Thermal Comfort Index Research Articles

Investigating Thermal Comfort Indices in Relation to Clothing Insulation Value: A survey of an outdoor space in Tehran, Iran

Investigating Thermal Comfort Indices in Relation to Clothing Insulation Value: A survey of an outdoor space in Tehran, Iran

Architectural design strategies based on climatic zoning and thermal comfort indices (Case study: Qazvin)

Architectural design strategies based on climatic zoning and thermal comfort indices (Case study: Qazvin)

The Impact of Urban Roughness on Outdoor Thermal Comfort in Hot Arid Climate

The proportion of the world's population living in cities is rapidly increasing, presenting new challenges to the urban environment and quality of life. Among these challenges is the urban environment's impact on residents' outdoor thermal comfort, which can affect their health and well-being. Urban roughness, which includes building and street heights, has a significant impact on the thermal environment of urban areas. Changes in these factors cause variations in temperature distribution, wind speed, and humidity, which affect how people perceive thermal conditions. The research problem is the effect of urban roughness on outdoor thermal comfort in hot arid climate, specifically the height of buildings and the density, for a case study in (Al-Bab Al-Sharqi) in Baghdad city. Measurement method that employed the computer programs (Rino8 and Grasshopper) to calculate the thermal comfort index (UTCI) and its impact on various climatic variables. The findings revealed that the thermal comfort index and the climatic factors associated with it vary depending on the configuration of buildings.

Evaluating and enhancing the applicability of thermal comfort indices in diverse outdoor environments using Bayesian and random forest regression

This research aims to evaluate and improve the applicability of three commonly utilized thermal comfort indices—standard effective temperature (SET), physiological equivalent temperature (PET), and universal thermal climate index (UTCI)—in outdoor environments. The study was conducted in four typical spaces of a university in Xi’an, China, covering different environmental settings: East Lake (Place 1), tree-lined path (Place 2), campus playground (Place 3), and campus square (Place 4). A total of 322 volunteers participated by completing a subjective sensory questionnaire in randomized environments, and on-place meteorological data were collected. The study yielded three primary findings. First, the tree-lined path (Place 2) was identified as the most comfortable outdoor space on the university campus during summer, whereas East Lake (Place 1) was the least comfortable. Second, substantial residuals were observed for SET, PET, and UTCI across different places when assessing the thermal comfort variations experienced by the subjects. Third, Bayesian regression and random forest regression were employed to analyze and adjust the thermal comfort indices. The comparative study found that after correction, the model explanatory power of PET increased by up to 20%, with the standard deviation of residuals decreasing by up to 0.314 and MSE decreasing by up to 0.1912. The model explanatory power of SET increased by up to 31.2%, with the standard deviation of residuals decreasing by up to 0.3867 and MSE decreasing by up to 0.3012. For UTCI, the model explanatory power increased by up to 10.5%, the standard deviation of residuals decreased by up to 0.2215, and the MSE decreased by up to 0.1002.

Park thermal comfort and cooling mechanisms in present and future climate scenarios

Extreme heat is Australia’s most perilous natural hazard, and increasing urban temperatures due to climate change are a growing concern. Consequently, there is growing interest in developing nature-based solutions (i.e., greenery and vegetated surfaces) to cool urban areas. Appropriately designed urban parks are anticipated to be crucial for maintaining thermal comfort as temperatures rise. The two main diurnal cooling mechanisms of urban parks are shade provision and vegetation transpiration. However, limited studies have examined the cooling performance of vegetation through transpiration, especially in the southern hemisphere. This study addresses this gap by examining the microclimatic conditions, cooling benefits, and thermal performance of a typical neighbourhood park in Perth, Western Australia, with a focus on the cooling performance of vegetation through shade and transpiration. Present and future microclimates were modelled and simulated for average and hottest summer days based on 25 years of local weather data and projections for 2090 under the Representative Concentration Pathway (RCP) 8.5 scenario. The findings reveal that trees provided diurnal cooling benefits for park users by lowering the Universal Thermal Comfort Index (UTCI) by up to 17°C, with this benefit persisting in projected 2090 conditions. This cooling benefit was predominantly achieved through shade provision, with marginal contributions from transpiration. Additionally, on hot days, as leaf temperature exceeded 30°C, increased stomatal resistance led to reduced transpiration. Therefore, more attention must be paid to transpiration cooling limits due to stomatal closure during hot hours to improve cooling performance in park design. Moreover, comparing different plant species’ behaviour and adaptability on hot days is crucial, especially in future climatic conditions.

Significance analysis and evaluation of the impact of a new sustainable ecosystem on the microenvironment of multi-level thermal humidity

Active living walls represent sustainable green technology that improves indoor thermal environment. However, the improvement effect of active living walls in these environments still needs to be further explored, especially with regard to humidity. This study aims to effectively improve the indoor thermal humidity microenvironment of residential buildings, a new sustainable ecosystem (NSES) was developed. NSES integrates plants, spray cooling, and a fan, offering four operation modes, all controlled through intelligent monitoring based on the indoor conditions. Under the working scale of limited space in the microenvironment, evaluating system performance has solved the problem of thermal comfort. In addition, subjective questionnaires are used to evaluate human thermal comfort indicators. The results indicate that (1) Mode 1 exhibits the best performance on the microenvironment throughout the season at a distance of 0.5 m horizontally and 1.1 m vertically from NSES; as the vertical height and horizontal distance increase, performance gradually weakens. (2) Under the conditions of 0.5 m horizontal distance and 1.1 m vertical height, NSES has the best improvement effect on the microenvironment on sunny summer days; an average temperature decrease of 5.6 °C and an average humidity increase of 27.5 % were achieved. (3) NSES can improve human comfort, with thermal comfort zones ranging from 22.4 to 24.3 °C in autumn, and 22.4–23.8 °C in spring. These results highlight the potential value of NSES in improving the microenvironment and enhancing human thermal comfort. This study emphasizes the importance of NSES in appropriately selecting distance, height, season, and climate.

Detailed thermal environment classification of high geothermal tunnel based on thermal comfort indices

High temperature and high humidity in geothermal tunnels pose significant risks to the well-being of construction workers. This study aims to establish critical environmental thresholds to protect workers in these challenging conditions. Field tests were conducted in a high geothermal tunnel in southwest China, continuous measuring parameters such as dry bulb temperature, relative humidity, wet bulb globe temperature (WBGT), skin temperature, and heart rate. The collected data were analyzed, leading to the development of a nonlinear programming mathematical model. This model enabled a systematic classification of the tunnel's environmental conditions and the calculation of threshold values for various environmental parameters. Furthermore, critical thresholds for heat stress indicators such as the discomfort index (DI), heat index (HI), and relative strain index (RSI) were determined. The study categorized the tunnel's hot and humid environment into five distinct zones: comfortable zone, general comfortable zone, safety zone, heat tolerance zone, and danger zone. The findings indicate that in this geothermal tunnel, the comfort zone thresholds are 26 °C for dry bulb temperature, 30 % for relative humidity, and 20 °C for the WBGT index. The safety zone thresholds are 37 °C, 64 %, and 32 °C, while the danger zone thresholds are 43 °C, 81 %, and 40 °C, respectively. For heat stress indices, the safety thresholds for DI, HI, and RSI are 25.42 °C, 26.31 °C, and 0.28, while the danger thresholds are 28.59 °C, 35.30 °C, and 0.38, respectively. This research provides essential insights for safeguarding the health of construction workers operating in high geothermal tunnel environments.

Health risk assessment of residential overheating under the heat waves in Guangzhou

During extreme heatwave events, indoor overheating caused by power outages poses a significant threat to human health, especially for low-income groups exposed to hot and humid conditions for extended periods. However, currently, the definition and quantification standards for indoor overheating are not well-defined, and relying solely on thermal comfort indicators is insufficient to accurately assess the health risks associated with indoor overheating. This study proposes the use of maximum heat index (HImax) and heat index hazard hours when the heat index exceeds the caution level (HIHHCaution) to assess the health risk of indoor overheating. Taking various types of residential buildings in Guangzhou as examples, the study employs field surveys, simulation analysis, and statistical regression to analyze the impact of power outages during heatwaves on the indoor thermal environment and key human thermal physiological parameters, thereby establishing the basis for measuring indoor overheating and reference thresholds for assessing heat health risks. The results indicate that for young adults and the elderly, HIHHCaution exceeding 1174 °C·h and 850 °C·h respectively, or HImax nearing 55 °C, are likely to result in heat-related illnesses. In Guangzhou, most urban village housing with poor insulation cannot withstand the risk of power outages lasting more than a day during heatwaves, while old housing and commodity housing that meets the energy-efficiency standards of different periods still face varying degrees of indoor overheating risk. The findings enhance understanding of indoor overheating health risks and provide a scientific basis for strategies to improve living environments during heatwaves.

Microclimate analysis of Ganga riverfront in Patna: spatial form perspective

ABSTRACT The investigation in this research scrutinizes the influence of spatial form factors on thermal comfort along the Ganga riverfront trail during the spring season. Understanding how spatial form factors impact local climate parameters and PET values is crucial for optimizing thermal comfort in urban waterfronts. The research addresses the need to improve thermal comfort in rapidly urbanizing areas through strategic urban design. Data were collected from eight measurement points along the riverfront, analyzing Air Temperature (Ta), Relative Humidity (RH), Wind Velocity (v), Surface Temperature (Ts), Global Radiation (G) and Mean Radiant Temperature (Tmrt). The study employs a combination of field measurements and statistical analysis to assess the correlation between spatial form factors and thermal comfort indicators. Findings reveal that lower building height (Hb) values are associated with more favorable thermal comfort conditions, while higher Hb negatively impacts thermal comfort. The study also highlights that building spacing (ADb) influences thermal comfort, with findings contrasting those from composite climates, suggesting a need for context-specific design strategies. The research underscores the significant role of Ta and v in shaping Physiological Equivalent Temperature (PET), aligning with previous studies in diverse urban contexts. The results emphasize the critical impact of spatial form on microclimate and thermal comfort, informing urban design and planning to enhance livability along the Ganga riverfront. This study contributes to the field by providing empirical evidence and practical insights for developing thermally comfortable walking trails.

Evaluating thermal comfort indices for outdoor spaces on a university campus

This study evaluates the applicability of three thermal comfort indices—Physiologically Equivalent Temperature (PET), Standard Effective Temperature (SET), and Universal Thermal Climate Index (UTCI)—in various outdoor environments on the campus of Xi’an University, China. Meteorological data were collected on sunny days using a portable weather station at a height of 1.5 m, and subjective questionnaires were administered to 25 healthy university students over three months to gather Thermal Sensation Votes (TSV) and Thermal Comfort Votes (TCV). The study was conducted at four distinct outdoor locations: a lakeside area (Location 1), a shaded path (Location 2), a sports field (Location 3), and a plaza (Location 4). PET, SET, and UTCI values were calculated from the collected data using Rayman software. The analysis revealed significant differences in thermal comfort across the four locations, with the highest proportion of subjects feeling hot at the sports field (54.4%) and the highest proportion feeling cold at the lakeside (39%). The shaded path had the highest proportion of subjects feeling comfortable (79.4%), while the lakeside had the lowest (60.1%). The results indicated that SET underestimated thermal sensation at Locations 1, 3, and 4, necessitating calibration. PET was suitable for Locations 2, 3, and 4 but failed to reflect the thermal sensation at Location 1 due to prolonged sun exposure. In contrast, UTCI demonstrated applicability across all locations. To enhance accuracy, revised indices SET’ and PET’ were formulated using the mean-median method, providing more precise thermal comfort assessments. These findings underscore the limitations of SET and PET under specific conditions and highlight the robustness of UTCI, offering valuable insights for urban planning and design aimed at improving outdoor thermal comfort and well-being.

Personalized low-cost thermal comfort monitoring using IoT technologies

Thermal comfort plays an essential role in the well-being and productivity of occupants. Typically, thermal comfort is assessed either through surveys completed by building occupants or through sensor data that is analyzed using thermal comfort models. Automating comfort surveys and data collection processes reduce the risk of information loss, providing more accurate and personalized thermal comfort assessments over longer periods of time. To this end, this paper presents the design and implementation of a thermal comfort monitoring system consisting of low-cost hardware components and using IoT technologies. The system consists of intelligent wireless sensor nodes that collect and process environmental data, a portable main station that integrates and stores data, and a digital survey that provides feedback from building occupants. To ensure accuracy, the low-cost hardware components of the intelligent sensor nodes are calibrated in a climate chamber, using high-precision sensors for reference. After calibration, the system is deployed in a field test where several intelligent sensor nodes collect environmental data in an office, while occupants complete the digital thermal comfort survey. In addition, thermal comfort indexes are computed by the intelligent sensor nodes and compared with the feedback of each building occupant. The results indicate that the low-cost thermal comfort monitoring system successfully collects and integrates thermal comfort data from the intelligent sensor nodes and the digital survey, being able to create personalized thermal comfort profiles. In future work, the system can be used in large-scale thermal comfort surveys, to develop personalized thermal comfort models and to control personalized comfort systems.

Study of indoor local thermal comfort for impinging jet ventilation combined with ductless personalized ventilation under different cooling loads

Excessive temperature stratification and draught are two prominent drawbacks for impinging jet ventilation (IJV). Using IJV together with ductless personalized ventilation (DPV) (i.e., IJV + DPV) has been proved to be an effective way to reduce temperature stratification, but the draught rate around occupant would be increased. In the current work, an in-depth study on the characteristics of indoor local thermal comfort for IJV + DPV operating with different scenarios is done. Predictive models for the local thermal comfort indicators are developed to optimize the operating parameters (including supply velocity of IJV (Vs) and intake airflow rate of DPV (Df)) with different room cooling loads (Q). The results show that the application of IJV can be extended to spaces with high cooling loads (e.g., larger than 60 W/m2) by using together with DPV, but the risk of thermal discomfort increases. To avoid local thermal discomfort, the combination relationship between Vs and Df should be properly matched and this relation becomes more stricter with the increase of Q. It also obtains that the maximum cooling load that IJV + DPV can eliminate is less than 170 W/m2. At last, to ensure the IJV + DPV create a good local thermal comfort environment, design chart about the feasible ranges of Vs and Df are established for different values of Q. On the whole, the current study not only can provide a basis for the application of IJV + DPV in spaces with high cooling load, but also can provide theoretical guidance for the operation control and optimization design of the IJV + DPV.

Atmospheric Conditions Related to Extreme Heat and Human Comfort in the City of Rio de Janeiro (Brazil) during the First Quarter of the Year 2024

This study aims to investigate the atmospheric conditions and human thermal comfort related to extreme heat in Rio de Janeiro during the first quarter of 2024. The dataset includes meteorological data from the A636-Jacarepaguá station of INMET and seven stations from the Alerta Rio system. Weather types were classified using principal components analysis (PCA) and cluster analysis (CA). Additionally, three thermal comfort indices were calculated: the heat index (HI), physiologically equivalent temperature (PET), and modified PET (mPET). Five groups of surface weather types were identified, with two being more frequent and associated with extreme heat events. These two groups accounted for over 70% of the days in all months. Critical thermal sensation values were found, particularly at the Guaratiba station, where the daytime HI exceeded 60 °C, and at the Riocentro station, where the nighttime HI surpassed 40 °C. The HI showed a greater range and variability compared with the PET and mPET, highlighting the importance of investigating microclimatic factors which intensify urban heat in central and coastal areas and cause daytime overheating in more distant regions like Guaratiba. This study emphasizes the need for detailed investigation into microclimatic factors and their public health implications, especially in areas with high tourist activity and vulnerable populations.

Assessment of the effects of heat stress on the production of dairy cows by using two comfort thermal indices in Southern Chile

Heat stress has been recognized as a serious problem in dairy farms around the world due to the increasing heat waves and higher genetic potential of dairy cows. In Chile, milk production is concentrated in the southern regions of the country, where animals graze all year around, consequently being exposed directly to environmental conditions. Nevertheless, there are few studies conducted in Chile that have evaluated at the commercial level the impact of heat stress on milk production. The aim of this study was to assess the effects of summer conditions, across periods, on the milk production of cows at different stages of lactation in a dairy farm located in Southern Chile. Daily meteorological and milk yield records of three summers from a dairy farm were collected to characterize the relationship between two thermal stress indices and milk yield. The thermal comfort indices used were the comprehensive climate index (CCI), and the adjusted temperature humidity index (THIadj). The average values of CCI and THIadj were dependent on the period (P < 0.0001) with maximum CCI of 40.2 °C, 31.7 °C, and 27.5 °C for the 2012–2013, 2015–2016, and 2016–2017 periods, respectively. A similar response was recorded when THIadj was used (85.5, 78.0, and 73.9, respectively). In the 2012–2013 summer, 44.4% of the days presented conditions of heat stress (CCI ≥23), a value that fell to 26.7% in the summer of 2015–2016 and only 5.6% in the 2016–2017. On the opposite, when the THIadj was used, these values were 50%, 48.9%, and 5.6%, respectively. In conclusion, both comfort thermal indices are good tools to determine the risk of thermal stress in dairy cows, with a large variation between the three summer periods but also between indices. Likewise, cows in the early and mid-lactation periods are more affected in terms of milk yield.

Exploring the effects of landscape interventions on outdoor thermal comfort using digital simulation

Abstract The assessment of outdoor thermal comfort plays an important role in design decisions and encourages better planning and development of outdoor environments. This study explores the potential effects of landscape interventions on outdoor thermal comfort, testing two thermal comfort indicators on a selected hospitality development. Results are crucial factors to consider as the success of hospitality developments and its outdoor spaces are dependent on how visitors perceive and interact with them. Digital simulations were conducted using Rhinoceros software and the Grasshopper tool to produce heat maps. For the purpose of the study, two sets of simulations were developed to examine changes in the Universal Thermal Climate Index (UTCI) and Incident Radiation of the site – a) buildings alone and b) with landscape elements. As a result, UTCI with landscape intervention decreased by 2°C while Incident Radiation is significantly lower throughout spaces provided with shading elements. Results of UTCI simulations still deliver strong heat stress to occupants, while Incident Radiation has considerably improved with landscape interventions. The provision of shading elements helped lessen solar radiation penetrating the site, thus improving the thermal comfort of users. Wind velocity showed minimal effects on perceived heat based on the UTCI assessment scale. Nonetheless, improvement in the planning and orientation of buildings and strategic provision of demountable sun shading elements in future developments are recommended to allow better air circulation.

Sustainable Thermal Comfort by Age Group in Shopping Malls: Multi-Year Winter Surveys in a Severely Cold Region

The current Chinese standard utilizes a single thermal comfort index guide to regulate indoor parameters for public buildings. However, heating, ventilation, and air conditioning (HVAC) settings often do not align with the occupant’s needs. To address this, a 2-year winter field survey was conducted in four large-scale shopping malls across severely cold regions of China, considering the complex age structure of mall visitors. Physical environmental parameters were measured, and a subjective questionnaire yielded 1464 valid responses. Neutral temperatures for different age groups were 17.4 °C for children (0–12 years of age), 19.3 °C for early youth (13–24), 20.0 °C for mature youth (25–44), and 23.3 °C for middle-aged adults (45–59). The limit of the 80% acceptable temperature range for the children and early youth was lower than the current Chinese GB 50736 standard, suggesting that HVAC temperatures for the corresponding shopping malls can be appropriately reduced for the target consumer groups. Significant differences occurred between customers’ demand for thermal environments in shopping malls and various standards. These findings provide valuable insights into energy-efficient architectural design and operational management of shopping malls in the Shenyang area, promoting the sustainable development of human thermal comfort environments.

Air Monitoring in Operating Rooms: Results from a Comprehensive Study in the Campania Region

Ensuring air quality in operating rooms is crucial for the health and safety of healthcare professionals and patients. This study, focused on 141 operating theatres in the Campania Region from 2015 to 2022, highlights the importance of air monitoring in operating rooms. Microclimatic parameters, air exchanges, thermal comfort indices, air pressure differences, and anesthetic gas concentrations were measured using standardized procedures. Results indicate that 19% of microclimatic checks exceeded acceptable limits, with significant non-compliance in air velocity (0.01–0.04 m/s, mean 0.03 m/s) and air changes (1–14 h−1, mean 6 h−1). Additionally, levels of anesthetic gases such as nitrous oxide (54.7–197.31 ppm, mean 142.92 ppm) and sevoflurane (2.05–19.45 ppm, mean 5.90 ppm) frequently exceeded recommended exposure limits, raising health concerns. These findings underscore the importance of rigorously adhering to environmental standards and continuously monitoring for optimal conditions in operating rooms. The study also stresses the necessity of ongoing education and training for healthcare personnel on preventive measures to reduce risks. In conclusion, maintaining optimal environmental conditions not only safeguards the comfort and safety of healthcare professionals and patients, but also improves team productivity and clinical outcomes. The study advocates for regularly updating national guidelines and rigorously enforcing safety protocols in healthcare facilities.

Reduction of Heating Energy Demand by Combining Infrared Heaters and Infrared Reflective Walls

We study the potential of infrared (IR) heaters in combination with IR reflective walls to reduce heating energy demand in buildings. Using IR heaters increases radiant temperature. Combined with IR reflective walls, less radiant heat is absorbed by the surrounding walls, and more is reflected to and absorbed by the occupants. This allows for lower air temperatures while maintaining constant thermal comfort. Lower air temperatures result in heating energy savings. In simulations, we examine the impact of four parameters on the thermal comfort indicator Predicted Mean Vote (PMV): wall temperature, inlet air temperature, IR heater power, and IR emissivity of the walls. To reduce the number of data points needed, we use a Central Composite Design for the layout of the simulation plan. The results show that the PMV can be changed from 0.15 to 1.16 only by lowering the emissivity of the surrounding walls from 0.9 to 0.1. At high IR heater power and at low wall temperature the impact of the emissivity on the PMV becomes larger. From the simulation data, we derive a response surface function to determine the required IR heating power for any given room conditions, which could be used for automated IR heater control.

Evaluation of Thermal Comfort Online Simulation Tools Usage Through Distance Education Process in an Applied Graduate Course

Through Covid 19 pandemic, education field has experienced mandatory transition to distant education. The case study held in Indoor Comfort Management postgraduate course. In order to examine how direct sunlight affects the adaptive thermal comfort of the user, simulations were made with online tools to evaluate thermal comfort within the scope this course at Yaşar University. The SolarCal and ComfTool of CBE online tools are used. This article aims to question the contribution of online simulation tools to education via a questionnaire given to students to grasp aspects of adaptive thermal comfort. The use of these aforementioned online tools and formulas can enrich studies and draw conclusions in limited facilities for professionals especially for architectural and engineering industries. The results of the survey will be analyzed to ensure the applicability of such a methodology in similar learning environments for easy understanding of the various adaptive thermal comfort indices at once.

Strategic tree placement for urban cooling: A novel optimisation approach for desired microclimate outcomes

Trees are crucial elements for improving urban microclimates by providing cooling through shading, evapotranspiration, and windbreaks. To maximise their cooling effects, it is essential to strategically position the trees in optimal locations. However, research on optimising tree location and its impact on microclimates is limited owing to computational challenges and costs. This study introduces a novel method that employs three optimisation algorithms—i.e., Non-dominated Sorting Genetic Algorithm II (NSGA-II), Particle Swarm Optimisation (PSO), and Ant Colony Optimisation (ACO)—to identify the optimal locations for trees in urban environments to enhance urban thermal comfort. The research methodology involves simulating microclimate responses to tree placements optimised by each algorithm and assessing the results based on urban thermal comfort. The results underscore the efficacy of optimised tree locations, demonstrating that optimising tree locations can significantly reduce the Universal Thermal Comfort Index (UTCI) in urban areas. Furthermore, the findings suggest that the clustering of tree canopies has a compounding impact on these cooling benefits in urban areas. Notably, all three algorithms significantly improved UTCI. PSO demonstrated the rapid identification of effective tree configurations. However, ACO provided the most substantial reduction in air temperature, highlighting its potential as an effective tool for urban cooling. While efficient, NSGA-II plateaued earlier, suggesting its utility in scenarios where timely solutions are crucial.