments: homes, offices and a university. The results show significant gender differences in thermal comfort, temperature preference, and use of thermostats. Females are less satisfied with room temperatures than males, prefer higher room temperatures than males, and feel both uncomfortably cold and uncomfortably hot more often than males. Although females are more critical of their thermal environments, males use thermostats in households more often than females.     

Field experiments on thermal comfort in campus classrooms in Taiwan

This paper presents the results of the ASHRAE methodology for thermal comfort study applied in Taiwan. Field experiments conducted in 10 naturally ventilated and 26 air-conditioned campus classrooms used survey questionnaires and physical measurements to collect data. A total of 944 individuals in seven universities completed 1294 questionnaires. The chi-square tests were applied to find the significant aspects that affect students’ thermal sensations. The results show that air temperature, air movement and mean radiant temperature have significant influence, but humidity has no statistical significance. By using probit regressive analyses, the thermal neutrality and thermal preference of students occurred at 26.3 °C ET^* and 24.7 °C ET^*, respectively. Responses from those students suggest a wider acceptable temperature range for occupants in Taiwan. The margins of the acceptable zones obtained from direct and indirect acceptability assessing methods are 21.1–29.8 °C ET^* and 24.2–29.3 °C ET^*, respectively. When compared with similar studies elsewhere, this finding supports the sentiments on climatic adaptation.     

Adaptive thermal comfort and sustainable thermal standards for buildings

The origin and development of the adaptive approach to thermal comfort is explained. A number of recent developments in the application of the theory are considered and the origin of the differences between adaptive thermal comfort and the ‘rational’ indices is explored. The application of the adaptive approach to thermal comfort standards is considered and recommendations made as to the best comfort temperature, the range of comfortable environments and the maximum rate of change of indoor temperature. The application of criteria of sustainability to thermal standards for buildings is also considered.     

Effect of age, gender, economic group and tenure on thermal comfort: A field study in residential buildings in hot and dry climate with seasonal variations

Energy consumption in Indian residential buildings is one of the highest and is increasing phenomenally. Indian standards specify comfort temperatures between 23 and 26 °C for all types of buildings across the nation. However, thermal comfort research in India is very limited. A field study in naturally ventilated apartments was done in 2008, during the summer and monsoon seasons in Hyderabad in composite climate. This survey involved over 100 subjects, giving 3962 datasets. They were analysed under different groups: age, gender, economic group and tenure. Age, gender and tenure correlated weakly with thermal comfort. However, thermal acceptance of women, older subjects and owner-subjects was higher. Economic level of the subjects showed significant effect on the thermal sensation, preference, acceptance and neutrality. The comfort band for lowest economic group was found to be 27.3-33.1 °C with the neutral temperature at 30.2 °C. This is way above the standard. This finding has far reaching energy implications on building and HVAC systems design and practice. Occupants’ responses for other environmental parameters often depended on their thermal sensation, often resulting in a near normal distribution. The subjects displayed acoustic and olfactory obliviousness due to habituation, resulting in higher satisfaction and acceptance.     

In search of the comfortable indoor environment: A comparison of the utility of objective and subjective indicators of indoor comfort

Today, many procedures for assessing the indoor environment rely on both subjective and objective indicators (e.g. ANSI/ASHRAE 55-2004; ISO 10551). It is however unclear how these two types of measurements are related to perceived comfort. This article aims at assessing the relative utility of subjective (rating scale measures) and objective indicators of perceived comfort of indoor environments. In a hospital setting, physical environmental variables (e.g. temperature, relative humidity and noise level) were simultaneously measured as respondents (both patients and staff) rated their perception of the indoor environment. Regression analyses indicated that the subjective sensory ratings were significantly better than objective indicators at predicting overall rated indoor comfort. These results are discussed in relation to existing measurement procedures and standards.     

湿热地区老年人夏季室外热舒适阈值研究

旨在探索湿热地区老年人夏季室外热舒适阈值。以课题示范工程、样本量集中的广州市老人院为研究案例,结合现场实测与问卷调研,获得各气象要素（空气温度、相对湿度、黑球温度、风速）的逐时数据及老年人室外热舒适状况;借助Rayman模型,计算生理等效温度PET,运用SPSS进行回归分析建立老年人室外热舒适评价模型;并评析不同类型测点空间的热环境情况与特点。结论如下：（1）湿热地区夏季老年人室外热环境中性PET值为25.60℃;台湾、香港、广州等湿热气候地区,老年人与混合年龄层中性PET值接近,人群中性PET值具有一定普适性;（2）老年人热感觉中性范围为23.79℃~27.41℃,较混合年龄层窄;老年人室外环境热舒适PET范围为22.70℃~32.53℃,老年人对偏凉感觉（PET=23.10℃）更感舒适;老年人达到90%可接受率的PET范围是22.62℃~31.15℃;（3）老年人夏季热敏感度为3.62PET（℃）/TSV,夏季老年人对室外热环境敏感度明显高于混合年龄层,因此室外热环境设计对老年人具有更大影响;（4）在适当遮荫条件（植物或建筑）下,老年人在夏季依然乐于接受室外阳光辐射;但需综合运用遮阳、通风、降温等设计策略才能满足老年人对热环境的舒适需求。以期为湿热地区室外环境适老设计提供研究方法和设计目标的参考。     

Predicted and reported thermal sensation in climate chambers,offices and homes

Past thermal comfort research has shown differences in the thermal sensation votes given in field and laboratory settings. However, such research tends to compare the votes of different groups of people in different environments rather than comparing the same people in each environment. Therefore, a two-phase study was conducted of the thermal comfort of 30 BRE employees in their home, in their office, and in a climate chamber. In the first phase each subject spent two 3 h sessions in each environment and the temperature was adjusted between sessions within the range 18–26°C. Data loggers were used to record the air and mean radiant temperature, air velocity and relative humidity; subjective ratings of thermal sensation were obtained using questionnaires. The subjects wore the same clothing in each session and were allowed to conduct only sedentary activities. The reported thermal sensation votes were compared with those predicted using ISO 7730. The observed neutral temperatures for each of the three environments differed by up to 2°C and were up to 1°C different to those predicted. This finding has implications for energy use. In the second phase, the subjects were studied in their home and office only. No restrictions were imposed on clothing, previous or current activities, or environmental conditions. The observed thermal sensation votes were very poorly correlated with those predicted and with operative temperature.