Thermal Comfort Studies Research Articles

User response to indoor thermal environment in female high school buildings in Oman

ABSTRACT Thermal comfort has a regional nature as it is affected by people’s climatic and cultural background. Under the extreme climate of Oman, the absence of local standards combined with the lack of thermal comfort studies in educational buildings, and the relatively long-time students spend daily in classrooms, highlights the importance of conducting such studies. In this research, the indoor and outdoor measurements of air temperature (Ta), globe temperature (Tg), relative humidity (RH), and air velocity (AV) were combined with the findings of four questionnaires distributed among female school students to explore their responses to the classrooms' thermal environments. The findings indicated that around 66–83% of the students expressed satisfaction with the thermal conditions in their classrooms with around 61–79% feeling comfortable. The neutral temperature was computed as 24.9 ± 2.48°C applying Griffiths’ method and a slope of 0.5/K. The acceptability limits for satisfaction levels of 80% and 90% were 23.3–26.6°C and 23.9–25.9°C, respectively. The research findings provide information that may be used to manage how the classrooms are managed in relation to the use of air conditioning and window opening, as well as valuable information about how the students adjust their clothing to maintain thermal comfort.

Thermal Comfort Study Based on PMV-PPD in the Building of a Screening Center for COVID-19

Background: One way to achieve a standard heating, ventilating, and air conditioning system with maximum satisfaction is to use a thermal index to identify and determine the thermal comfort of people. In this study we intend to evaluate thermal comfort based on PMV-PPD (Predicted Mean Vote/Predicted Percentage Dissatisfied) model in workers of screening center for COVID-19. Methods: The study period was from March 1 to October 31, 2020. In this study, we used the ISO 7730 model to determinate PMV-PPD index. PMV index was used to determine thermal comfort at different scales in Birjand city with arid and hot climate. All data were analyzed using R software (version 3.3.0) and IBM SPSS statistics softwares. Results: The maximum and minimum recorded physical PMV values in the study period were observed in June as (2.09 ± 0.03) and March as (-1.27 ± 0.14), respectively. The amplitude of the thermal sense in the study period was varied between slightly cool (-1.5) and warm (+2.5). The PPD in spring was 40% which indicated slightly warm to hot condition. Conclusions: The October was the only month during the study in which thermal stress was in comfort or neutral thermal condition. Our results suggest that thermal comfort has dimensions and indices which are helpful in managing energy consumption.

EMERGING NEED FOR MICRO-CLIMATIC CONSIDERATIONS IN URBAN DESIGN PROCESS: A REVIEW

The effects and consequences of climate change have been extensively considered in the urban design qualities. The climatic factors directly affect human activities in urban spaces, particularly in the pedestrian environment. The global issues on climate change could be well understood by understanding the contributions of climatic conditions towards thermal environmental discomforts. So, the roles and processes in urban design can be enhanced to reduce the impacts of extreme urban climate on pedestrian experiences. This current article focused on the systematic review of thermal comfort through urban designing, detailing the objectives, methods used, and the body of knowledge to deal with this issue. This paper also summarizes the current understanding and challenges in addressing the microclimatic analysis roles in human life by discussing the thermal comfort studies and literature regarding human, building, and city levels. Finally, this systemic study demonstrated the needs and potential assessments based on the quality and standardization of human-centric data collection and interpretation. It specifically addressed an urban planner's structure that could be used as an empirical method during the urban planning processes. In conclusion, the applications of the recommended methods identified in this study aid in the design decisions to shift towards climate comfort in urban spaces.

Comfortable and partial warm environment increases salivary S-IgE concentration in healthy adults

An indoor thermal environment stimulates the human endocrine system, thermoregulation system, and nervous system, which significantly affects immunity. However, the effect of environmental temperature on immunity was not included in the field study of thermal comfort. To achieve this, we considered three different temperatures (18, 24, and 30 °C). Skin surface temperature, unstimulated whole saliva, thermal sensation vote, and thermal comfort vote from ten subjects under each condition were acquired simultaneously. The same subjects and experiment were repeated once in different years. Salivary secretory immunoglobulin E (S-IgE) concentration was measured using an enzyme-linked immunosorbent assay. Our results indicate that environmental temperature significantly affected salivary S-IgE concentration (P = 0.015), When the environmental temperature increased from 18 to 24 to 30 ℃, the IgE concentration in saliva gradually increased. The S-IgE concentration was the highest when the thermal sensation and thermal comfort were close to neutral and comfortable, which was 143.7% higher than the very uncomfortable. The S-IgE concentration was significantly positively correlated for thigh, back, forehead temperature, and average skin temperature (P = 0.023, P = 0.045, P = 0.021, P = 0.018, respectively). A comfortable and warm environment may enhance oral mucosal immunity by increasing the concentration of S-IgE in the saliva.

Studies of ventilation and thermal comfort in different wind tower-room configurations considering humidification for a warm climate of Mexico

Air conditioning systems in buildings demand a high energy consumption and will only be exacerbated by the threat of climate change, as coping with the increased temperatures will require a higher consumption of electricity for ventilation and cooling. The use of passive techniques to save energy and provide thermal comfort inside the buildings should be a priority for research. This work investigates the effectiveness of the passive natural ventilation system called the wind tower (windcatcher) to provide thermal comfort in a room without and with air humidification, for warm climatic conditions. The study was carried out using CFD considering three-dimensional turbulent flow for the continuous phase and a Lagrangian approach for the discrete phase. In addition, the parameters and indices of natural ventilation and thermal comfort were calculated. 54 different configurations of the wind tower and the room outlet window were evaluated. The influence of a chamfer in the tower and the optimization of water consumption in the humidifier were also investigated. The results showed that the selection of a suitable configuration and the use of a chamfer, can substantially improve ventilation and thermal comfort. In addition, the optimal mass flow rate for humidification that provides a sensation of neutral thermal comfort and minimal water consumption was found. The use of a wind tower and the application of humidification at the critical hours of the day, will provide thermal comfort throughout the day with a predicted percentage of dissatisfied lower than 10%. These results show that low energy consuming systems utilizing natural ventilation and air humidification in a wind tower-room system can be sufficient for appropriate cooling and thermal comfort.

A simple technique for the traditional method to estimate mean radiant temperature.

The mean radiant temperature (Tmrt) is the most important meteorological factor influencing human thermal comfort in urban areas. Numerous methods have been implemented for estimating Tmrt using measured radiometer or thermometer data, and exhibit different levels of accuracy. This study presents a simple technique based on the traditional method (Tmrt_TM) to estimate Tmrt by utilizing measured radiation data from the radiometers. The estimated Tmrt values from the six-directional method (Tmrt_SM) and two black globe thermometer methods (Tmrt_BG and Tmrt_BGv) at two stations (sky view factor 0.69 and 0.94) in Jeju, Republic of Korea, for 8days (5 sunny days, 3 (semi-) cloudy days) in spring and summer were used to validate the Tmrt_TM. The results showed that the mean differences between Tmrt_TM and Tmrt_SM were within the required accuracy for comfort in ISO 7726 (± 2 ℃) on sunny days and were reduced to 0.1-0.3 ℃ in high Tmrt conditions such as clear summer days. The Tmrt_BG in most sunny and semi-cloudy days and Tmrt_BGv on all days resulted in large mean differences from the Tmrt_TM that exceeded the required accuracy for thermal stress in ISO 7726 (± 5 ℃). Therefore, both black globe thermometer methods should be used carefully when estimating Tmrt, especially during sunny days. The correlations between Tmrt_TM and Tmrt_SM were highly significant, 0.93 on all days (p = 0.01). The newly developed regression equations between Tmrt_TM and Tmrt_SM could reduce mean differences within 0.5 ℃ for all days, and their r2 values exceeded 0.87. Therefore, the simple Tmrt_TM technique can be used for Tmrt estimation in human thermal comfort studies.

Case Study of Thermal Comfort in a Temporary Shelter

In Latvia to perform COVID-19 tests as well as for temporary shelters in case of a local disease outbreak the persons were located in special tents. Such practice was not only performed locally but also in other countries like the USA, UK, Russia, etc. The wide usage of tents was possible as the outbreak happened during the warm period of the year. At the same time, the indoor climate of tents can be quite unbearable during the warm summer days. Also, the situation was not getting better as fast as the prognosis, and the crisis was still ongoing during the winter period. Therefore, to test the thermal comfort of such temporary shelter’s measurements were performed. The thermal comfort was measured in a tent from 27th May to 28th September 2020. The data was logged with three different measuring devices inside of the shelter as well as outside air parameters like temperature and solar radiation was logged. The results show the rapidly changing indoor temperature which reaches 40°C during the daytime and falls to 10°C at night. The data of the globe thermometer to analyze the influence of radiation from tent canvas was also studied and showed that there is no noticeable heat radiation from external walls. The PMV measurements showed that the thermal comfort is very low as the PMV values were outside the range of -1 to 1 for 57% of the time. The influence of the precipitation was also noted, and the results showed that the adiabatic cooling effect is very variable but in general does not noticeably change the indoor temperature, the average temperature decrease was only 1 °C, but for a specific case it reached 10°C.

Outdoor performance of the black globe temperature sensor on a hot and humid tropical region

ABSTRACT A crucial variable to evaluate thermal comfort is the mean radiant temperature (Tmrt). In this paper we evaluate the performance of the 150 mm black globe thermometer to provide reliable Tmrt values for outdoor settings in Singapore. Accurate Tmrt values are calculated by the method of integral radiation measurements. Based on these, the mean convection coefficient of the black globe has been re-calibrated. Results show an improvement in the estimation of Tmrt with the new coefficient in comparison with the default version suggested in ISO7726:1998. Increasing the averaging periods of the measured variables improved the performance of the derived mean convective coefficients to estimate Tmrt. During clear skies day and for 10-min averaged data, RMSE for Tmrt reduce to 3.9 °C (7.4 °C for ISO7726:1998 coefficient) with an overestimation on high incoming solar radiation periods and an underestimation during the morning and evening (low solar elevation). During overcast dry conditions an underestimation of Tmrt is also expected which is higher in the rain/wet periods. The mean convective coefficient presented in this work can provide improved estimations of Tmrt relevant for outdoor thermal comfort studies in hot and humid tropical climates like Singapore.

Experimental study of thermal comfort in a field environment chamber with stratum ventilation system in winter

Stratum ventilation has potentials to be used for winter heating. Both local and overall thermal perceptions are essential for ensuring indoor satisfactory thermal environments. This study aimed to comprehensively investigate the subjective perceptions in a field environment chamber heated by stratum ventilation. The chamber was configured as a two-row classroom. Eleven cases were conducted with supply air velocities of 0.8–1.4 m/s and supply air temperatures of 23–30 °C. With room air temperatures of approximately 20–24 °C, thirty-six subjects were recruited to evaluate the thermal environments. The questionnaires concerned overall thermal sensation and comfort (OTS and OTC), local thermal sensation and comfort (LTS and LTC), draft sensation, and humidity sensation. The results showed that the OTS conformed to Category C in ISO 7730. The overall discomfort was related to the OTS cooler than thermal neutrality. The LTSs of body segments fluctuated within the range of −0.7 – 0.7. Among the body segments, the head had the most significant influence on OTC, and followed by the feet. The percentage of dissatisfied due to discomfort of warm head and/or cold feet (PD) might exceed 10%, which was mainly resulted from the discomfort risk of cold feet. The relationship between PD and LTS of the feet indicated that with LTS of the feet higher than −0.5, the PD could be below 10%. With stratum ventilation for winter heating, the air movement was acceptable with draft rate less than 20%. However, the humidity environment remained to be improved by additional measures.

Thermal-comfort evaluation of and plan for public space of Maling Village, Henan, China

The thermal environment of village public space affects the comfort of people ' s outdoor activities, and then affects the willingness of residents to outdoor activities, which has an important impact on the villagers' quality of life. Previously published studies of thermal comfort mostly focused on the evaluation of thermal comfort index, few studies on the application of thermal comfort planning. The study was carried out in Maling Village, Changdai Town, Mengjin County, Luoyang City, Henan Province, China. Square, street, green space were chosen as three typical public spaces where thermal comfort indexes were measured by questionnaire survey and field measurement during summer. Subsequently, the village's microclimate environment was simulated with ArcGIS 10.6 and ENVI-met. The results indicate that during the summer, the influences of temperature, solar radiation, wind speed, and relative humidity on the subjective comfort conditions of the outdoor environment gradually decreased. The spatial form of village has an important influence on thermal comfort. Finally, based on the results, this study put forward the thermal comfort process and planning scheme of the village outdoor space.

Comparison study of thermal comfort and energy saving under eight different ventilation modes for space heating

Comparison study of thermal comfort and energy saving under eight different ventilation modes for space heating

Thermal Comfort Performance of Naturally Ventilated Royal Malaysian Police (RMP) Lockup in Hot and Humid Climate of Malaysia

Thermal comfort performance of three vacant naturally ventilated Royal Malaysia Police (RMP) case study lockups (LK1 in Penang, LK2 in Melaka & LK3 in Kuala Lumpur) was measured during monsoon change period from Northeast Monsoon to Southeast Monsoon. According to NGO’s report and previous studies, the lockups condition is very poor and hot which contribute to discomfort among detainees. The objectives of the study are to investigate thermal comfort performance of the lockups based on four environmental parameters (Ta, Tr, Va, & RH) through physical measurement, to predict thermal comfort performance based on operative temperature (To) and neutral operative temperature (Tneutop), and to compare the results with thermal comfort criteria recommended by ASHRAE 55 standard and previous thermal comfort studies in hot and humid climate. The results show that To and Tneutop reading of LK1 is exceeding the maximum range recommended by ASHRAE 55 and previous studies by 2% to 8% (To) and 1% (Tneutop) which categorizing LK1 condition as hot. This is mostly due to high hot airflow brought through an ineffective window opening. The results will be used as reference for improvement towards some aspects such as window opening, building finishes materials, space volume and building orientation in future lockup design.

Biomimicry-Based Strategies for Urban Heat Island Mitigation: A Numerical Case Study under Tropical Climate.

In recent years, demographic growth has caused cities to expand their urban areas, increasing the risk of overheating, creating insurmountable microclimatic conditions within the urban area, which is why studies have been carried out on the urban heat island effect (UHI) and its mitigation. Therefore, this research aims to evaluate the cooling potential in the application of strategies based on biomimicry for the microclimate in a historical heritage city of Panama. For this, three case studies (base case, case 1, and case 2) of outdoor thermal comfort were evaluated, in which the Envi-met software was used to emulate and evaluate the thermal performance of these strategies during March (highest temperature month) and October (rainier month). The strategies used were extracted from the contrast of zebra skin, human skin, evaporative cooling, and ant skin. The results showed a reduction of 2.8 °C in the air temperature at 11:00, the radiant temperature decreased by 2.2 °C, and the PET index managed to reduce the thermal comfort indicator among its categories. The importance of thinking based on biomimicry in sustainable strategies is concluded; although significant changes were obtained, high risks of discomfort persist due to the layout and proximity of the building.

Cooling strategies for thermal comfort in cities: a review of key methods in landscape design.

Under the climate change scenario, the negative impacts of urban heat island (UHI) will exacerbate due to unsustainable urban planning and human activities. Thermal comfort has close relationships with UHI in urban areas. This paper is based on the studies of urban heat island, thermal comfort, microclimate, and urban planning in cities in the recent decade, combined with a method of research into design. The key topics include vegetation and water conditions, the albedo of materials, and urban morphology. By the comparative case studies in landscape projects, the results further reveal that the density of tree canopies, the natural structure and density of ground cover, the form of water features, the color and texture of materials, and the scale of shading structures have different cooling effect and performance in outdoor thermal comfort improvement with specific features in the landscape design. It is also found that there are some external conditions that can influence design determinations in real practices. The purpose of this study is to provide theoretical research methods and evaluation of thermal comfort landscape design elements and to provide guidance for future sustainable city research and landscape design.

A Case Study on the Assumption of Mean Radiant Temperature Equals to Indoor Air Temperature in a Free-Running Building

Thermal comfort is basically affected by environmental (mean radiant temperature, indoor air temperature and relative humidity and air velocity) and personal parameters (clothing value and activity level). Mean Radiant Temperature is the most complicated parameter among all thermal comfort parameters due to the difficulty of measurement and calculation processes. Calculation methods are not preferred by the researchers because of the complexity of obtaining angle factors while the measurement methods require very expensive devices such as globe thermometers and radiometers. On the other hand, assumptions are commonly used in thermal comfort studies because of their simplicities. One of the most frequently used assumptions expresses the equality of mean radiant temperature to indoor air temperature. However, the accuracy of this assumption needs further experimental research in order to evaluate thermal comfort, especially in free-running buildings. To this aim, this study proposes to determine the accuracy of the assumption of mean radiant temperature equals to indoor air temperature in a free-running building where Adaptive Thermal Comfort approach is applied in summer condition. Environmental parameters are measured via objective sensors, while adaptive thermal comfort is assessed by a software program. The statistical results show that there are significant deviations between two parameters in summer conditions for a free-running building.

Evaluation of thermal comfort and air quality of low-income housing in Kampala City, Uganda

This paper presents the results of thermal comfort and air quality studies in naturally ventilated residential buildings in Kampala City, Uganda. Questionnaire surveys were used for obtaining occupant subjective thermal sensation votes. Indoor and outdoor measurements for air temperature (Ta), Mean Radiant Temperature (MRT), relative humidity, air speed, and air quality were done for seven buildings over fifteen days during the month of June 2019. DesignBuilder software was used to develop the reference building model and to simulate strategies for improvement of thermal comfort. Survey results showed that 67.8% of the respondents were comfortable with the indoor thermal environment. The indoor air temperature range was 22.7°C - 27.9°C which lies within the 80% acceptable limits set by ASHRAE 55. The measured indoor MRT range was 24.24°C - 25.57°C. Measured levels of indoor PM2.5 were double the World Health Organization recommended limits, while the levels of PM10 were thrice the recommended limits of ASHRAE 62.1. The CO2 concentrations were within the limits set by ASHRAE 62.1. The developed model predicted comfortable indoor conditions with a temperature range of 23.6°C - 25.3°C based on the 80% acceptable limits set by ASHRAE 55. The results show that majority of occupants preferred cooler temperatures during the day which is justified by the use of adaptive measures to obtain thermal comfort.

Thermal comfort standards in the Middle East: Current and future challenges

Cooling energy demand has increased three-fold in the Middle East (ME) over the last 30-years. This is driven by the need to maintain thermal comfort in an extremely hot climate, and supported by rising incomes, falling costs of air-conditioning and growth in the number of buildings. The definition of thermal comfort in these buildings is drawn from “international” standards, which, though empirically derived, have no basis data from this region. Hence, we ask, to what extent do indoor conditions in the ME fall within the standards recommended range of thermal comfort, and when they do, whether they are found to be comfortable by their occupants. We present the first large-scale study of thermal comfort in the ME, consisting of two approaches: (i) a meta-analysis of data from existing studies, (ii) independent field data covering four countries representing 27% of the region's population, 31 air-conditioned buildings of different types, including “green” buildings, and 1,101 subjects. The meta-analysis demonstrates that current thermal comfort standards fail to predict thermal sensation of 94% of occupants. Our own data show that, while indoor conditions are within standards-recommended ranges 58% of the time, only 40% of occupants find these conditions acceptable. We find evidence of overcooling in summers, with 39% occupants expressing cold discomfort. Computer models suggest that this is likely to have increased annual cooling energy demand between 13% and 20%, compared to non-overcooled conditions. These results suggest the necessity of localised thermal comfort standards that mitigate excess cooling energy demand, without compromising occupant thermal comfort.

Adaptive thermal comfort study of workers in a mini-industrial unit during summer and winter season in a tropical country, India

Providing a comfortable thermal environment to workers for better health and productivity is one of the necessary conditions for sustainable industrial development. However, there is a dearth of field studies on the thermal comfort status and adaptation of workers in naturally ventilated industrial buildings across the world. Therefore, an adaptive thermal comfort field study in a mini-industrial unit factory, located in the composite climate of India, was conducted in the hot summer and cold winter seasons. Overall, 1276 valid subjective responses were collected from 325 factory workers during the field measurements and survey. We found a seasonal comfort temperature variation of more than 9.5°C with a mean comfort temperature of 32.2°C. The mean preferred temperature was observed about 2.5°C lower than their mean comfort temperature. The adaptive comfort relation suggested that surveyed factory workers had a high thermal adaptation owing to the combined effect of behavioural adjustments and elevated airspeed. A logistic regression analysis was carried out to predict the fan use behavior by the workers during the hot summer season. Since the study duration also lies in the COVID-19 pandemic period, an effort has been made to quantify the psychological and behavioural changes of workers due to the COVID-19 pandemic situation at their workplace through a questionnaire-based study.

Study of Thermal Comfort in Traditional House Buildings (Case Study: Simalungun Traditional House)

Abstract. Traditional houses were formed over a long period and are believed to be hereditary responsive to the surrounding physical and socio-cultural environment. Traditional Architecture is a building whose shape, decoration and method of implementation are passed down from generation to generation. Traditional architecture is a reflection of the values and culture that the community has interpreted. The adaptation of residents in the house is carried out by optimizing the positive potential of the surrounding environment and minimizing disturbances related to the comfort of living. The research problem is how the level of thermal comfort in the traditional house of Simalungun. The purpose of this study is to analyze the thermal comfort of the study object of the Simalungun traditional house. To determine the thermal conditions inside and outside the building, Measurements of temperature and humidity were carried out. Measurement data were analyzed and compared with Ecotech simulation data. The results of research carried out directly and simulating using Ecotech. This Simalungun traditional house can be categorized as having optimal comfort in terms of its physical physiological aspects and simulate using Ecotech simulations. As for the benefits of the research, it is hoped that it can provide knowledge about the thermal comfort of traditional houses, especially the traditional houses of Simalungun.

Thermal comfort perception in naturally ventilated affordable housing of India

ABSTRACT Indoor thermal comfort is critical to building sustainability besides improving occupants’ health, well-being and productivity. However, the applicability of the existing comfort standards within different climatic conditions and contextual settings is often in question. This study presents the findings from a longitudinal thermal comfort study conducted in low-income affordable housing in Mumbai, India. Surveys were conducted in three distinct seasons within a warm–humid climate. The linear regression method yielded a mean neutral temperature of 28.3°C and a wide comfort band ranging from 24.6°C to 32.2°C indicating high thermal adaptation among the occupants. The preferred temperature was found to be 26.3°C. Adaptive comfort standards, ASHRAE and the National Building Code of India prescribed a narrow range of comfort and were ineffective in predicting comfort conditions within affordable housing units. The role of income in shaping comfort expectations was established, lending support to the economic dimension of comfort. The results would be helpful in providing design recommendations for the future affordable housing stock and the development of an adaptive comfort model for vulnerable low-income communities.