Outdoor Thermal Comfort Index Research Articles

Analysis of the Effect of Outdoor Thermal Comfort on Construction Accidents by Subcontractor Types

The impact of climate on construction site safety varies significantly depending on subcontractor types due to the diverse nature of workplaces and work methods. This study introduces a novel approach by categorizing construction work according to subcontractor types and assessing accident risk probabilistically through the Physiologically Equivalent Temperature (PET), an outdoor thermal comfort index. Additionally, a Hidden Markov Model (HMM)-based clustering methodology was proposed to classify new groups using PET and accident probability. This study proceeded in the following sequence: (i) collection and classification of data, (ii) PET calculation, (iii) calculation of accident probability, and (iv) clustering and Pearson correlation coefficient analysis. As a result of clustering, each group was classified according to the workplace. Groups 2 and 3 demonstrated a strong positive correlation between accident probability and PET, with correlation coefficients of 0.837 and 0.772, while Group 1 exhibited a moderately positive correlation of 0.474. This study quantitatively evaluated the impact of climate on workers for each subcontractor type using PET, an outdoor thermal comfort index for construction work, and accident probability, resulting in the identification of new groups. The findings of this study may serve as novel benchmarks for safety management in construction worker safety based on PET.

Review on Gaps and Challenges in Prediction Outdoor Thermal Comfort Indices: Leveraging Industry 4.0 and ‘Knowledge Translation’

The current outdoor thermal comfort index assessment is either based on thermal sensation votes collected through field surveys/questionnaires or using equations fundamentally backed by thermodynamics, such as the widely used UTCI and PET indices. The predictive ability of all methods suffers from discrepancies as multi-sensory attributes, cultural, emotional, and psychological cognition factors are ignored. These factors are proven to influence the thermal sensation and duration people spend outdoors, and are equally prominent factors as air temperature, solar radiation, and relative humidity. The studies that adopted machine learning models, such as Artificial Neural Networks (ANNs), concentrated on improving the predictive capability of PET, thereby making the field of Artificial Intelligence (AI) domain underexplored. Furthermore, universally adopted outdoor thermal comfort indices under-predict a neutral thermal range, for a reason that is linked to the fact that all indices were validated on European/American subjects living in temperate, cold regions. The review highlighted gaps and challenges in outdoor thermal comfort prediction accuracy by comparing traditional methods and Industry 4.0. Additionally, a further recommendation to improve prediction accuracy by exploiting Industry 4.0 (machine learning, artificial reality, brain–computer interface, geo-spatial digital twin) is examined through Knowledge Translation.

Ambient temperature modelling from surface characteristics and associating urban morphology with thermal discomfort

Urban heat island assessment is of paramount importance when monitoring microclimate changes, increased heat stress, mortality and energy consumption. Simply analysing land surface temperature patterns for human comfort and health assessment is often inadequate. In this study, we attempt to resolve this inadequacy with ambient temperature modelling from multiple surface characteristics for a tropical megacity. A 336 datapoint‐based multilinear regression model was formulated to predict the maximum summer air temperature with a mean absolute error of 0.694°C. Specific locations of critical thermal environments were demarcated with Getis‐Ord statistic. Based on our results, extreme hotspots covered 10.53 per cent of the city on a daily basis at 99 per cent confidence level. The application of an outdoor thermal comfort index highlighted the existence of very strong heat stress zones over 14.67 per cent of the study area. The air temperature hotspots were verified with intra‐urban variation in carbon sequestration. This environmental parameter was used to strengthen the observed results since, carbon sequestration directly links urbanization with degradation of thermal environments. Further, five urban morphological parameters were analysed to conclude that building density and height were the most significant urban design factors leading to increased air temperature. Simultaneous local climate zone mapping depicted that heat islands were dominated by mid and high‐rise built‐up areas, of which 68.44 km2 of that area is suitable for vertical and roof gardening. Another 33.29 km of road stretch was delineated within low‐rise built‐up areas with scope for green landscaping to improve urban sustainability.

A comprehensive systematic review: Impact of Land Use/ Land Cover (LULC) on Land Surface Temperatures (LST) and outdoor thermal comfort

Globally, urbanization-driven changes in Land Use and Land Cover (LULC) jeopardize Land Surface Temperatures (LSTs) and the outdoor thermal comfort of urban residents. While urban heat stress's impact on outdoor thermal comfort garners ample scholarly attention, research on the parallel influence of LULC remains limited. This paper comprehensively reviews prevalent tools for collecting LULC data, criteria for evaluating LST and outdoor thermal comfort, correlation measures and mitigation strategies. Focused on peer-reviewed publications from the last 25 years, our data is drawn from Scopus, Web of Science, Google Scholar and Science Direct.Our findings reveal Landsat and geographic information systems (GIS) as predominant datasets and processing platforms for LULC and LST information delineation. Common outdoor thermal comfort indices include the Universal Thermal Climate Index (UTCI), Physiologically Equivalent Temperature (PET) and Surface Urban Heat Island Intensity (SUHII). Validation employs Normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI) and Pearson's correlation. Geographically, Asia and Africa feature prominently in studies, with Europe comparatively underrepresented. We also highlight key LULC mitigation strategies, including augmenting vegetation in moderate climates, effective albedo management in warmer climates, and optimizing urban layouts for enhanced outdoor thermal comfort.

A Comparative Analysis of Outdoor Thermal Comfort Indicators Applied in China and Other Countries

Outdoor thermal comfort is an important criterion for evaluating the quality of outdoor activity environments and is also a significant indicator for assessing sustainable building design. Over the past century, more than 165 indoor and outdoor thermal comfort indexes have been developed to define human thermal comfort conditions under various circumstances and to quantify indoor and outdoor thermal environmental conditions. However, in the process of outdoor thermal comfort indicators becoming widely used worldwide, it remains a pressing research issue to compare the current state of application in China and other countries, identify the key areas of application for both sides, and outline the trends in outdoor thermal comfort index application. This study analyzed 346 articles on outdoor thermal comfort indicators. Employing bibliometric methods, we outline the general landscape of outdoor thermal comfort index applications in China and other countries. Additionally, we utilize comparative analysis to uncover similarities and differences in the research focus on outdoor thermal comfort. The research findings indicate the following: (1) Compared to China, other countries started outdoor thermal comfort index application research earlier. Their papers have higher average citation counts and engage in close academic collaborations. However, the quantity of published papers is fewer than in China. (2) The top five frequently used indexes in both China and other countries are PET (including mPET), UTCI, PMV, SET* (including OUT_SET*), and THI (including DI). China tends to use PET and UTCI more frequently than other countries. (3) The potential future directions for outdoor thermal comfort index applications in both China and other countries include: “monitoring and controlling regional outdoor thermal comfort at the temporal and spatial scales”, “multi-factors coupling effects on outdoor thermal comfort”, “human health assessment and prediction based on outdoor thermal comfort”, and “utilizing computational algorithms to calculate outdoor thermal comfort”. This study can serve as a reference for researchers and designers in the industry, contributing to the creation of sustainable outdoor environments.

On the identification and characterization of outdoor thermo-hygrometric stress events

Human thermal sensations are not controlled merely by the ambient temperature, but also by other biometeorological variables and personal factors. Therefore, thermo-hygrometric stress events need to be identified and monitored in addition to heat waves. The purpose of the present article is proposing a method for detection and characterization of thermo-hygrometric stress events, based on the rearrangement of heat waves indices and on new quantities. The Mediterranean Outdoor Thermal Comfort Index (MOCI) is used as a reference variable instead of the air temperature. The method is applied to Milan (Italy) for the 2022 summer, which: i) is the hottest in the period 1991–2020 with a temperature anomaly of 3.17 °C and ii) presents higher minimum temperatures (1.5 times higher) than those of the control period. The analysis of daytime values of MOCI demonstrates a cumulative MOCI higher than zero only in 2022. Hence, the lower fraction of data in the cold range determines a significant increase in the cumulative MOCI. The metrics on severe MOCI events in 2022 confirm the key-role of extreme temperatures. The proposed method is effective and, in this case, reveals the relevance of the cumulative thermal and thermo-hygrometric loads also in the absence of critical heating conditions.

The COMFA model for assessing courtyard thermal comfort in hot and humid regions: A comparative study with existing models

The present study introduces the development of the COMFAcourtyard model, which combines the strengths of COMFA, PET and SET* to create a reliable, practical and scientifically validated outdoor thermal comfort index for courtyards in hot and humid regions. To validate the model, four elements were implemented: validation in a real scenario (two classical courtyards in central Guangdong, China), comparison with relevant models (PET, SET*, UTCI, WBGT and COMFA), sensitivity analysis and statistical quantification of performance. Results show that COMFAcourtyard outperforms other models in terms of accuracy, interpretability and computational speed, with an R2 of 0.78 for linear regression and the ability to output intuitive and physically meaningful heat flow values. In terms of computational efficiency, COMFAcourtyard is approximately 1.5 times faster than COMFA and is two orders of magnitude faster than PET and SET*. In this study, a deeper understanding of the mechanisms of human thermal comfort is attained and the accuracy, interpretability and computational speed of the newly developed COMFAcourtyard model and previous models are systematically evaluated. The study also establishes a theoretical foundation for the thermal sensation scale and comfort thresholds in humid and hot courtyard environments. These efforts advance the design of climate-resilient outdoor environments and contribute to providing thermal security for individuals in the context of climate change.

Nature-Based Solutions for Cooling in High-Density Neighbourhoods in Shenzhen: A Case Study of Baishizhou

These days, high-density cities are facing growing challenges related to the urban heat island (UHI) effect. Greening can be a nature-based solution for UHI effect mitigation. This study aims to evaluate the potential of nature-based solutions to improve the urban living environments in Baishizhou, a high-density neighbourhood in Shenzhen. An integrated 3D visualisation research method was proposed in this study. Rhino 7, Grasshopper, and ENVI-met software were combined to evaluate environment characteristics before and after design, as well as compare differences in the outdoor thermal comfort index and the building surface temperature. The greening design scenarios include adding trees, green roofs, and green facades. The simulations ran for 24 h during the test period from 01:00 to 24:00 on 9 August 2019, which was the hottest day in Shenzhen. Baishizhou was selected as the test area for this study and environmental simulation. Results indicated that (1) vegetation has a positive cooling effect, providing outdoor thermal comfort, while shade “trees” provide significant cooling effects on hot days in tropical and subtropical climates; (2) adding green roofs and green facades to a building can significantly affect the cooling effect.

Influence of Microclimate on Older Peoples’ Outdoor Thermal Comfort and Health during Autumn in Two European Cities

Public spaces and green areas have been proven to influence people’s mental and physical health, thermal comfort being one of the main indicators. The growing trend of an ageing population globally led this research to analyse the outdoor thermal comfort of older adults in public spaces from two cities in Europe: Madrid in Spain and Newcastle upon Tyne in the United Kingdom during autumn. A mixed methodology through environmental measurements and surveys was performed in situ. In addition, the UTCI (Universal Thermal Climate Index) and PET (Physiological Equivalent Temperature) outdoor thermal comfort indices were applied. The results highlighted the risk of thermal stress and the vulnerability of this group of the population to the effects of climate on their health. Although most older people had ‘neutral’ thermal sensation, 86.3% of them would be at risk of cold stress in Newcastle, whilst in Madrid 31.5% would be at risk of cold stress and 35.7% of heat stress. Those results could be a starting point for the design of more comfortable and healthy public spaces that improve the quality of life of all citizens within the guidelines of active ageing and healthy cities.

Establishment of outdoor thermal comfort index groups for quantifying climate impact on construction accidents

The construction industry is significantly influenced by various outdoor weather factors, which affect the thermal comfort of workers and, subsequently their productivity and health. Existing studies regarding outdoor thermal comfort only consider the daytime or a specific season. However, this study considers all seasons and regions based on accident data and aims to analyze the relationship between construction accidents and the outdoor thermal comfort index based on the frequency and probabilities by using accident data from the construction industry. In addition, Physiological equivalent temperature groups based on their impact on accidents are developed to classify the accident probability by climate index level. This study is conducted in the following five steps: (i) collection of data, (ii) calculation of the outdoor thermal comfort, (iii) calculation of the relative frequency, and (iv) conducting statistical analyses. As a result of the relative probability analysis, which is the concept of probability, it was found that the probability of accidents was the highest at PET temperature of 34.7 °C and 2.95. That is, as the PET temperature decreases or increases, the relative frequency indicating the probability of an accident increases. In addition, seven outdoor thermal comfort index grades were classified based on relative frequency.

Linking landscape spatial heterogeneity to urban heat island and outdoor human thermal comfort in Tokyo: Application of the outdoor thermal comfort index

Rapid urbanization and high-density development are major drivers of global warming. The associations of spatial landscape patterns with urban thermal environments have been extensively investigated. Meanwhile, quantifying the cooling effects of landscape patterns on street-level outdoor thermal comfort has been less attempted. This study examined the relationship between the spatial heterogeneity of landscape patterns and urban residents’ outdoor thermal comfort in Tokyo, Japan. The cooling effects of the greenery pattern – configurations and compositions – on thermal comfort were explored while considering the interaction effects of greenery patterns with water bodies and urban densities. Our study findings indicated that spatial landscape patterns have a statistically significant impact on outdoor thermal comfort, showing 69% of explanatory power (Adj-r2) in the spatial error model. The cooling effects of greenery were improved when their spatial patterns were in a more aggregated, less fragmented, and less complex shape. Furthermore, outdoor thermal stress was relatively lower when there was simple shape greenery in low-density areas or complex shapes but in high-density areas while indicating synergies between them. Our findings would provide microclimatic urban planning and design implications of how to spatially configure urban greenery to improve outdoor thermal comfort.

A Preliminary Study of Summer Thermo-Hygrometric Comfort under Different Environmental Conditions in a Mediterranean City

The thermo-hygrometric sensation of pedestrians in outdoor environments can be quantified by means of bioclimatic indices. In this work, the Mediterranean Outdoor Thermal Comfort Index (MOCI) is applied in the city of Rome (Italy) for the purpose of investigating the effect of local environmental conditions (urban, suburban, rural) on pedestrian thermal comfort. Hourly values of MOCI are calculated for the May–September period in the years 2015–2021 using weather quantities acquired by the four monitoring stations of the Regional Agency for Environmental Protection included in the metropolitan area of Rome. MOCI data are analyzed based on the comfort and (cold/hot) discomfort conditions during both daytime and nighttime. At the urban station, 26% of daily records exceed the comfort threshold revealing the effect of urban overheating, whereas only 0.1% of hot discomfort occurrences are recorded overnight. Here, greater nighttime thermal comfort is experienced than in non-urban locations suggesting that the nocturnal thermo-hygrometric conditions are satisfactory for inhabitants in downtown Rome, despite the urban heat island. It also suggests that other factors, such as orography and atmospheric circulation, influence outdoor thermal comfort. The development of this work will therefore include at least these two elements.

The Metamatrix of Thermal Comfort: A compendious graphical methodology for appropriate selection of outdoor thermal comfort indices and thermo-physiological models for human-biometeorology research and urban planning

Ongoing climate crisis increase people's outdoor thermal stress, discouraging outside activities and intensifying indoor consumptions. Amelioration of urban microclimates is necessary to safeguard citizens from thermal strokes without energy-intensive strategies, ensuring future cities’ sustainable development. More than 200 calculation methods can be adopted with the purpose to design thermally comfortable public spaces, but existing literature lacks selection criteria to justifiably choose the appropriate ones. As resolution, the Metamatrix of Thermal Comfort has been developed. It's a graphical methodology, addressed to academicians and practitioners, that allows to rapidly comprehend and compare the specificities of 65 renowned thermal comfort indices and thermo-physiological models, explaining their mutual interactions. To promote practicality in thermal comfort studies, relying on calculation tools, an Operational version, including only 22 indices and models integrated in computer programs, is presented. A qualitative evaluation by approximately 30 criteria, such as climatic and physical factors, meteorological conditions, solar exposure and type of environment, allows to select thermal comfort calculation methods compatible to specific needs. To find appropriate computational tools, the Metamatrix of Software can be consulted. An application example is provided, proving the suitability of this graphical methodology as a powerful asset to apply outdoor thermal comfort-driven design to urban planning.

Urban Climate Risk Mitigation via Optimal Spatial Resource Allocation

Decision makers (DMs) who are involved in urban planning are often required to allocate finite resources (say, money) to improve outdoor thermal comfort (OTC) levels in a region (e.g., city, canton, country). In this paper, for the first time, we address the following two questions, which are directly related to this requirement: (1) How can the statistical properties of the spatial risk profile of an urban area from an OTC perspective be quantified, no matter which OTC index the DM chooses to use? (2) Given the risk profile, how much and where should the DM allocate the finite resources to improve the OTC levels? We answer these fundamental questions by developing a new and rigorous mathematical framework as well as a new class of models for spatial risk models. Our approach is based on methods from machine learning: first, a surrogate model of the OTC index that provides both accuracy and mathematical tractability is developed via regression analysis. Next, we incorporate the imperfect climate model and derive the statistical properties of the OTC index. We present the concept of spatio-temporal aggregate risk (STAR) measures and derive their statistical properties. Finally, building on our derivations, we develop a new algorithm for spatial resource allocation, which is useful for DMs and is based on modern portfolio theory. We implemented the tool and used it to illustrate its operation on a practical case of the large-scale area of Singapore using a WRF climate model.

Evaluating urban outdoor thermal comfort: a validation of ENVI-met simulation through field measurement

Thermal comfort plays a significant role in encouraging people to utilize outdoor spaces. Therefore, this feature must be analyzed and evaluated in order to be improvised. Computational fluid dynamics (CFD) is an alternative technique that predicts thermal comfort and environmental parameters. Validation of CFD is important to ensure its effectiveness. This study assessed the performance of ENVI-met for its ability to estimate thermal indices (PET) by comparing it to field measurement for various points in a street canyon in Port Said, Egypt, throughout the summer and winter seasons. Except for the limited air velocity correlation, the results presented very good agreement, particularly with respect to the final results of the PET visually curved and numerical values, with an index of agreement value ranging from 0.81 to 0.95. The study's conclusions concern the use of the ENVI-met simulation model as a tool for assessing outdoor thermal comfort. Highlights Outdoor thermal comfort was investigated in a hot-humid climate. The effectiveness of using a Computational fluid dynamics (CFD) simulation software program such as ENVI-met was evaluated as an alternative technique in urban design. Varied environmental parameters and outdoor thermal comfort indices were evaluated. It was concluded that validating CFD simulation through field measurement was significant in offering integrated decisions for urban design. Abbreviations: Environmental parameters; Ta; Air temperature; Tmrt; Mean radiant temperature; RH; Relative humidity; Va; Air velocity; Thermal comfort indices; PMV; Predicted mean vote; r; PPD; Predicted percentage of dissatisfaction; PET; Physiological Equivalent Temperature; UTCI; Universal Thermal Climate; UCB; University of California-Berkeley; ETU; universal effective temperature; Simulation Software; CFD; Computational fluid dynamics; UCB; University of California-Berkeley; LES; Large Eddy Simulation; RANS; Reynolds Averaged Navier Stoke; Error calculations; r; Pearson correlation coefficient; R2; Coefficient of determination; RMSE; Root Mean Squared Error; MAE; Mean Absolute Error; IA; Index of agreement; ASHRAE; American Society of Heating; Refrigeration; and Air-Conditioning Engineers.

Establishment of Outdoor Thermal Comfort Index Groups for Quantifying Climate Impact on Construction Accidents

Establishment of Outdoor Thermal Comfort Index Groups for Quantifying Climate Impact on Construction Accidents

Linking Landscape Spatial Heterogeneity to Urban Heart Island and Outdoor Human Thermal Comfort in Tokyo: Application of the Outdoor Thermal Comfort Index

Linking Landscape Spatial Heterogeneity to Urban Heart Island and Outdoor Human Thermal Comfort in Tokyo: Application of the Outdoor Thermal Comfort Index

Development and initial tests of an urban comfort monitoring system

The paper presents a newly developed low-cost measurement system for outdoor comfort monitoring. The solution is based on IoT (Internet of Things) technologies and is cloud-connected. The system is able to collect physical environment data, and includes a movable GPS monitoring station as well as the subjective thermal sensation of pedestrians via a devoted app. The cloud interface promptly elaborates the received data to calculate outdoor thermal comfort indices such as UTCI (Universal Thermal Climate Index), MRT (mean radiant temperature), and ET (effective temperature). The system is conceived for supporting both fixed and traveling measurements, and to support correlation studies between monitored environmental variables and personal comfort sensations to promote the local adaptation of comfort indices. Results from early testing are also reported.

Detailed thermal indicators analysis based on outdoor thermal comfort indices in construction sites in South China

Extreme thermal environment harms the health of outdoor workers and poses a potential threat to workplace safety. A field survey, including thermal parameter measurements, was conducted at construction sites in South China during the summer of 2019. The relationship between health risk and thermal parameters was obtained. The thermal sensation and satisfaction rate of the workers at different outdoor environmental conditions were analyzed, and recommendations were made based on the comparison of thermal indices. The thermal stress categories of the thermal indices were also investigated. The results suggest that the intensity of working conditions should be reduced when the air temperature is higher than 34 °C; the satisfaction rate of workers was found to be relatively high when the outdoor temperature is lower than 34 °C and the wind speed is greater than 1.3 m/s. Thermal indicators used to evaluate the comfort level of outdoor workers need to be modified according to the local climate and working environment to avoid excessive exposure to high-temperature work environments.

The Development of New Generation of Manikin for Outdoor Thermal Comfort Evaluation – A Literature Review

Urban Heat Island (UHI) is a challenge to human in the following decade as a result of continuous urbanization without appropriate planning and design. The impacts of UHI will getting worse due to the increase of population density with improper urban development especially in dense metropolitan cities. In the point of view of outdoor thermal comfort, a prolonged exposure to the outdoor heat will significantly contribute to human discomfort and health problems. Therefore, various research efforts have been implemented for developing solutions the mitigation strategies. The development of thermal manikin is one of mitigation effort to investigate the occurrence of UHI and to evaluate thermal comfort in microclimate conditions as representative of human simulation model. Hence, the aim of this paper is focused on the consideration that are required to develop a thermal manikin for outdoor thermal comfort assessment which include outdoor thermal comfort index, development of thermal manikin and material for thermal manikin for outdoor thermal comfort assessment.