Comfort Research Research Articles

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

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

Review of studies on thermal comfort in Indian residential buildings

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

Globe thermometer free convection error potentials

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

Human behaviour should be recorded in (dis)comfort research

(Dis)comfort research that has no information on behaviour of the participants can be considered as incomplete, as major influencing factors could be missed. For (dis)comfort research it is important to capture factors such as context, task/activity, posture, movement, (distracting) stimuli and time, as these factors have influence on the experienced (dis)comfort. Recording the behaviour allows for better evaluation of and comparison between studies, contributing to an increase of scientific knowledge on (dis)comfort.

Indoor air quality and passenger thermal comfort in Beijing metro transfer stations

In this study, particulate matter was investigated as the primary pollutant in the air quality of Beijing Metro transfer stations, and passenger thermal comfort during the transfer process was evaluated by using the relative warmth index (RWI). Passenger thermal comfort level is not ideal in 87% of the measured space and is slightly hot overall, with an RWI range of 0.20–0.43. Although 20% of the measured space has lower values than ASHRAE’s cooling comfort class, the thermal comfort level of most measured space is good in winter morning rush hours, with an RWI range from −0.18 to 0.28. The particulate matter (PM) concentration is related not only to the season and spatial depth but also to the transfer design of the metro station. During the morning rush period, the concentration ranges difference of PM10 and PM2.5 in winter are 262.9 μg/m3 and 125.5 μg/m3, respectively, which are 1.43 and 1.46 times higher than those of in summer. There are significant differences in the PM concentration and RWI values between the island and lateral platforms of Beijing Metro transfer stations, and the design of the lateral platform is superior to that of the island platform. Another exploratory experiment is conducted to determine if the PM concentration has a potential effect on human metabolic rate. The data in this paper provide a valuable reference for further comfort research and environmental control in metro station, and the conclusions may guide the further underground space design of metro transfer stations.

Evaluating the Influence of Individualized Nursing Care on Chinese Postpartum Women

Objective: To evaluate the influence of individualized nursing care on Chinese postpartum women. Methods: We invited 182 participants to join our study, who are childbirth in the First Affiliated Hospital of Jinan University, their childbirth time is from April 2016 to October 2019. They were randomly assigned to control group (n=91) and intervention group (n=91), the two group receive different nursing services, such as individualized nursing care and traditional nursing services. We use Self-Rating Anxiety Scale (SAS), Self-rating depression scale (SDS) and other questionnaires to collect the data from participants, the data include patient comfort status, patient satisfaction status, anxiety status and depression status. Result: In comfort research, the comfort status of most patient is 0 level in control group and intervention group (n=44 & n=56). On the other hand, the control group had more 1 level assessment in this result (n=22). In satisfaction report, the performance of individualized nursing care is better than traditional nursing services in satisfaction [86 (94.5%) vs 77 (84.6%)]. In SDS and SAS research, The intervention group had greater improvement than that of control group in the SAS as the result of intervention group lowered scores even more. Conclusion: the individualized nursing care have great improvement to improve hospital satisfaction and mental health of patients. But the individualized nursing care has little effect on improving patient comfort.

Bayesian updates for indoor thermal comfort models

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

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

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

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

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

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

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

Effect of inhabitant behavioral responses on adaptive thermal comfort under hot summer and cold winter climate in China

The hot summer and cold winter zone is an important area in China, accommodated with huge population and occupying a great amount of the lands. Due to the local climate and long-term economic conditions, the adaptive thermal sensation of local residents and the thermal regulation behaviors have unique characteristics. The thermal regulation behaviors involve complicated dynamic features and many influencing factors. However, due to the limited experimental testing conditions, it is greatly lack of relevant studies on the characteristics of different thermal regulation behaviors and their influences on both indoor thermal environment and the thermal comfort in this zone. Aiming at this, taking the residential buildings in Hangzhou city as the main object, a large-scale questionnaire surveys and measurements were conducted. The characteristics of various types of thermal regulation behaviors and the annual indoor thermal environment are analyzed. The effects of each regulation behavior on the indoor thermal environment and the adaptive thermal comfort are revealed. Rectified adaptive coefficients for the actual situation of Hangzhou residents are proposed and it is proved that the modified values can be used to evaluate the adaptive thermal sensation of the local residents more precise than the original ones used in the National Standard GB/T 50,785–2012. Incorporating the modified adaptive coefficient λ into the APMV model, the potential impact of summer ventilation on thermal comfort is quantified. The research results can provide theoretical support for the energy saving-oriented indoor thermal comfort research in the region.

A Parametric Method for Remapping and Calibrating Fisheye Images for Glare Analysis

High Dynamic Range (HDR) imaging using a fisheye lens has provided new opportunities to evaluate the luminous environment in visual comfort research. For glare analysis, strict calibration is necessary to extract accurate luminous maps to achieve reliable glare results. Most studies have focused on correcting the vignetting effect in HDR imaging during post-calibration. However, the lens projection also contributes to luminous map errors because of its inherent distortion. To date, there is no simple method to correct this distortion phenomenon for glare analysis. This paper presents a parametric-based methodology to correct the projection distortion from fisheye lenses for the specific use in glare analysis. HDR images were captured to examine two devices: a 190° equisolid SIGMA 8 mm F3.5 EX DG fisheye lens mounted on a Canon 5D camera, and a 195° fisheye commercial lens with an unknown projection, mounted on the rear camera of a Samsung Galaxy S7. A mathematical and geometrical model was developed to remap each pixel to correct the projection distortion using Grasshopper and MATLAB. The parametric-based method was validated using Radiance and MATLAB through checking the accuracy of pixel remapping and measuring color distortion with Structural Similarity Index (SSIM). Glare scores were used to compare the results between both devices, which validates the use of mobile phones in photometric research. The results showed that this method can be used to correct HDR images projection distortion for more accurate evaluation of the luminous environment in glare research.

Reliability of an Item Set Assessing Indoor Climate in Offices—Results From Field Studies and Laboratory Research

Assessing building user needs and preferences is widespread and often questionnaire surveys are applied in order to assess environmental perception and satisfaction. A central question in this context is the quality of the questionnaires used, but little is known regarding their reliability. The present study addresses interdisciplinary aspects such as engineering and psychological sciences to answer the questions: Are the same item sets applicable in various settings (e.g., seasons)? Is there any difference in the reliability of item sets assessing user satisfaction in field vs. laboratory research? In the present study, reliability analyses of an item set regarding satisfaction with indoor climate including the ASHRAE thermal sensation scale (single-item) as well as the thermal preference question were conducted with respect to season, office type, age group, and sex. Field data were gathered via post occupancy evaluation from 46 office buildings in Germany. Additionally, comparable items from laboratory research were subjected to a reliability analysis. Results revealed predominantly good to excellent Cronbach's alpha values for the field studies. The values from the laboratory study were lower, although comparable (acceptable), partly due to the differences in variation in responses in field vs. laboratory settings. Results showed that questionnaires assessing user's satisfaction need to be set in relation with the given context for reliable interpretation. Further research could validate our results with larger samples for laboratory data. Interdisciplinary research is necessary in order to further develop methodological approaches in the field of user comfort research.

Factor of building orientation direction as determinant the thermal comfort quality

Generally determines the comfort quality of rooms in the building is due to the air temperature caused by solar radiation, humidity and air movement inside the building. A comfortable room influenced by the volume of space, wide opening in the wall, use of materials, patterns of shadows and vegetation around the building. But the specific factors that can impact directly on the quality level of comfort rooms in the building that is the building position with a different orientation direction. Standard guidelines thermal comfort for the humid tropics to be achieved is at the limit of 24°C < T <26°C. Thermal comfort research was conducted in a pilot house in the Faculty of Engineering, Christian University of Indonesia (FT-UKI), Cawang, East Jakarta. The thermal comfort research lasts for 2 (two) months. Indoor air temperature in the pilot house of FT-UKI does not meet the requirements of thermal comfort standard for each building orientation direction during the research. But on average, building orientation direction were relatively convenience in this research is northwest - southeast, it also minimizes design of engineering and construction to the surrounding environment.

Thermal sensitivity of occupants in different building typologies: The Griffiths Constant is a Variable

The Griffiths method is widely used in thermal comfort studies to derive building users’ comfort temperature, or thermal neutrality as it is sometimes known. A single value (so called the Griffiths Constant, typically 0.5/°C) is prescribed as a representation of thermal sensitivity of building occupants to indoor temperature variations, which in turn is used to estimate indoor thermal neutrality from a subject's actual thermal sensation vote at a measured room temperature. Despite the Griffiths Constant of 0.5/°C having been used widely across the thermal comfort research literature and in some generic standards, the constant was derived exclusively from office building data and its applicability across different typologies is yet to be rigorously validated. The objective of this study is to quantify how sensitive people are to temperature variations inside a building, and to investigate if thermal sensitivity differs between different contexts (including building typologies, modes of ventilation, outdoor climatic types, and genders). A collection of thermal comfort field studies in different building typologies containing around 11,500 datasets was used to statistically derive building users’ thermal sensitivity, i.e. the rate of change in thermal sensation per unit change in indoor temperature within a day. Our results suggest that occupant thermal sensitivity does vary depending on building typologies and building ventilation mode. In naturally ventilated spaces users are about half as sensitive to temperature variations as in air-conditioned spaces. Age, gender and climate are found to be factors that can also influence thermal sensitivity of building occupants. Our findings imply that reliance on a universal thermal sensitivity value, the Griffiths Constant, in comfort temperature (neutrality) calculations should be avoided because it is in fact a variable.

Effect of seasonal adaptation on outdoor thermal comfort in a hot-summer and cold-winter city

ABSTRACTIn China, little research on outdoor thermal comfort has been conducted in the hot-summer and cold-winter zone where occupants are in the state of thermal discomfort for most time of the year. This paper presents results from both field measurement and questionnaire survey in the city of Wuhan in both summer and winter seasons about seasonal adaptation effect on outdoor thermal comfort. A total of 417 samples were collected in summer and 426 samples were collected in winter. The neutral standard effective temperature (SET*) in winter and summer was found to be 24.7°C and 25.6°C, respectively. Occupants achieved thermal comfort when their thermal sensation was slightly cool in summer and slightly warm in winter. The SET* with 100% thermal acceptance rate in summer and winter was found to be 27.9°C, 23.4°C, respectively. The results reveal large seasonal differences in achieving outdoor thermal comfort for people in hot-summer and cold-winter climate zone. This research can add more database to outdoor thermal comfort research in China and provide more insights into the thermal adaptation of seasonal effect on outdoor thermal comfort. Its findings can also assist urban designers to create thermally comfortable urban spaces in different seasons.

Preferred vs neutral temperatures and their implications on thermal comfort and energy use: Workplaces in Japan, Norway and the UK

This study recommends the application of “preferred temperature” rather than neutral temperature in thermal comfort studies, particularly when focused on finding the range of comfort temperatures. Currently, neutral temperature is considered as comfort temperature of the occupants in thermal comfort research. This study challenged this view and questioned the use of neutral temperature in thermal comfort studies, standard comfort zone and thermal comfort standards. Field test studies of thermal comfort were carried out on about 5,000 respondents in three distinct workplace contexts: Japan, Norway and the UK. Thermal sensation, preference and environmental measurements were collected and analysed using the Griffiths method. Preferred and neutral temperatures were compared in these three contexts and differences were observed. Overall, this study suggests that thermal preference (TP) is more likely to be a more accurate measure in assessing thermal comfort and particularly the direct implication of it in the real world context (e.g. changing the room temperature) is more likely to result in occupant comfort. It suggests that a neutral thermal sensation does not guarantee thermal comfort of the occupant, as the occupant may want other sensations than neutral (e.g. the occupant still prefers a change although feeling neutral). It is essential to recognise that non-neutral thermal sensations are considered as thermal comfort for some occupants and to include this in future research as well as the direct implication in setting the room temperature and the energy performance of the building.

An optimal control strategy for built environment based on the human thermal sensation

The automatic control strategy of existing heating, ventilation, and air-conditioning (HVAC) systems generally determine the set-point of building thermal environment in accordance with the relevant design criterion or occupants’ preference, and have not taken the real-time thermal sensation of human body into consideration, which may make the human body feel uncomfortable under the range of comfortable design parameters. In order to improve the thermal comfort of human body, this paper presented an optimal strategy for indoor building environment control based on the human thermal sensation. The control logic of indoor air temperature based on the thermal sensation of human body was given, and the linear adjustment algorithm was used for realizing the optimal adjustment of indoor temperature set-point. In order to evaluate the performance of the proposed control strategy, a numerical simulation platform was constructed, and a series of simulations were carried out to compare the set-point based and proposed control strategies. The results revealed that the proposed control strategy can improve human thermal comfort and have the potential in energy saving compared to the set-point based control strategy. The proposed control strategy is of significance for the application of current thermal comfort research results and the development of built environment automatic control theory.

Research of the Influence of Road Excitation on Human Body Comfort under the Harvester Working Condition

Abstract. When the harvester travels in the field, road excitation will cause low-frequency vibration within 3 Hz, which is the most sensitive frequency range of human body. In order to evaluate the influence of road excitation on the comfort feelings of the harvester driver, vibration acceleration data were collected when the combine harvester was travelling at high and low speeds on flat-soft road, flat-solid road, and rough-solid road. The vibration comfort of the harvester was evaluated by root mean square (RMS) of weighted acceleration. The results showed that the speed of harvester, road surface roughness and hardness have great effects on harvester vibration comfort. Soft road has an obvious absorption effect on the vibration at 70 Hz. The increase in the speed of harvester and road surface hardness and roughness elevates the subjective discomfort of the driver. Keywords: Combine harvester, Comfort research, Road excitation, Root mean square of weighted acceleration, Vibration test.

Outdoor thermal comfort research in urban areas of Central and Southeast Europe: A review

Constant urban population growth and intensive urbanization lead to increased pressure on urban areas leading to uncomfortable living conditions. The quality of urban living conditions often depends on the thermal comfort of the open urban spaces, which are used on the daily basis. That is the reason why the attention towards outdoor thermal comfort (OTC) is increasing in the last decade among the researchers from different fields of expertise. In this article, the review of the outdoor thermal comfort research in urban areas of 11 countries of Central and Southeast Europe in the last decade (2010-2019). The main aim of the review is to give a comprehensive, systematic and complete insight in the current situation in the OTC research interest. The results of the review show increased but uneven interest in outdoor thermal comfort by the end of the research period in countries of the Central and Southeast Europe. In total, 120 articles on the topic of outdoor thermal comfort were identified in the research area. The most significant contribution to the urban outdoor thermal comfort research comes from Hungary, Serbia and Greece. Furthermore, five research objectives were identified: methodology improvement and development, climate sensitive and comfortable urban design and planning, citizens/pedestrian comfort and health assessment and improvement, tourism and health sector support and literature review.