Evaluation of microclimates and thermal perceptions in urban precincts

The fast pace of urbanisation has led to more built up spaces in many urbanised areas. Urbanised areas influence surrounding microclimates, which in turn, affect users’ thermal perceptions, well- being and outdoor usage patterns. Thermal comfort, which has been extensively studied and used for indoor spaces such as offices and residential buildings, is one of the measures used to assess outdoor spaces. In the absence of outdoor thermal comfort standards, the researchers studying thermal comfort in outdoor urban areas have begun to take advantage of the standards developed for indoor conditions (ISO 7730 2006, ASHRAE 55 2010) to assess outdoor thermal perceptions. However, there are some debates about the adequacy of such standards in various contexts including indoor and outdoor conditions. Some thermal comfort literature has emphasized on the necessity for revising the ‘philosophy’ that forms the comfort standards, which was the stance of the adaptive approach to thermal comfort. In contrast to heat balance theories, the adaptive thermal comfort model includes some influential contextual factors in the assessment of thermal comfort. Australia and particularly Melbourne, capital city of Victoria, is one of the world’s major education providers. Each year many students are admitted to Australian universities and the number of local and international students is expected to rise in the future. The resultant urbanisation in Australia’s cities has created modified meteorological conditions affecting people’s thermal comfort. A university campus attended by people from different climatic backgrounds represents an environment with varying thermal expectations and preferences, providing a great opportunity to investigate the extent of influence of contextual factors on people’s thermal perceptions and applicability of the existing standards. Consequently, this study was carried out at the RMIT University City Campus, an educational urban precinct located in the heart of Melbourne’s central business district (CBD). This study developed a research hypothesis, “existing thermal comfort standards are not adequate to assess the determinants of outdoor thermal comfort conditions”, to investigate the applicability of the assumptions enshrined in the thermal comfort standards in the context of educational urban precincts in Melbourne. Accordingly, three research questions were formulated to navigate the research: (1) to what extent are the thermal comfort standards applicable to educational urban precincts in Australian cities? (2) to what extent can contextual factors influence outdoor users’ thermal perceptions? and (3) what are the factors influencing usage patterns and behaviours in educational outdoor spaces? To investigate people’s interaction with thermal conditions in outdoor built environments, three rounds of field surveys (spring 2014, summer 2015, and autumn 2015) were conducted. Field surveys consisted of questionnaire surveys and concurrent measurements of four environmental parameters that are best known to have the most impact on people’s thermal subjective assessment: air temperature (Ta), relative humidity (RH), wind speed (Va) and radiant temperature (Tg). The questionnaire was structured according to ISO 7730, ASHRAE 55, and ISO 10551 and aimed to capture people’s thermal perceptions (including thermal sensation, preference, acceptability, and overall comfort). Three thermal comfort indices, namely Physiological Equivalent Temperature (PET), Outdoor Thermal Climate Index (UTCI) and Outdoor Standard Effective Temperature (OUT-SET*) were employed to predict thermal comfort conditions using the four thermal factors and two personal parameters (level of activity and clothing insulation). In total, 1059 questionnaires were collected from the three sites of RUCC. The findings on usage pattern of study sites showed that “time of the day” and “weather conditions” were the two major determinants of people’s outdoor attendance. The results revealed that the main assumptions regarding the orthodoxy of thermal comfort (thermal neutrality/neutral temperature1 and acceptable thermal range2) being based on thermal sensation scale was not applicable to the context of an education precinct in Melbourne. Instead, the derivative of thermal preference scale (preferred temperature3) was found to be a better representative of people’s thermal satisfaction and thus thermal acceptance. Therefore, a multi-model research framework was developed to understand the discrepancy between the patterns of observed comfort data and recommendations enshrined in standards regarding thermal satisfaction. This framework consisted of “Socio-ecological system model (SESM)”, “theory of Alliesthesia” and “theory of rising expectations”. The modified version of SESM in this study assumes that several contextual factors clustered under five environments (individual, social, physical, psychological, and standards and guidelines) influence people’s thermal sensations. The results obtained from the analyses of SESM environments suggested that in total, 12 out of 29 contextspecific factors were identified as having a medium impact on people’s thermal sensations. The findings are in line with the notion of adaptive comfort theory according to which non-thermal factors can influence people’s thermal expectations, preferences, and thus their thermal satisfaction. The psychological concept of “Alliesthesia” was used to explain the noticeable variations found in the people’s preferred temperature in different seasons. This concept refers to the notion of “thermal pleasure” whereby people prefer an opposite thermal status once they have had enough experience of current thermal conditions, since repeated exposure diminishes its desirability over time. In other words, people perceive a warm or cold stimulus to be pleasant or unpleasant when their body core temperature is above or under normal conditions. In winter, people yearn for the warmer conditions of the summer months, while in the heat of summer, they yearn for cooler winter conditions. The last component of this framework, “rising expectations”, justified higher thermal expectations of people interviewed in this study (local and international students studying in an Australian university) by referring to their tendency to set greater life standards including higher thermal expectations. According to this theory, when there are some improvements in people’s quality of life, they tend to get used to it and even raise it; dissatisfaction occurs when there is a failure in constant provision of such ideal conditions. Highlighting the inadequacy of current thermal comfort standards, this study attempted to indicate the need for revisiting such standards whereby the results of comfort assessments will be better representative of thermal comfort requirements in real world conditions. The accurate definition of thermal comfort requirements will provide a platform to improve outdoor thermal conditions and advance other related disciplines, including but not limited to, urban design, planning, urban meteorology, and health and safety

Assessment of urban physical features on summer thermal perceptions using the local climate zone classification

Urbanisation has changed local meteorological conditions worldwide. The physical features of outdoor spaces are critical in determining outdoor thermal comfort through changes in meteorological parameters. Past studies comparing subjective thermal perception between local climate zones (LCZ) were mainly conducted in humid subtropical regions. This study aims to investigate this relationship using outdoor thermal comfort survey data collected in three research projects in Melbourne, Australia (temperate oceanic climate) (n = 4717). The physical features investigated included the sky view factor (SVF) and LCZ classification. During Melbourne's summer, people preferred a higher PET value than neutral PET across all LCZs. People in urban green spaces (LCZs B and C) were more likely to feel ‘neutral’ when Physiological Equivalent Temperature (PET) was 15.5 °C–24.5 °C and less likely to feel ‘slightly warm to hot’ when PET was 24.6 °C–55.6 °C. Furthermore, LCZ 6 (LCZ C) reported the highest (lowest) percentage of unacceptable votes. Cluster analysis identified two thermal comfort patterns (neutral and warm groups) representing various thermal sensations and preferences. The thermal comfort patterns proportion differed between built LCZs (5, 6) and land cover LCZs (B, C). Logistic regression revealed that PET values and urban morphology (i.e., LCZ) contributed significantly to people's thermal sensations and acceptability for neutral and warm groups. SVF significantly predicted the thermal sensation and acceptability for the warm group but not the neutral group. Our study approach informs further research to understand the implications of urban design in outdoor spaces using thermal comfort patterns as a benchmark

Evaluating assumptions of scales for subjective assessment of thermal environments – Do laypersons perceive them the way, we researchers believe?

People's subjective response to any thermal environment is commonly investigated by using rating scales describing the degree of thermal sensation, comfort, and acceptability. Subsequent analyses of results collected in this way rely on the assumption that specific distances between verbal anchors placed on the scale exist and that relationships between verbal anchors from different dimensions that are assessed (e.g. thermal sensation and comfort) do not change. Another inherent assumption is that such scales are independent of the context in which they are used (climate zone, season, etc.). Despite their use worldwide, there is indication that contextual differences influence the way the scales are perceived and therefore question the reliability of the scales’ interpretation. To address this issue, a large international collaborative questionnaire study was conducted in 26 countries, using 21 different languages, which led to a dataset of 8225 questionnaires. Results, analysed by means of robust statistical techniques, revealed that only a subset of the responses are in accordance with the mentioned assumptions. Significant differences appeared between groups of participants in their perception of the scales, both in relation to distances of the anchors and relationships between scales. It was also found that respondents’ interpretations of scales changed with contextual factors, such as climate, season, and language. These findings highlight the need to carefully consider context-dependent factors in interpreting and reporting results from thermal comfort studies or post-occupancy evaluations, as well as to revisit the use of rating scales and the analysis methods used in thermal comfort studies to improve their reliability

The Scales Project, a cross-national dataset on the interpretation of thermal perception scales

Thermal discomfort is one of the main triggers for occupants’ interactions with components of the built environment such as adjustments of thermostats and/or opening windows and strongly related to the energy use in buildings. Understanding causes for thermal (dis-)comfort is crucial for design and operation of any type of building. The assessment of human thermal perception through rating scales, for example in post-occupancy studies, has been applied for several decades; however, long-existing assumptions related to these rating scales had been questioned by several researchers. The aim of this study was to gain deeper knowledge on contextual influences on the interpretation of thermal perception scales and their verbal anchors by survey participants. A questionnaire was designed and consequently applied in 21 language versions. These surveys were conducted in 57 cities in 30 countries resulting in a dataset containing responses from 8225 participants. The database offers potential for further analysis in the areas of building design and operation, psycho-physical relationships between human perception and the built environment, and linguistic analyses

The Scales Project, a cross-national dataset on the interpretation of thermal perception scales

Thermal discomfort is one of the main triggers for occupants' interactions with components of the built environment such as adjustments of thermostats and/or opening windows and strongly related to the energy use in buildings. Understanding causes for thermal (dis-)comfort is crucial for design and operation of any type of building. The assessment of human thermal perception through rating scales, for example in post-occupancy studies, has been applied for several decades; however, long-existing assumptions related to these rating scales had been questioned by several researchers. The aim of this study was to gain deeper knowledge on contextual influences on the interpretation of thermal perception scales and their verbal anchors by survey participants. A questionnaire was designed and consequently applied in 21 language versions. These surveys were conducted in 57 cities in 30 countries resulting in a dataset containing responses from 8225 participants. The database offers potential for further analysis in the areas of building design and operation, psycho-physical relationships between human perception and the built environment, and linguistic analyses

Thermal comfort in urban spaces: a cross-cultural study in the hot arid climate

This cross-cultural research is an inaugural attempt to investigate the outdoor thermal comfort and the effect of cultural and social differences in hot arid climates. Case studies were carefully selected in two different parts of the world (Marrakech in North Africa and Phoenix, Arizona, in North America) to represent two different cultures in similar climatic context. Field surveys, carried out during winter and summer, included structured interviews with a standard questionnaire, observations and microclimatic monitoring. The results demonstrate a wide thermal comfort zone and prevalence of air-conditioning influencing thermal comfort requirements. The work also provides evidence of substantial cross-cultural differences in thermal comfort requirements between residents in Marrakech and Phoenix. It shows that adaptive measures, such as level of clothing, changing place, cold drinks consumption and thermal experience, varies between cultures and this influences the thermal evaluation of visitors in outdoor spaces in the hot arid climate. Evidence between the time spent in outdoor spaces and thermal expectations has been found. Moreover, environmental variables such as air temperature and solar radiation have a great impact on the use of the outdoor spaces in the hot arid climate and may determine the number of people in urban spaces. The study also identified significant differences in thermal comfort requirements between different socio-economic groups, highlighting the need for comfortable open spaces

Socio-economic Factors for the Perception of Outdoor Thermal Environments: Towards Climate-sensitive Urban Design

recent decades a number of parameters have influenced outdoor thermal conditions in cities worldwide. These influential parameters should be investigated to identify the consequences of such changes in human thermal perception. Following the understanding of the magnitude of effect of each factor, urban design policy makers gain a clear insight into the design of outdoor settings that are appropriate or tailored to meet the specific requirements of outdoor environment users. The fundamental notion of such framework lies within the concept of climate-sensitive design. In assessing the outdoor thermal comfort, the research, to date, has tended to focus more on thermal factors than non-thermal ones to explain users' thermal perception, behaviour and usage pattern in outdoor settings. It has now been evident that the role of non-thermal factors in thermal perception are of particular importance considering differing cultural, climatic, geographical and socio-economic contexts. Among non-thermal factors, socio-economic elements can take a decisive role in the perception of outdoor thermal environments. Nevertheless, the persistent lack of full understanding of the inter-relationship between these factors and definition of socio-economic factors causes misconception among the investigators as well as decision makers. This paper tries to position the socio-economic factors in outdoor thermal comfort studies through introducing the elements impacting the thermal perception keeping aside the thermal factors,. Positioning such factors includes a model that elaborates the eliciting information on these non-quantifiable factors and provides a framework for ensuring that the climate-sensitive design of outdoor places needs to become a key aspect of urban planning and design

The effect of individual and social environments on the users thermal perceptions of educational urban precincts

Assessment of outdoor thermal comfort provides a valuable insight into the performance outdoor built environments. During the last four decades the number of the thermal comfort studies focused on the impact of microclimate parameters on human health and wellbeing has increased. Meanwhile, advances in the thermal comfort studies have expanded to include non-thermal factors including the social and individual parameters indirectly interacting with thermal perceptions. These factors are believed to be contextual-based and this study aimed to understand their effects on the outdoor thermal perceptions in educational outdoor spaces. The data used in this study was collected during three rounds of the field surveys consisting of measurement and questionnaire surveys. The field surveys were conducted in three case studies which were the premises of a university campus in Melbourne, Australia, from November 2014 to May 2015. Using a socio-ecological system model (SESM) as the research framework, this study aimed to investigate the role of non-thermal factors that are classified under the individual environment (gender, age group, exposure to sun, level of activity and clothing insulation, skin colour) and the social environment (position, companionship and cultural background). The analytical results demonstrated the medium and low influence of individual and social environments on outdoor thermal sensation, respectively. The research outcome is specific to thermal comfort requirements in the educational precincts but also can apply to similar climate and contextual conditions. The results may be used to inform decisions made in the phase of design and planning for development of educational outdoor spaces

Study of thermal satisfaction in an Australian education precinct

This study aimed to understand the role of thermal expectations in achieving thermal comfort in outdoor spaces. Three open spaces in an educational precinct located in the temperate setting of Australia were selected as case study sites to explore how thermal expectations may affect people's thermal responses to outdoor micrometeorological conditions. Three types of data collection methods including questionnaire survey, field measurement and on-site observations were employed to collect thermal comfort information in three consecutive seasons (November 2014, February 2015, and May 2015). Three measures of thermal satisfaction (preferred temperature, neutral temperature, and acceptable thermal range) extracted from people's thermal preferences and sensations were used to analyse the field survey data, determine thermal comfort requirements, and examine thermal stress in the study context. A multi-model theoretical framework was then adopted to explain the pattern of thermal satisfaction among the target population. This framework consisted of three models: "Socio-ecological system model (SESM)", "theory of Alliesthesia" and "theory of rising expectations". The study demonstrated the efficiency of above-mentioned framework to explore thermal comfort requirements in an educational precinct. Overall, the results challenged the validity of equivalency of thermal neutrality and thermal satisfaction enshrined in comfort standards in the study context

Perception of wind in open spaces

Dense urbanization influences the livability of cities. Changes in local meteorological conditions can be adverse for human health and well-being. In urban open spaces, it is widely known that changes in building density and configuration in cities influence wind speed (Va). This influence modifies latent heat flux between the human body and surrounding environment and thereby affecting the thermal comfort conditions in open spaces between buildings. Several studies have demonstrated the significant effect of wind speed on outdoor thermal comfort. Melbournes Central Business District (CBD) has recently experienced dense urbanization and this pattern of development has instigated noticeable changes in meteorological conditions. Some evidence has suggested that the patterns of wind flow induce thermal discomfort during cool seasons. Conversely, the wind is most welcomed during warm seasons. This study was conducted to assess outdoor users responses to Va in three open spaces of an educational precinct in Melbournes CBD. The open spaces studied are different in terms of design and function. Users responses and meteorological conditions were examined through a series of field measurements and questionnaire surveys from November 2014 to May 2015. This study used three perceptual scales to analyze participants experience of Va during field surveys: Bedford preference, thermal sensation and personal acceptability. Analytical results yielded the wind perceptual comfort thresholds for different seasons as well as the entire study period. The results suggested that in addition to the geometry of the urban open space, the function of place could influence peoples perceptions of Va. The research findings contribute to developing thermally comfortable outdoor environments