Impact of building regulations on the perceived outdoor thermal comfort in the mixed-use neighbourhood of Chennai

The population in urban areas is increasing rapidly around the world in most of the cities. In India, this growth has forced the local governments to review the planning norms regularly with the main focus of making an affordable urban living. This resulted in increasing the built density without evaluating the effect of such developments on human thermal comfort. Outdoor microclimate is one of the significant factors that determine the quality of outdoor spaces. This study investigates the potential impact of the built geometry guided by the newly published development control rules of Chennai, India on the various parameters that influence microclimate. The existing and future scenario has been modelled for three locations in a typical mixed-use neighborhood of Chennai. Further, air temperature and relative humidity were measured in three locations on a typical summer month of May 2018. The recorded data was used for validating the simulated model and calibrating the model settings. Most of the studies on outdoor thermal comfort compare a base case scenario and project future scenarios. This paper is a more realistic comparison of outdoor thermal comfort between the actual resultant built environment guided by the new Tamil Nadu Combined Development and Building Rules, 2019 for selected locations and the existing built geometry which is the outcome of revised development control rules of 2013. The study found a significant reduction of 18 C in mean radiant temperature (Tmrt) and a reduction of 12 C in Physiological Equivalent Temperature (PET) between the 2013 and the predicted built geometry as per 2019 building rules. Further the duration of extreme heat stress in the Physiological Equivalent Temperature (PET) scale show a reduction of 3 h during the day time. The study will assist urban planners and designers to include outdoor thermal comfort also as an important factor while developing building rules.     

Evaluation of coupled outdoor and indoor thermal comfort environment and anthropogenic heat

With rapid urbanization, big cities in the south of China are progressively falling short of sustaining outdoor thermal comfort. In this paper, a thermal comfort and energy evaluation model is derived from revisions of previous study, to simulate and predict the interaction of coupled urban building-site climate and then the thermal comfort. The methodology of principal calculations is demonstrated first, then a hypothetical district of office buildings in Shanghai is selected. Dynamic on-site climate parameters, anthropogenic heat and indoor/outdoor SET* values, etc., are simulated and evaluated. The results show the variation of outdoor SET* values influenced by factors including canopy height, building coverage and air-conditioning set-point temperature.     

Seasonal effects of urban street shading on long-term outdoor thermal comfort

As shading, an important factor in urban environments, affects thermal environments and long-term thermal comfort, this study conducted several field experiments to analyze the outdoor thermal conditions on urban streets in central Taiwan. The RayMan model was utilized for predicting long-term thermal comfort using meteorological data for a 10-year period. Analytical results indicate that slightly shaded areas typically have highly frequent hot conditions during summer, particularly at noon. However, highly shaded locations generally have a low physiologically equivalent temperature (PET) during winter. Correlation analysis reveals that thermal comfort is best when a location is shaded during spring, summer, and autumn. During winter, low-shade conditions may contribute to the increase in solar radiation; thus, thermal comfort is improved when a location has little shade in winter. We suggest that a certain shading level is best for urban streets, and trees or shade devices should be used to improve the original thermal environment.     

Outdoor thermal comfort and outdoor activities: A review of research in the past decade

Outdoor spaces are important to sustainable cities because they accommodate pedestrian traffic and outdoor activities, and contribute greatly to urban livability and vitality. In the global context of climate change, outdoor spaces that provide a pleasurable thermal comfort experience for pedestrians effectively improve the quality of urban living. The influence of thermal comfort on outdoor activities is a complex issue comprising both climatic and behavioral aspects; however, current investigations lack a general framework for assessment. This paper presents a review of research over the past decade on the behavioral aspects of outdoor thermal comfort. The article focuses on perceptions of outdoor thermal comfort and the use of outdoor space in the context of urban planning. We further discuss a general framework for assessing outdoor thermal comfort based on behavioral aspects and the need for predicting tools in the design and planning of outdoor thermal comfort.     

Shading effect on long-term outdoor thermal comfort

Shading affects outdoor thermal environments and, therefore, influences the thermal perceptions of people in outdoor spaces. Since most field studies examining outdoor thermal comfort merely elucidated characteristics measured on a particular day, these studies may not represent annual thermal conditions accurately. Therefore, this study conducted 12 field experiments to analyze outdoor thermal conditions on a university campus in central Taiwan, and utilized RayMan model for predicting long-term thermal comfort applying meteorological data for a 10-year period. The physiologically equivalent temperature (PET) is employed as a thermal index. The thermal comfort range of Taiwanese residents obtained in a previous survey was applied as the criterion for determining whether a thermal environment is comfortable or uncomfortable. Analytical results indicate that the sky view factor (SVF), which represents the percentage of free sky at specific locations, significantly affects outdoor thermal environments. Analytical results indicate that a high SVF (barely shaded) causes discomfort in summer and a low SVF (highly shaded) causes discomfort in winter. As Taiwan has hot summers and mild winters, sufficient shading should be provided by trees and buildings to improve thermal comfort in summer. However, since the Taiwanese have poor tolerance of cold temperature, outdoor space planning should avoid creating areas with excessive shading. Therefore, the thermal requirements of residents and characteristics of the local climate and environment must be considered when creating shaded outdoor areas.     

Thermal comfort in outdoor urban spaces: Analysis across different European countries

This paper presents some of the findings of the European project, RUROS, primarily concerned with the environmental and comfort conditions of open spaces in cities. The results of the microclimatic and human monitoring, in relation to the thermal environment and comfort conditions in open spaces, are presented. The database consists of nearly 10,000 questionnaire guided interviews from field surveys in 14 different case study sites, across five different countries in Europe. The findings confirm a strong relationship between microclimatic and comfort conditions, with air temperature and solar radiation being important determinants of comfort, although one parameter alone is not sufficient for the assessment of thermal comfort conditions. Overall comfort levels are over 75% for all cities on a yearly basis. There is also strong evidence for adaptation taking place, both physically, with the seasonal variation in clothing and changes to the metabolic rate, as well as psychologically. Recent experience and expectations play a major role and are responsible for a variation over 10 °C of neutral temperatures, largely following the profile of the respective climatic temperatures on a seasonal basis, across Europe. In this context, perceived choice over a source of discomfort is another important parameter for people in open spaces.     

Data generative machine learning model for the assessment of outdoor thermal and wind comfort in a northern urban environment

Predicting comfort levels in cities is challenging due to the many metric assessment. To overcome these challenges, much research is being done in the computing community to develop methods capable of generating outdoor comfort data. Machine Learning (ML) provides many opportunities to discover patterns in large datasets such as urban data. This paper proposes a data-driven approach to build a predictive and data-generative model to assess outdoor thermal comfort. The model benefits from the results of a study, which analyses Computational Fluid Dynamics (CFD) urban simulation to determine the thermal and wind comfort in Tallinn, Estonia. The ML model was built based on classification, and it uses an opaque ML model. The results were evaluated by applying different metrics and show us that the approach allows the implementation of a data-generative ML model to generate reliable data on outdoor comfort that can be used by urban stakeholders, planners, and researchers.     

Building envelope regulations on thermal comfort in glass facade buildings and energy-saving potential for PMV-based comfort control

This paper presents an investigation of the effect of building envelope regulation on thermal comfort and on the energy-saving potential for PMV-based comfort control in glass facade buildings. Occurrences and severity of overheating, based on the PMV-PPD model contained in ISO 7730, were used for the thermal comfort assessment. Parametric study simulations for an actual building with a large glass facade were carried out to predict the changes in thermal comfort levels in a space due to different glazing types, depths of overhang and glazing areas, which are the key parameters of the building envelope regulation index, named ENVLOAD, in Taiwan. The result demonstrates that the ENVLOAD has significant effect on thermal comfort. Additionally, comparative simulations between PMV-based comfort control and conventional thermostatic control were performed to investigate the changes in the energy-saving potential of a thermal comfort-controlled space due to changes of its ENVLOAD. The results demonstrate that the energy-saving potential in a PMV-based controlled space increases with low ENVLOAD conditions.     

A simple technique to classify urban locations with respect to human thermal comfort: Proposing the HXG scale

An attempt is made to present a new scale to study urban microclimates and outdoor thermal comfort using simple in-situ measurement data. For this purpose, six urban locations with distinct physical characteristics are selected in a metropolitan city, Chennai. At each location, three streets with diverse orientations (North–south; East–west and Northeast–southwest) are identified and their microclimatic conditions are monitored during the summer months of April, May and June. The variations in microclimate are studied using ANOVA single factor test and later, correlated with the site’s physical characteristics. The assessment of microclimate and outdoor thermal comfort is done using Physiological equivalent temperature (PET).     

Effects of thermal activated building systems in schools on thermal comfort in winter

There is a growing attention for the Indoor Air Quality problems in schools, but there is far less attention for the thermal comfort aspects within schools. A literature review is done to clear the effects of thermal quality in schools on the learning performance of the students: it clearly shows that thermal environment is like IAQ of great influence to the students' performance. As many studies focus on the ventilation aspects we focus more on the thermal comfort of the schools through measurements and questioners held in 14 schools equipped with different types of ventilation and heating systems.     

空气湿度对人体热舒适的影响

讨论了在静态热环境下，空气湿度与人体热平衡、皮肤湿润度和人体对衣物的感觉以及人体热舒适之间的关系，分析了湿度瞬态变化对人体平均体表温度、热感觉和热舒适造成的影响。     

An investigation of the influence of ground surface properties and shading on outdoor thermal comfort in a high-altitude residential area

Landscape elements in residential areas can effectively improve the outdoor thermal environment, with different outcomes depending on the climate conditions. This study explores how the ground surface and shading properties affect the outdoor thermal environment in a high-altitude plateau climate where few studies have been conducted. The measurements were conducted during summer and winter in a residential area in Lhasa, Tibet. Without natural shading such as trees, there is a positive correlation between Sky-view factor (SVF) and Physiological equivalent temperature (PET) during winter and a negative correlation during summer. When SVF exceeds 0.65 in summer, it may cause human discomfort. Compared to artificial shading such as a tensioned membrane, deciduous trees are superior at improving human comfort, as they can increase PET by 10.56℃ in winter and decrease it by 9.73℃ in summer. During summer, high-reflection water-permeable bricks can reduce the PET by 1.08℃, and lawns can reduce the mean radiation temperature (Tmrt) by 1.65℃; however, the lawns may produce a microclimate with a high air temperature. The results from this paper can be used as a reference for landscape planning and design in residential areas in highaltitude cold-climate regions.     

Improving outdoor air quality based on building morphology: Numerical investigation

Due to rapid urbanization around the world, high concentrations of vehicular pollutants have deteriorated the outdoor air quality, which can affect the physical and psychological well-being of humans. Numerous strategies have been proposed to overcome these harmful impacts by improving the dispersion of air pollutants. Consequently, a question arises regarding the potential effects of building morphology on the dispersion of pollutants. Subsequently, transient three-dimensional Computational Fluid Dynamics (CFD) simulations are performed to examine the effect of building morphology on PM₁₀ dispersion. Eleven cases with various prototypes and morphological methods are compared with a simple building form to identify the patterns of PM₁₀ dispersion within a given time sequence under a prevailing inflow condition. The results indicate that the different designs of building morphology with varying Relative compactness (R_C) indicator highlight the importance of considering morphological factors to improve outdoor air quality. In addition, the proposed prototypes can reduce PM₁₀ concentrations by approximately 30%–90% at specific points in the studied time sequence. In particular, the vertical, horizontal, and grid folded prototypes can be considered more effective as an approximate decrease between 70% and 90% in PM₁₀ concentrations is observed, which reflects the influence of building morphology on improving outdoor air quality.     

The effect of Urban Heat Island mitigation strategies on outdoor human thermal comfort in the city of Baghdad

Todays, most Iraqi cities suffer from extremely hot-dry climate for long periods throughout the year. However, most urban patterns that exist inside these cities are not suitable for this harsh conditions and lead to an increase in the value of the Urban Heat Island (UHI) index. Consequently, this will increase outdoor human thermal discomfort as well as energy consumption and air pollution in cities. This study attempts to evaluate the effect of UHI mitigation strategies on outdoor human thermal comfort in three different common types of urban patterns in the biggest and most populated city in Iraq, Baghdad. Three different mitigation strategies are used here – vegetation, cool materials, and urban geometry – to build 18 different scenarios. Three-dimensional numerical software ENVI-met 4.2 is utilised to analyse and assess the studied parameters. The input data for simulations process are based on two meteorological stations in Baghdad: Iraqi Meteorological Organization & Seismology, and Iraqi Agrometeorological Network. All measurements are taken in a pedestrian walkway. The results of different scenarios are compared based on their effect on human thermal comfort. Outdoor thermal comfort is assessed according to Predicted Mean Vote index, as mentioned in ISO 7730 standard. This study provides a better understanding of the role of UHI mitigation strategies on human thermal comfort in the outdoor spaces of Baghdad's residential neighbourhoods. This can help generate guidelines of urban design and planning practices for better thermal performance in hot and dry cities.     

Impact of urban geometry on outdoor thermal comfort and air quality from field measurements in Curitiba,Brazil

Urban climate can have severe impacts on people who use outdoor spaces within a city. In its essence, urban climate is directly linked to the configuration of street axes, building heights and their attributes. Thus, the role of urban planners can be crucial for guaranteeing outdoor thermal comfort and air quality in open spaces. This paper presents observed and estimated relations between urban morphology and changes in microclimate and air quality within a city center. Two approaches are presented, showing results of field measurements and urban climate simulations using the ENVI-met software suite. From measured microclimatic data and comfort surveys, carried out in downtown Curitiba, Brazil, the impact of street geometry on ambient temperatures and on daytime pedestrian comfort levels was evaluated, using the sky-view factor (SVF) as indicator of the complexity of the urban geometry. The impact of street orientation relative to prevailing winds and the resulting effects of ventilation (air speed and spatial distribution) on the dispersion of traffic-generated air pollutants were additionally analyzed by means of computer simulations. Results show the impact of urban geometry on human thermal comfort in pedestrian streets and on the outcomes of pollutant dispersion scenarios.     

On the use of bioclimatic architecture principles in order to improve thermal comfort conditions in outdoor spaces

The present paper describes a process for designing and applying several techniques based on bioclimatic architecture criteria and on passive cooling and energy conservation principles in order to improve the thermal comfort conditions in an outdoor space location located in the Great Athens area. For that reason, the thermal comfort conditions in 12 different outdoor space points in the experimented location have been calculated using two different thermal comfort bioclimatic indices developed to be used for outdoor spaces. The used indices were the following: (a) “Comfa”, which is based on estimating the energy budget of a person in an outdoor environment and (b) “thermal sensation”, based on the satisfaction or dissatisfaction sensation under the prevailing climatic conditions of the outdoor spaces. Calculations were performed during the summer period and two different scenarios of the constructed space parameters have been considered. The first scenario consists of a conventionally constructed space, while the second one includes various architectural improvements according to the bioclimatic design principles. The two bioclimatic indicators were used for calculating the outdoor thermal comfort conditions in the above-mentioned outdoor space locations for both scenarios and the effect of the bioclimatic design architectural improvements on the human thermal comfort sensation was presented and analysed.     

关于"热舒适"的讨论

指出了人体热反应研究中关于热舒适的一些模糊概念及对热舒适与热感觉关系的含混认识。分析了热舒适与热感觉的不同含义、现有的不同解释及两者的稳态和动态条件下的差别。     

Outdoor thermal comfort: Analyzing the impact of urban configurations on the thermal performance of street canyons in the humid subtropical climate of Sydney

The quality of outdoor space is becoming increasingly important with the growing rate of urbanization. Visual, acoustic, and thermal balance degradation are all negative impacts associated with outdoor comfort in dense urban fabrics. Urban morphology thus needs assessment and optimization to ensure favorable outdoor thermal comfort (OTC). This study aims to evaluate the thermal performance of streets in residential zones of Liverpool, NSW, Australia, and tries to improve their comfort index (Physiological Equivalent Temperature) to reveal optimum urban configurations. This evaluation is done by investigating the following urban design factors affecting OTC using computational simulation techniques: street orientation, aspect ratio, building typology, and surface coverage. Our findings reveal that street canyon orientation is the most influential factor (46.42%), followed by aspect ratio (30.59%). Among the influential meteorological parameters (air temperature, wind speed, humidity and solar radiation), wind velocity had the most significant impact on the thermal comfort of the outdoor spaces in this coastal region, which typically experiences intense airflow. The results of our analysis can be utilized by multiple stakeholders, allowing them to understand and extract the most vital design factors which contextually influence the thermal comfort of outdoor spaces. Outdoor thermal comfort has a direct effect on the health and wellbeing of occupants of outdoor spaces.     

The role of adaptive thermal comfort in the prediction of the thermal performance of a modern mixed-mode office building in the UK under climate change

Climate change is becoming a serious issue for the construction industry, since the time scales at which climate change takes place can be expected to show a true impact on the thermal performance of buildings and HVAC systems. In predicting this future building performance by means of building simulation, the underlying assumptions regarding thermal comfort conditions and the related heating, ventilating and air conditioning (HVAC) control set points become important. This article studies the thermal performance of a reference office building with mixed-mode ventilation in the UK, using static and adaptive thermal approaches, for a series of time horizons (2020, 2050 and 2080). Results demonstrate the importance of the implementation of adaptive thermal comfort models, and underpin the case for its use in climate change impact studies. Adaptive thermal comfort can also be used by building designers to make buildings more resilient towards change.     

关于热感觉和热舒适与热适应性的讨论

系统地论述了人体热舒适研究的发展过程,讨论了热感觉、热舒适及热适应的定义,并分析了热感觉与热舒适的差异及与热适应性的关系,得出了人们对同一热环境有不同的热感觉及热舒适性,主要是由于人体的适应性产生的。