Thermal Comfort Research Research Articles

A review of research on dynamic thermal comfort

Nowadays, people’s requirements for comfort are getting higher and higher, and traditional steady-state thermal comfort environment sometimes cannot meet people’s requirements. Dynamic thermal comfort is considered to meet people's requirements for comfort better than traditional thermal comfort, and it is also conducive to the health of occupants and building energy conservation. Therefore, this article reviews the literature on dynamic thermal comfort. First, this article briefly describes the transition from a steady-state thermal environment to a dynamic thermal environment. Next, this article reviews the research related to dynamic thermal comfort, such as the frequency of airflow fluctuations, simulation of natural wind, thermal prediction models, the use of intelligent detection equipment, and personal environmental control. This article summarizes the related research and development of dynamic thermal comfort from the aspects of dynamic airflow parameters, indoor thermal environment regulation, thermal experience, etc. This article aims to illustrate the necessity of the development of dynamic thermal comfort and its current results. The results show that under the trend of the artificial intelligence era, dynamic thermal comfort still has broad development potential. This article It can provide some research ideas for subsequent thermal comfort research. Practical application: This paper summarizes the research and development of dynamic thermal comfort from dynamic airflow, indoor thermal environment control, thermal experience, etc., and makes appropriate extensions and prospects accordingly. At the same time, the necessity of combining thermal comfort with AI trends is emphasized. This paper can provide references and ideas for thermal research on thermal comfort.

Dynamic thermal pleasure in outdoor environments - temporal alliesthesia

Thermal comfort research has been historically centred around the concept of “thermal neutrality”. Thermal neutrality originates from the steady-state indoor environment and is increasingly questioned when used to define the optimum sensation in outdoor environments. This calls for new criteria, designated for non-steady state and dynamically evolving outdoor settings. To address this need, we investigated thermal pleasure dynamics in outdoor environments based on thermal alliesthesia – a psychophysiological framework for understanding the hedonic responses elicited by non-steady-state thermal exposures. Detailed field studies were conducted in Sydney, Australia, during a 30-day period covering both summer and winter with a total of 35 subjects. The thermal sensation scale was quantitatively divided into four alliesthesial potential areas – two with moderate and two with strong alliesthesial potential - based on their divergence to the preferred sensation. We find that the temporal pleasure change (dP) can be predicted using thermal sensation change (dT). The results showed that linear regression performed strongly (R2 = 0.77 for summer and R2 = 0.79 for winter) in predicting dP when subjects' preceding sensation was in the strong alliesthesial potential zones – namely the ‘Hot’ and ‘Cold’ areas. When subjects' prior thermal sensation fell in the thermoneutral zone with moderate alliesthesial potential, a quadratic fit against dT provides a more reasonable prediction of dP (R2 = 0.61 for summer and R2 = 0.56 for winter). The dynamic thermal pleasure models provide a more nuanced subjective interpretation of outdoor urban spaces that includes thermal pleasure and delight. This study contributes further empirical support to the thermal alliesthesia framework and extends its application scope into outdoor thermal comfort research.

A thermodynamic model for official clothing insulation

Clothing insulation is an important factor in the thermal comfort research, and thus an accurate clothing insulation model is much required. This study develops a new model, which takes into account the sex difference for the dress. Its accuracy was verified experimentally, and the established thermodynamic model is useful to predict occupants? clothing behavior and to evaluate thermal comfort.

Performance of Aerated Concrete Blocks Under Varying Temperatures

Aerated concrete blocks (AC) are widely used as masonry in building construction because of their light weight and low density. Try to determine the strength, bonding, cracking and thermal behavior of aerated concrete blocks at different temperatures, mortar ratios and thickness. The results show that at temperatures above 100°C, the strength will decrease and cracks will appear, and the bonding behavior will vary with the thickness and proportion of the mortar. Compared with the solid concrete block model, Thermal Comfort Research shows better thermal comfort.

Building Thermal Comfort Research Based on Energy‐Saving Concept

Under the trend of building green and comfortable development, effective control of building energy consumption has become one of the problems that countries are actively facing to solve. People’s demand for residential buildings has changed from the past survival type to a comfortable and livable type. The high level of heating energy consumption is worthy of in‐depth study. In order to reduce energy consumption, realize the mapping of energy‐saving concepts in buildings, and understand the energy consumption of different building materials and the influence of external factors on human thermal comfort, this book has conducted research on building thermal comfort based on energy‐saving concepts. First of all, this article introduces the concept and application mode of energy‐saving concepts in buildings and the concept of thermal comfort and the SET index of standard effective temperature, including the two‐node model and the algorithm involved in the Fanger heat balance equation. In the experimental part, a model based on the concept of energy saving was designed to predict and analyze the energy consumption and thermal comfort effects of the building. In the analysis part, a comprehensive analysis of the effects of temperature, humidity, wind speed, and gender on thermal comfort, methods to improve thermal comfort, cumulative load changes with the heat transfer coefficient of windows, and the effects of windows of different materials on energy consumption was performed. At the same temperature, the wind speed is different, and the degree of heat sensation is also different. When the wind speed is 0.18 m/s and the temperature is 28°C, the thermal sensation is 0.32, and the human sensation is close to neutral. When the wind speed increases to 0.72 m/s, the heat sensation drops to −0.45, and the human body feels neutral and cool. It can be seen that the increase in wind speed has a certain compensation effect on the thermal sensation of the human body. When the wind speed does not change, increase the air temperature. For example, when the wind speed is 0.72 m/s, the temperature is 28°C, and the thermal sensation is −0.45, and when the temperature is increased to 29°C, the thermal sensation is 0.08, which shows that the temperature is improving the thermal sensation of the human body which has a certain offsetting effect. By studying the thermal comfort of buildings based on energy‐saving concepts, it is possible to obtain the effect of external factors on thermal comfort, thereby optimizing building materials and using building materials with lower heat transfer coefficients to reduce heating energy consumption.

From thermal sensation to thermal affect: A multi-dimensional semantic space to assess outdoor thermal comfort

The psychometric tool known as the thermal sensation scale has been extensively used in outdoor thermal comfort research. However, this one-dimensional descriptive scale was originally developed for indoor assessments and therefore has certain shortcomings in outdoor settings. The scale contains no affective information such as pleasure and it overlooks the dynamic wind and solar radiation fluxes outdoors. Accordingly, this study develops a six-dimensional semantic framework for outdoor thermal comfort assessments comprising four descriptive - ‘thermal sensation’, ‘humidity’, ‘wind’ and ‘solar radiation,’ plus two affective - ‘thermal pleasure’ and ‘thermal intensity’ dimensions. In Phase 1 an online questionnaire recruited 135 native English-speakers to place 76 climatic adjectives into this six-dimensional semantic space. Phase 2 launched a field study with another 22 subjects locating real-time outdoor thermal experiences in the same semantic space. They were then asked to select from a subset of the 76 climatic adjectives those that best described their right here-right-now thermal experience. Validation was then performed by comparing coordinates of the 31 most frequently chosen adjectives in Phase 2 with those assigned to them in Phase 1. Good correlations (R2 > 0.65) of adjectives' coordinates between the two research phases indicate consistency regarding which adjectives best describe specific scenarios, regardless of seasons, locations, or current exposures. The results emphasise that the thermal sensation scale inadequately characterises outdoor thermal comfort experiences. This study initiates the transition of biometeorological comfort research from crude unidimensional descriptive thermal sensation scale, towards a more nuanced, multi-dimensional descriptions of subjective thermal state.

Thermal comfort models and their developments: A review

• Reviewing thermal comfort models in different aspects. • Analyzing the advantages and disadvantages of all the models in the review. • Interpreting the importance of the models in different environments. • Suggesting some future developing directions of thermal comfort models. In the past several years, thermal comfort, especially development and application of thermal comfort model, has been a research focus of building environment. Since the 1970s, a series of thermal comfort models based on people's thermal sensation to environment have been established, and gradually became an important part of the field of thermal comfort research. In this review, the existing thermal comfort models are summarized from various perspectives, such as models applied in different environments like sleeping environment and outdoor environment. Besides, models used for different groups people, such as elderly and different races are discussed. In the part, adaptive models are mentioned. In additions, data-driven models were reviewed. This paper introduced the advantages and disadvantages of each model. Based on the above review, future research work of thermal comfort model is proposed.

The Visualization Study on Research Progress of Thermal Comfort for Indoor Environment Based on CiteSpace

The papers published from 2000 to 2019 in CNKI database were collected. CiteSpace software was used as visualization tool to analyze the research progress of indoor thermal comfort in China based on those papers. The results showed that the period, from 2000 to 2004, was the initial developing stage of researches on thermal comfort in China. From 2005 to 2019, there were two research fields developed of thermal comfort. One was to study the adaptive thermal comfort in different climates in China and try to promote the prediction model according to different climate characteristics. Another research keyword was to expand the field of thermal comfort research, e.g. studying the thermal comfort of the elderly and children, and studying rural houses and tall space buildings. Literature analysis also disclosed that “thermal sensation” and “thermal environment” were the core keywords in the field of thermal comfort from 2000 to 2019. According to research methods, “numerical simulation”, “field research” and “questionnaire” were commonly used. Recently, Thermal comfort under natural ventilation became the hot keyword in thermal comfort research. From 2011 to 2019, thermal comfort of rural housing had become a hot topic.

Development of a health data-driven model for a thermal comfort study

The objective of this study is to develop a thermal comfort model by incorporating public health datasets and influencing parameters associated with both health and thermal comfort. There are three systematic influencing parameters identified in this study: socioeconomic development, population density, and annual mean temperature. The thermal comfort neutral temperatures predicted with the new model are in good agreement with the measured field data, and the correlation coefficient is 0.91.The current study introduces large-scale spatial data and longitudinal health-temperature data from the public health field for contributing to thermal comfort research. For instance, the required numbers of intensive field experiments and modeling works regarding thermal comfort can be reduced. Moreover, studies on the impacts of certain factors (such as variations in time, gender, and age) on thermal comfort have not reached any conclusive results, mainly owing to a lack of large demographic datasets. Recent findings from the public health field indicate that there are observable variations in health-temperature data in response to climate changes. There are no significant health-temperature differences between genders, although females are more inclined to use resources for better environmental management. Other factors are also discussed in this study, such as age and the prevalence of air conditioners.

Rethinking indoor thermal comfort in the era of rebound and pre-bound effect for the developing world: A systematic review.

This paper presents a review on thermal comfort research that is informed by changes in occupant behavior, lifestyle, and income leading to rebound or pre-bound effect. It explores the current state of research in thermal comfort domain through a systematic review to identify the gaps and opportunities specifically focusing on energy-intensive developing countries. This review argues that adaptive thermal comfort is a continuously evolving domain owing to dynamic modifications in occupant behavior occurring from changes in the cost of energy services and preference of comfort (rebound/pre-bound effect). A conceptual framework linking thermal comfort, rebound/pre-bound effect, and occupant behavior is forwarded through the introduction of an exogenous factor related to occupant well-being. The results ascertain that there is a need of localized thermal comfort model with an occupant-centric approach that can help in enhancing comfort and reducing energy consumption.

Exploring thermal comfort experience and adaptive opportunities of female and male high school students

Students' health and productivity are affected by the thermal conditions inside the educational environments. Considering the lack of thermal comfort research in the Arabian Gulf region, the combination of the extreme climatic conditions, the general restriction on adaptive actions, and the lack of economic responsibility lead to heavy reliance on air conditioning units, which has environmental and economical sequences. A first step in reducing this reliance is understanding the students' thermal experiences. This paper attempts to feed the pool of thermal comfort research in the Arabic region by investigating and comparing the thermal conditions of female and male students considering their neutral temperatures and acceptability limits. Objective and subjective data were collected from five and three female and male schools respectively during the cooler season. Analysing the former data revealed the general similarity of the thermal conditions inside the investigated classrooms except for three classrooms. Around 50% of the female students were (neutral) compared with almost 20% of male students despite the heavier insulation level of the former, which may indicate an addiction to ACs for the male students. Applying Griffiths’ method, the neutral temperature was estimated at 24.3 ± 1.09 °C for the former students and 26.1 ± 0.92 °C for the latter students. Comparatively, the acceptability limits of the male students were shifted to the warm side of the thermal continuum.

The colours of comfort: From thermal sensation to person-centric thermal zones for adaptive building strategies

Thermal comfort research has been traditionally based on cross-sectional studies and spatial aggregation of individual surveys at building level. This research design is susceptible to compositional effects and may lead to error in identifying predictors to thermal comfort indices, in particular in relation to adaptive mechanisms. A relationship between comfort and different predictors can be true at an individual level but not evident at the building level. In addition, cross-sectional studies overlook temporal changes in individual thermal perception due to contextual factors. To address these limitations, this study applied a longitudinal research design over 8 to 21 months in eight buildings located in six countries around the world. The dataset comprises of 5,567 individual thermal comfort surveys from 258 participants. The analysis aggregated survey responses at participant level and clustered participants according to their thermal sensation votes (TSV). Four TSV clusters were introduced, representing four different thermal sensation traits. Further analysis reviewed the probability of cluster membership in relation to demographic characteristics and behavioural adaptation. Finally, the analysis at individual level enabled the introduction of a new metric, the thermal zone (Zt), which in this study ranges from 21.5 °C to 26.6 °C. The thermal sensation traits and person-centric thermal zone (Zt) are a first step into the development of new metrics incorporating individual perceived comfort into dynamic building controls for adaptive buildings.

Outdoor Thermal Comfort of Urban Park—A Case Study

Urban parks are an important component of urban public green space and a public place where a large number of urban residents choose to conduct outdoor activities. An important factor attracting people to visit and stay in urban parks is its outdoor thermal comfort, which is also an important criterion for evaluating the liability of the urban environment. In this study, through field meteorological monitoring and a questionnaire survey, outdoor thermal comfort of different types of landscape space in urban parks in Chengdu, China was studied in winter and summer. Result indicated that (1) different types of landscape spaces have different thermal comforts, (2) air temperature is the most important factor affecting outdoor thermal comfort; (3) because the thermal sensation judgment of outdoor thermal comfort research in Chengdu area, an ASHRAE seven-sites scale can be used; (4) the neutral temperature ranges of Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) in Chengdu in winter and summer were obtained through research; (5) and UTCI is the best index for evaluating outdoor thermal comfort in Chengdu. These findings provide theoretical benchmarks and technical references for urban planners and landscape designers to optimize outdoor thermal comfort in urban areas to establish a more comfortable and healthy living environment for urban residents.

The outdoor thermal comfort of urban square: A field study in a cold season in Chongqing

With the development of urban development and various outdoor activities, the outdoor activities time of residents continue to grow, and the good outdoor environment have an important impact on the physical and mental health of residents. For the winter outdoor thermal comfort problem with less attention, taking the Chongqing Three Gorges Square in the hot summer and cold winter area as an example, a winter thermal environment measurement and thermal comfort questionnaire were conducted. The Rayman software is used to calculate the PET (physiological equivalent temperature) value as thermal comfort evaluation parameters, establish a functional relationship between TCV (thermal comfort voting value), TSV (thermal sensation voting value) and PET. The winter thermal comfort range of different outdoor environmental spaces were obtained, and propose a suitable winter thermal comfort evaluation model for hot summer and cold winter area. The research results can provide basic data reference for the improvement of outdoor thermal comfort research in hot summer and cold winter areas.

Review of studies on thermal comfort in Indian residential buildings

This article presents a systematic review of thermal comfort studies in Indian residential buildings, to identify the present research scenario, data gaps, and policy interventions. The majority of the studies were performed in a composite climate (10), followed by a warm humid climate (seven), and a very few from cold (two) and hot and dry (two) climates. None of these thermal comfort studies took place in a temperate climate. In addition, seven studies have considered multiple climates for assessment of thermal comfort in residential buildings. This illustrates that thermal comfort studies in Indian residential buildings are scarce, scattered, and unorganized. Further, due to differences in sociocultural setup and local adaptations, wide variations in occupant comfort requirements were reported. This review argues that there are dynamic modifications in individual behaviors due to changes in cost of building energy services and comfort requirements. Only four of the reviewed studies partially considered the occupant behavior regarding control of the indoor thermal environment. The results obtained from these studies indicate that there is pressing need for the localized thermal comfort models that will improve not only the comfort requirements but also building energy performance. Importantly, this review paves the way for harmonised thermal comfort research in India, where a large amount of residential building stock is yet to be built.

Globe thermometer free convection error potentials

For thermal comfort research, globe thermometers have become the de facto tool for mean radiant temperature, tr, measurement. They provide a quick means to survey the radiant environment in a space with nearly a century of trials to reassure researchers. However, as more complexity is introduced to built environments, we must reassess the accuracy of globe measurements. In particular, corrections for globe readings taking wind into account rely on a forced convection heat transfer coefficient. In this study, we investigate potential errors introduced by buoyancy driven flow, or free convection, induced by radiant forcing of a black globe’s surface to a temperature different from the air. We discovered this error in an experimental radiant cooling system with high separation of air to radiant temperature. Empirical simulations and the data collected in a radiant cooling setup together demonstrate the influence of free convection on the instrument’s readings. Initial simulation and data show that tr measurements neglecting free convection when calculating tr from air temperatures of 2 K above tr could introduce a mechanism for globe readings to incorrectly track air temperatures. The experimental data constructed to test this hypothesis showed the standard correction readings are 1.94 ± 0.90 °C higher than the ground truth readings for all measurements taken in the experiment. The proposed mixed convection correction is 0.51 ± 1.07 °C higher than the ground truth, and is most accurate at low air speeds, within 0.25 ± 0.60 °C. This implies a potential systematic error in millions of measurements over the past 30 years of thermal comfort research. Future work will be carried out to experimentally validate this framework in a controlled climate chamber environment, examining the tradeoffs between accuracy and precision with globe thermometer measurements.

Bayesian updates for indoor thermal comfort models

Achieving thermal comfort through sustainable indoor design is an increasing concern. Thermal comfort modelling is crucial for achieving building energy saving. This study reviews and categorizes major developments and trends in the field of thermal comfort research in recent years. Discrepancies between actual and predicted results of thermal sensation and thermal satisfaction suggests a performance gap in Fanger's model. Based on the current research gaps identified, a practical solution is proposed to improve the reliability of thermal comfort predictions. Two Bayesian updating protocols, namely individual updating and global updating, are put forward and the use of Bayesian approach to systemically update current thermal comfort beliefs with openly available field data is demonstrated. Besides being a practical tool for modelling thermal comfort using the best information available (i.e. existing models and field survey data), the proposed Bayesian updating provides an achievable solution to the present challenges in establishing a reliable thermal comfort prediction model.

Defining the thermal sensitivity (Griffiths constant) of building occupants in the Korean residential context

Griffiths method is a widely used to estimate the comfort temperature of occupants. Although 0.5/K has been widely used as the representative thermal sensitivity (Griffiths constant) on various building types, this value was derived mainly from office data relying on assumptions that have not been fully field-validated (i.e., the assumption of no adaptive behavior occurring during the day). With an aim to empirically derive the thermal sensitivity (Griffiths constant) of occupants in residential settings, field monitoring was conducted in eleven households in South Korea. Within each household, physical indoor environmental data, subjective data and occupant behavioral data were recorded at 5 min intervals (from 8 a.m. to 8 p.m.). The value of the resulting regression coefficient (b) between the indoor temperature and the thermal sensation of occupants was estimated to be 0.356/K. This result indicates that the thermal sensation of the occupants of residential buildings is less sensitive to indoor temperature changes compared to that of occupants of other building types (e.g. offices 0.5/K). To increase the reliability of future thermal comfort research, the thermal sensitivity should reflect the characteristics of the building in question, rather than applying uncritically a generalized, universal Griffiths Constant such as 0.5/K.

Influence of Air Movement Preference on Thermal Comfort in Naturally Ventilated Classrooms of India

Background and objectives: Thermal comfort is very essential for a comfortable stay in any indoor space. Comfort conditions of indoor spaces are influenced by parameters like air movement, humidity, air temperature, etc. The aim of this research is to assess the air movement preferences by the occupants in classrooms of the selected higher education institutes in hot humid climate of India. Methods/statistical analysis: Surveys were conducted in all the three seasons of the year as per ASHRAE standard procedures. Environmental variables were measured in classrooms while questionnaires were distributed to the occupants simultaneously. A total of 361 students were surveyed with 1444 data sets for the whole year. Findings: Outdoor (Tout) temperatures were recorded and regression analysis has been done to find the relationship between the mean outdoor temperatures with the indoor operative temperatures (Top) recorded. The acceptance of air movement in classrooms during summer is 10–15.4%, in moderate season it is 5.6–30% and during winter it is up to 58%. Improvements/application: This study enables to understand the influence of air movement preference on occupant’s thermal comfort in classrooms of hot and humid climate of India. This will help in creating a comfortable environment in classrooms of higher education through placement and designing of openings for increased air movement thereby improving the thermal comfort conditions. This research assessed the movement of air in the classrooms of higher education and the occupants air movement preference for thermal comfort. This study is a starting point for the adaptive thermal comfort research in hot and humid climate of Vijayawada region. Keywords: Thermal Comfort, Air Movement Preference, Naturally Ventilated Classrooms, Environmental Factors

Experimental study on convective heat transfer coefficients for the human body exposed to turbulent wind conditions

Ongoing urbanization and urban densification are leading to an increasing number of tall buildings, giving rise to an increasingly complex urban morphology which, in turn, is complicating the pedestrian-level wind environment of urban areas. As a key climatic element determining pedestrian outdoor thermal comfort, wind is represented in most of the existing outdoor comfort models, but its effects have been oversimplified to date. This study aims to examine how wind velocity and turbulence intensity affect convective heat loss over a human body. A wind tunnel with a turbulence-grid is used to simulate outdoor wind flow with turbulence intensity ranging from 13% to 36%, and wind velocity from 0.7 m/s to 6.7 m/s. Forced convective heat loss for individual body segments have been measured on a thermal manikin using a constant skin temperature regulation mode. Results for unit effect confirm that convective heat loss increases with turbulence intensity, which prompts us to make explicit the turbulence intensity when calculating the heat loss from human body. Ignoring turbulence causes the impact of wind on pedestrian thermal sensation to be underestimated by up to 50%. Based on the present data, regression formula derived from regular geometry for predicting convective heat transfer coefficients has been expanded to serve individual body segments. Accounting for the effect of both wind velocity and turbulence intensity, the accuracy of convective heat loss calculations in outdoor thermal comfort research would be improved.