Thermal Comfort Studies Research Articles

A novel outdoor thermal comfort simulation model for heritage environments (OTC-SM-HE): Verify the effectiveness in Gulangyu, China

The study of outdoor thermal comfort (OTC) for heritage environments can offer essential guidance for the articulation of multiple values of cultural heritage and the sustainable development of traditional settlements. However, previous study methods often fail to capture the complexity and diversity of heritage environments completely. This study proposes a novel outdoor thermal comfort simulation model for heritage environments (OTC-SM-HE) based on 3D real scene modeling technology and universal thermal climate index (UTCI). The effectiveness of the model is verified by comparing it with field test data in Gulangyu Island. The results show that: 1) UTCI are calculated by OTC-SM-HE and field testing showed high proximity started at 14:00 or 15:00 in the same space on different dates, respectively. 2) The mean error is 2.02 °C of UTCI in the same period and space, and the mean d-index of validation of models is 0.735.3) The similarity of trend duration is 85% in field test time. Thus, OTC-SM-HE can be shown to be effective in terms of response spatial characteristics, numerical values and variation trends. The establishment of OTC-SM-HE aims to simulate and evaluate the effects of meteorological conditions, shading facilities, and greening measures on the OTC of visitors and residents in different heritage environments. It provides a scientific basis and optimization recommendations for the sustainable management of heritage environments.

Outdoor Thermal Comfort Optimization in a Cold Climate to Mitigate the Level of Urban Heat Island in an Urban Area

Climatic and micro-climatic phenomena such as summer heat waves and Urban Heat Island (UHI) are increasingly endangering the city’s livability and safety. The importance of urban features on the UHI effect encourages us to consider the configuration of urban elements to improve cities’ sustainability and livability. Most solutions are viable when a city redevelops and new areas are built to focus on aspects such as optimum design and the orientation of building masses and streets, which affect thermal comfort. This research looks beyond outdoor thermal comfort studies using UHI data and geoprocessing techniques in Tallinn, Estonia. This study supposes that designing urban canyons with proper orientation helps to mitigate the UHI effect by maximizing outdoor thermal comfort at the pedestrian level during hot summer days. In addition, optimizing the orientation of buildings makes it possible to create shaded and cooler areas for pedestrians, reducing surface temperature, which may create more comfortable and sustainable urban environments with lower energy demands and reduced heat-related health risks. This research aims to generate valuable insights into how urban environments can be designed and configured to improve sustainability, livability, and outdoor thermal comfort for pedestrians. According to the study results, researchers can identify the most effective interventions to achieve these objectives by leveraging UHI data and geoprocessing techniques and using CFD simulations. This evaluation is beneficial in guiding urban planners and architects in proposing mitigation solutions to enhance thermal comfort in cities and creating suitable conditions for approved thermal comfort levels. Results of the study show that in the location used for the survey, Tallinn, Estonia, the orientation of West-East offers the optimum level of comfort regarding thermal comfort and surface temperature in the urban environment.

Occupancy and Thermal Preference-Based HVAC Control Strategy Using Multisensor Network

Human-in-the-loop Heating, Ventilation and Air Conditioning (HVAC) control-based methodologies have gained much attention due to continual discomfort compliance of occupants in residential and commercial buildings; spawning thermal comfort research interest in leveraging emerging advanced technologies to address the prolonged problem of discomfort and energy efficiency. In the past, thermal comfort studies have been conducted to determine the thermal sensation, preference and comfort based on the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Global Thermal Comfort Database II and customized dataset through machine learning. The ASHRAE Database II is an open-source database that includes sets of objective indoor climatic observations with corresponding subjective evaluations by the building occupants who were used as subjects in experiments. Environmental parameters and occupants’ skin temperature have been used to develop machine learning algorithms to predict thermal comfort indices in both indoor and outdoor settings. However, none of these studies have investigated merging environmental parameters and thermal images to predict thermal comfort indices of occupants. In this study, the holistic understanding of individuals thermal comfort environment was considered by fusing analog environmental sensors and thermal images captured at the time of the subjective measurement. Wavelet scattering features were obtained from the occupants’ thermal image surroundings and joined to the environmental parameters. This research developed different machine learning models, processing methods and evaluated the results based on the fused dataset. The results show the possibility of real time prediction of occupancy and thermal preference through classical machine learning, and stacked models with high accuracy. The proposed framework achieved an estimated 45% mean energy savings during a ten-day energy analysis.

The Ventilation Capacity of Earthen Vernacular Buildings With Timber Projections (Sachnisi) in Dense Urban Canyons – Findings From a Field Study in the Mediterranean

Vernacular architecture employs numerous elements for enhancing natural ventilation, especially in the Mediterranean climate. However, the cooling effectiveness of natural ventilation also relies on occupant behaviour and is highly determined by urban scale attributes. Still, airflow in real, inhomogeneous historic urban settings is rarely integrated in the thermal comfort studies of historic buildings. In this study, a multi-scale approach is adopted in order to assess the role of ventilation in establishing thermal comfort in earthen buildings, in real field conditions. This is achieved by addressing field monitoring of air velocity, temperature and relative humidity in: a) a dense (packing density λp=0.60) and inhomogeneous historic neighbourhood in Nicosia, Cyprus (measurement at a reference height); b) the street-canyon (measured at the mid-height of a narrow canyon with aspect ratio 2); and c) the interior of a typical adobe building with semi-open, pass-through spaces (portico) and closed timber projections with multiple openings, called sachnisi. Building ventilation was addressed as a function of in-street and rooftop airflow. Indoor thermal comfort was assessed in the case of specific ventilation patterns, comparing three adaptive comfort models. The results highlight the complexity of airflow in real inhomogeneous urban canopies and demonstrate that air velocity level in the street canyon is approximately one third of the reference free-stream wind velocity, while indoor air velocity remains at minimum levels. The study also reveals the contribution of night-time ventilation in cooling. Finally, spatial differentials of indoor environmental conditions in the portico were recorded for the first time, demonstrating the role of the sachnisi as a wind-capture element.

A Prospective Study of Thermal Comfort in Users in Technical Institution TVET: Workshop Facilities Space

Thermal comfort is a part of indoor environmental quality that should be considered to ensure the occupants' well-being. Unconducive buildings not only bring occupants discomfort but also tend to affect health, disrupt the process of teaching and learning, and reduce work productivity. Thus, this study determines the thermal condition of existing workshop buildings used in Technical and Vocational Education and Training (TVET) implementation. Evaluations of comfort are based on occupant surveys and environmental measurements. A total of 257 people completed a questionnaire distributed at three technical institutions in Kedah, Malaysia. According to the findings, the average thermal sensation vote is 1.85, which leads to 66.5% of respondents feeling discomfort. Meanwhile, the adaptive model analysis showed that the workshop environmental conditions were out of the comfort zone and did not comply with the ASHRAE 55 standard. Hence, the thermal discomfort factors from the occupants' perspective were identified and widely discussed. As a result, the research findings will benefit parties involved in new building construction or existing building renovations to improve indoor air quality.

A Review on the Impacts of Urban Heat Islands on Outdoor Thermal Comfort

The worsening urban heat island (UHI) effect poses a great challenge to the thermal comfort of people outdoors. However, there has not been a summary of the mechanisms by which UHI affects outdoor thermal comfort (OTC). This paper reviews the commonly used OTC evaluation indexes, data collection methods, and mitigation measures and discusses the relationship between UHI and OTC. The review is limited to peer-reviewed journal publications found in five databases: Science Direct, Scopus, Google Scholar, PubMed, and Web of Science. The review results indicate that physiological equivalent temperature (PET), universal thermal climate index (UTCI), and wet bulb globe temperature (WBGT) are the most widely used indexes in outdoor thermal comfort studies. The data collection methods mainly include questionnaire surveys, measurement, simulation, and formula calculation. There are four main approaches to mitigating the UHI effect in order to improve the comfort of people outdoors: vegetation strategies, water strategies, urban planning strategies, and material strategies. Future research can focus on developing OTC research methods and indexes and combine thermal comfort with visual comfort, auditory comfort, etc. to better evaluate the overall comfort.

Studi Kenyamanan Termal Siswa Sekolah Dasar Negeri (Studi Kasus: Sekolah Dasar Negeri 06 Sukabumi Selatan, Jakarta Selatan)

Thermal comfort studies have been carried out at Public Elementary School 06 Sukabumi Selatan, Jakarta, Indonesia. The schools that were observed were public schools that relied only on natural ventilation. Climatic parameters, namely air temperature and radiation temperature, relative humidity, and air speed were recorded together with the choice of seven scale subject comfort. The number of students in the state school was 82 people, consisting of 39 boys and 43 girls who were involved in this study. The study subjects were between 8 and 13 years old in public schools. The comfortable temperature of students at Public School 06 Sukabumi Selatan is 27.82°CTa higher than the current Indonesian comfort standard. This research examines the entire study and draws some conclusions from it

A machine learning led investigation to understand individual difference and the human-environment interactive effect on classroom thermal comfort

The availability of the global thermal open database means that machine learning models have been increasingly applied in thermal comfort studies in order to understand the factors and mechanisms that affect human thermal sensation. Previous global database analyses focused less on classroom thermal comfort, however, and more on model accuracy, while model interpretation was usually ignored, and individual differences and interaction effects are particularly poorly explained. This study screened 4527 related records about classrooms from the ASHRAE Global Thermal Comfort Database II, and used the cleaned data to train a hybrid model of extreme gradient boosting (XGBoost) and Bayesian optimisation (BO). SHAP values were used to interpret the machine learning model. The results identified ten key influencing factors that are associated with thermal comfort, although their importance varies among individuals. The effects of the factors can also be divided into main effects (80%) and interactive effects (20%), and some interactive effects are more potent than the main effect. Three typical types of interactive effects are concluded: two-way interaction, one-way interaction, and cross-interaction. This study was based on a comprehensive global database and an innovative machine learning method, and will lead to a more robust personal comfort model (PCM) that guides HVAC design and regulation development in order to meet thermal environment and energy-saving requirements.

The Effect of Commercial Building Orientations on Indoor Climate in Tropical Environments: A New Insight on Thermal Comfort Studies

The Effect of Commercial Building Orientations on Indoor Climate in Tropical Environments: A New Insight on Thermal Comfort Studies

Transient thermal comfort and physiological responses following a step change in activity status under summer indoor environments

People always experience changes in their daily activities. However, previous dynamic thermal comfort studies have focused on the changes in environmental parameters. Transient subjective and physiological responses following a step change in the activity status have rarely been addressed. To address this, 21 healthy male subjects dressed at 0.5 clo underwent three sessions: sitting for 15 min, walking for 20 min, and sitting for 20 min under three typical summer indoor conditions (operative temperatures (Top) and relative humidity: 23 °C and 60 %, 26 °C and 50 %, and 29 °C and 40 %). There were two walking speeds: 2 and 4 km/h. In addition to subjective votes, physiological parameters such as metabolic rate, skin temperature, and skin wettedness were investigated. The variations in the rate of heat loss from the skin, the rate of heat storage (S), and the core temperature were analysed using the JOS-3 model. The results showed that S was above zero while walking because of the delay in sweating. The heat storage took more than 20 min to dissipate at a typical summer indoor Top (23–29 °C) after experiencing moderate activity intensities (2.2–3.4 met). People were more sensitive to changes in core temperature during the downstep of activity than during the upstep of activity. The findings from this study revealed patterns of change in thermal comfort following a step change in activity status, which can be used to expand the theory of dynamic thermal comfort.

A Review of Different Methodologies to Study Occupant Comfort and Energy Consumption

The goal of this work is to give a full review of how machine learning (ML) is used in thermal comfort studies, highlight the most recent techniques and findings, and lay out a plan for future research. Most of the researchers focus on developing models related to thermal comfort prediction. However, only a few works look at the current state of adaptive thermal comfort studies and the ways in which it could save energy. This study showed that using ML control schemas to make buildings more comfortable in terms of temperature could cut energy by more than 27%. Finally, this paper identifies the remaining difficulties in using ML in thermal comfort investigations, including data collection, thermal comfort indices, sample size, feature selection, model selection, and real-world application.

A quick identification model for assessing human anxiety and thermal comfort based on physiological signals in a hot and humid working environment

We propose a simple and quick method for quantifying workers' anxiety and thermal comfort levels using physiological signals. Nine subjects enrolled in a series of controlled laboratory experiments involving varying temperature, relative humidity, and labor intensities. A total of 40 experiments were conducted, and 1592 groups of anxiety data and 1624 groups of thermal comfort data were obtained, respectively. During 2-h-working trials, Electroencephalogram (EEG), photoplethysmography (PPG), and pupil diameter of each subject were collected synchronously, and the State-Trait Anxiety Inventory (STAI) and thermal comfort vote (TCV) were completed in stages. Random Forest was adopted to screen out the appropriate sensitivity feature indicators of anxiety levels and thermal comfort levels from the 70 features of the 10 EEG channels. Finally, Random Forest, Gradient Boosting Decision Tree, K-nearest Neighbor Algorithm, and Support Vector Machine were used to determine relevant physiological data combinations and modeling algorithms. The Precision of the anxiety level and thermal comfort level quick identification model based on Random Forest Algorithm can reach 81.04% and 84.79%, respectively. This suggests that the proposed quick identification method for assessing workers' anxiety and thermal comfort levels holds promise. Physiological data need to be obtained by monitoring only PPG, pupil diameter, and 5 EEG channels. By processing these data, the workers' anxiety and thermal comfort level could be judged realistically to ensure their safety. It is suggested that PPG, pupil diameter, and EEG should be considered all together in the future study of anxiety and thermal comfort.

A Review on Adaptive Thermal Comfort of Office Building for Energy-Saving Building Design

The thermal environment quality of office buildings has an important role because thermal comfort is directly related to human productivity. Thermal comfort conditions are influenced by climate, location, and the built environment; hence, comfort standards are required to assist building designers in creating a comfortable indoor environment for building occupants. In this context, the present study analyzes the adaptive thermal comfort studies conducted in office buildings from various countries. A large number of research articles selected from the Scopus database were considered for this study. Based on the analysis, outdoor climatic conditions have a greater influence on indoor thermal conditions in naturally ventilated than in air-conditioned office buildings. The temperature required for comfort is as low as 17.6 °C and as high as 31.2 °C in naturally ventilated buildings. An adaptive comfort equation for naturally ventilated and air-conditioned office buildings has also been proposed to predict the indoor comfort temperature. Various studies show that a substantial amount of energy can be saved by changing the set point and natural ventilation. Furthermore, this study successfully provides hearty evidence that there is a need for climate-specific standards on thermal comfort for energy-efficient design development because existing comfort standards might not be applicable to all climates.

A Review Paper on Thermal Comfort and Ventilation Systems in Educational Buildings: Nano-Mechanical and Mathematical Aspects

Thermal comfort has always been an essential factor that affects students’ productivity and success. Students spend considerable time at their schools or universities more than any other building type except their homes. Thus, indicating the importance of providing thermal comfort in educational buildings. Many studies worldwide are conducted to assess and optimize thermal comfort inside classrooms. However, the results have not been accurate even for similar study conditions due to the differences in the studies’ conditions. This paper focuses on thermal comfort studies in educational buildings (classrooms). The studies are divided into two sections, the first covering field studies methodologies, objective, and subjective questionnaires, and the second reviewing thermal comfort results based on the climatic zone, educational level, and analysis approach. It is recommended that thermal comfort studies be carried out using rational and adaptive models as they provide more accurate, reliable results. Also, it is found that thermal comfort standards are generally inadequate to assess thermal comfort in classrooms. Thus, other international standards should be created and considered for classroom assessment. Over the past few years, the combination between nanotechnology and architecture engineering has been widely used in several disciplines because of its crucial significance in finding new nanodevices to contribute in reducing of energy consumption, particularly on construction materials. Filling functionalized tools with nanoparticles plays a critical role in improving the thermal and optical properties, particularly with respect to nanofluids applications, i.e., buildings applications of thermal comfort. The experimental results of long-term studies show that the calculation values of optimization have a consistent agreement with the experimental transmission of nanofluids models.

Effect of Office Design Characteristics and Anthropometrics on Thermal Comfort in Malaysian Universities Air-Conditioned Buildings

Apart from indoor environmental and personal factors, contextual factors have significantly influenced several thermal comfort studies. In air-conditioned spaces, thermal comfort is conveniently attainable by adjusting the temperature settings, but indoor design elements might alter thermal perceptions and provide adaptive opportunities. This study examines the influence of office design characteristics and anthropometrics on thermal comfort parameters and perceptions. Nineteen university offices in Kuala Lumpur and Shah Alam, comprised of twelve shared and seven private spaces, were investigated, and 628 responses were collected from 42 participants with even gender distributions. The results showed that room occupancy and size were statistically significant with Griffiths’ comfort temperature. Offices with five or more people had lower mean comfort temperature (24.1 ℃) than private offices (25.0 ℃). The mean comfort temperature in offices larger than 80 m2 was 23.7 ℃ with warmer thermal preference, while offices smaller than 40 m2 were approximately one-degree Celsius higher. Offices with no shading device, window blinds opened, and tiled floorings had mean comfort temperatures higher than 25.0 ℃. The findings also indicated that offices with more than a 60% glazing ratio have a slightly higher mean comfort temperature at 24.9 ℃. The thermal sensation during closed blinds was much cooler than opened ones. The anthropometry of the human body impacts how heat is regulated; thus, respondents with higher Body Mass Index (BMI) and above-average body surface area (higher than 1.7 m2) had significantly lower comfort temperatures and preferred more humid surroundings. Mean comfort temperature was statistically significant with BMI with a noticeable difference between underweight (25.1 ℃), normal (24.5 ℃), and obese (23.9 ℃) BMIs. In this study, it is recommended that BMI be considered when positioning occupants in shared offices, and window blinds are an integral shading device for adjusting indoor thermal comfort levels.

Parametric study of design parameters and thermal comfort in primary schools in Ho Chi Minh City, Vietnam

Overheating of premises is a typical thermal discomfort issue in naturally ventilated primary schools in Ho Chi Minh City, Vietnam. Several design parameters were shown to affect the indoor thermal environment. A parametric study was conducted and based on several building performance simulations to investigate the influences of the individual design parameters on indoor air temperatures and the prevalence of overheating in primary schools. The sensitivity analysis indicated that the material of building envelopes, the openings, and the solar controls, in descending order, affected overheating occurrence. The findings could assist the architect in choosing which parameters should be prioritised in the design stage, which is particularly useful in renovation and retrofit projects.

Emergency conversion of sports halls into temporary hospitals caused by COVID-19 pandemic: Case studies of thermal comfort and energy consumption analysis

An emergency caused by the COVID-19 pandemic affected the rethinking of existing healthcare systems. The increased need for hospital beds appeared short after the outbreak of the pandemic and the solution was to adapt the existing buildings, primarily public ones. Among all, sports buildings, i.e. sports halls were successfully used around the globe for conversion into hospitals. Topic of the paper was to investigate whether sports halls in Serbia, which were also used as temporary hospitals, are suitable for conversion in terms of energy consumption needed for achieving thermal comfort. Two case studies were analysed. The energy simulations were done using the DesingBuilder software. The results of thermal comfort summary and energy consumption led to the conclusion that this building type in Serbia could be successfully used for hospital purposes. Although the multiple increase in energy consumption was noted during the heating period, the results were within the limits required by both national and international standards.

Basic methods used for data analysis in adaptive thermal comfort studies

Existing research literature on adaptive thermal comfort studies shows the methodology used and results obtained; however, the information for data analysis is reduced. Methods commonly used to interpret and understand the thermal comfort phenomenon are univariate type and, usually, use the linear regression to predict the behavior of one variable from the variation of other; among others, Simple Linear Regression method and Averages by Thermal Sensation Interval method can be identified, although it is also possible to find studies based on the ANSI/ASHRAE 55 method or on machine-learning algorithms. This document describes a procedure that allows three-stages data to be statistically processed: Database capture, Database preparation, and Data Correlation. In each case, the steps to be followed are specified and different statistical alternatives are indicated to achieve certainty in the results. From different studies specialized in thermal comfort, it is possible to identify that the Averages by Thermal Sensation Interval method offers results with greater consistency and causality regarding the perceived thermal sensation and its phenomenological correspondence with the monitoring of the environmental conditions. As a complementary resource, a personalized spreadsheet whit the three methods described in this paper is including.

An Investigation of Thermal Comfort in Classrooms in the Tropical Savanna Climate

Studying the thermal environment in classrooms is essential due to its impact on students' health, teaching, learning, and productivity. In the Nigerian context, there is a general lack of thermal comfort studies, and none specifically relate to secondary school settings. This study aims to investigate students' perceptions of the indoor thermal environment and to determine the optimum temperature in naturally ventilated classrooms in the tropical savanna climate. Field investigations were conducted in free-running classrooms in Abuja to evaluate occupants' thermal comfort and perceptions. The study involves 901 pupils from 21 classrooms. Data were obtained through physical measurements of thermal comfort variables and a questionnaire survey on occupants' perceptions of the indoor thermal environment. The objective assessment indicated that 86% of the classrooms were inconsistent with the ASHRAE standard–55. Although 60% of the pupils were satisfied with their thermal environment, 78% preferred a cooler than neutral temperature. The result revealed a comfort temperature of 28.9 oC. The results extend the literature on thermal comfort in classrooms to the tropical savannah climate of the west African sub-region, which has received little attention in earlier research. The findings provide foundation data for developing a comfort standard for classrooms in the zone.

Thermal Comfort Study of Outdoor Space for Face-to-Face Learning System

The transmission covid-19 virus is through droplets are splashed by people who have the virus. Therefore, activities that make crowding especially in closed rooms with poor air circulation are very avoided, because the rate of transmission in the inner room with poor air circulation has a higher presentation compared to transmission in the outside room. With new protocol to use maximum room capacity limit of 50%, using outdoor space can be good alternative solution to increase space for face to face learning system. But there is needed a study of thermal comfort for outdoor space. The object taken as a sample in this study was sitting area of the Undip Architect campus. This paper present measurements of dry temperature, humidity, and air movement with quntitative method. From the examine of effective temperture show that the object research have cozy thermal comfort according by Mom dan Wiesebron standards. This examamination of effective temperature can also be exam for other outdoor environments.