Thermal Comfort In Urban Spaces Research Articles

The thermal perception of outdoor urban spaces in a hot arid climate: A structural equation modelling (SEM) approach

Human thermal comfort is linked to multi-sensory attributes and psychological cognition besides the influence of prominent meteorological parameters. To date, even the most advanced thermal comfort models like UTCI consider the interaction between human and external surroundings to be a heat transfer problem applying thermodynamic equations in the derivation behind thermal comfort indices. Machine learning (ML) models offer the advantage of improving the accuracy of predictor variable, but they fail to determine the relationship between the independent variables and data-driven prediction models. Structural Equation Modelling (SEM), an advanced modelling technique, can expose all hidden relationships among variables using latent variables while not being data-driven like ML. This study aimed to develop a structural framework which systematically explains these relationships and quantify the effects of 24 variables on outdoor thermal comfort using SEM due to its ability to represents the response of the dependent variable to a unit change in an explanatory variable. The method employed 635 structured interviews, observations, and wide-ranging micrometeorological measurements conducted concurrently in three Pedestrianized urban alleys in Cairo. The model statistically confirmed the hypothesis that overall thermal comfort in urban spaces is significantly influenced by multiple factors. Of these, background microclimatic conditions had the greatest relevance and certain urban features the least. 1 unit increase microclimate leads to a change in thermal comfort by 0.423 and 0.349 in summer and winter, respectively. In terms of thermal perception, the model shows that individuals are willing to tolerate a wider range if certain urban features are present such as shaded seating opportunities. These outcomes may aid to provide important guidance for urban designers to enhance thermal perception in urban streets.

Investigating the impact of using modified cool materials by titanium dioxide (TiO2)-based photocatalytic self-cleaning nanoparticles in urban facades on urban microclimate parameters

PurposeOn the one hand, one of the most important global strategies to improve thermal comfort in urban spaces is using cool materials (high albedo materials) in urban facades. On the other hand, using cool materials in urban facades is a big challenge. Over time, the albedo of cool materials that modified by titanium dioxide (TiO2)-based photocatalytic self-cleaning materials (PSTiO2) does not decrease. In fact, its self-cleaning property prevents the loss of the initial albedo of the material. The self-cleaning performance of these materials was investigated in previous researches. However, their thermal performance in urban space has not been investigated yet. This paper studied the performance of these materials on the urban square facade. Design/methodology/approachThe thermal performance of PSTiO2 on the thermal comfort of the urban square was evaluated by ENVI-met(v4). The results simulated by ENVI-met software with field measurements in the urban Square were compared. Field measurements of air temperature were conducted on 22 July and 30 March. FindingsThe results showed that these materials, despite their self-cleaning properties, have significant thermal impact in the urban environment. Using plaster modified by PSTiO2 (albedo 0.6) improved slightly by nearly 0.2 °C the thermal comfort of the urban square. Whereas, white paint modified by PSTiO2 (albedo 0.9) reduced the physiologically equivalent temperature (PET) by 0.5 °C, because reflection of solar radiation increased between the buildings facades. The simulation results showed that due to the space is more enclosed in the square entrance, the mean radiant temperature (Tmrt) increased. As a result, PET index rose too. Originality/valueThis study shows that employing cool and self-cleaning materials in the urban facades of Jolfa Square, in addition to have self-cleaning property, is effective in the amount of thermal comfort of the square. In the parts of the square where the enclosure is less, an improvement in thermal comfort was observed. The performance of the cool and self-cleaning materials in the facade in terms of thermal comfort is completely dependent on the physical parameters of the urban space.

Cross-evaluation of thermal comfort in semi-outdoor spaces according to geometry in Southern Spain

Climatic events in Mediterranean cities, such as heat waves, directly affect their inhabitants. As a result, outdoor thermal comfort in urban spaces is gaining increasing research attention because it is associated with the quality of life in these cities. Significant improvements have been achieved in the adaptation of buildings; however, a similar level of resilience to climate is not observed in urban spaces.This research proposes quantifying thermal comfort in semi-outdoor enclosed spaces according to EN16798, UTCI and PET. The study is carried out in different cities in southern Spain, employing 20 courtyards with different geometries. Results reveal courtyards as liveable rooms during most hours of the day in summer. The influence of its geometry considering AR is decisive since the impact of outdoor climate on the microclimate of the courtyard depends on it, exceeding values of 60% comfort hours (PET and EN16798) in all case studies during the warm season. When AR > 3, the courtyard reaches comfort 90–100% of the hours of the day and approximately 70–80% when the AR 2–3. In the case of the most common geometries in Mediterranean cities, with AR 1–2, >70% of the hours the courtyards are within the limits of comfort.

Assessment of urban heat islands and thermal discomfort in the Amazonia biome in Brazil: A case study of Manaus city

The urban heat island (UHI) is an important phenomenon due to its direct and indirect impacts on the health of the population residing in urban environments. Very few studies have been conducted on the relationships between UHI and outdoor thermal comfort in the Amazonia biome. In this work, we analyzed the behavior of hourly variability of the UHI, heat index (HI), thermal discomfort, and Land Surface Temperature (LST) in Manaus (Brazil). The novelty of the study is to assess the degree of alteration of the UHI with changes in vegetation cover in the Amazon biome. Temperature and air humidity data were collected from six weather stations from July 2013 to July 2014. In addition, satellite images of the TM and OLI/TIRS sensors onboard the Landsat 5 and Landsat 8 satellites for the years 1987, 1998, 2007, and 2015 were used. The intensity of the UHI increased during the analyzed period. The weather stations located in the urban area had temperatures above 30.0 °C, while the temperatures in the rural area ranged from 25.0 to 26.5 °C. As a direct implication of the results found, it is noted that in Manaus, the UHI can reduce thermal comfort in urban spaces, directly impacting people's quality of life and health. The periods with the least amount of precipitation in the city (August and September) can generate thermal discomfort inside houses during the night period, meaning an increase in the number of hours in which people are exposed to heat.

Outdoor thermal comfort enhancement using various vegetation species and materials (case study: Delgosha Garden, Iran)

Urban gardens bring various benefits including environmental, social, and cultural values to citizens around the world. Since thermally comfortable these gardens promote the quality of urban living, a plethora of studies have been conducted to extend the existing knowledge of outdoor thermal comfort. The present study intended to evaluate outdoor thermal comfort conditions in the microclimate of the urban historic garden of Urmia, Iran, for both summer and winter. Along with performing field measurements at the site based on Taghvaei's model of “Fundamental Values and Factors of Landscape (FVFL)”, a questionnaire survey was used to determine the outdoor thermal comfort range of users. Then, the ENVI-met software was used to properly simulate the factors in summer and winter. The results of the questionnaire and simulation were compared with each other and necessary solutions were presented according to previous studies to improve outdoor thermal comfort in urban spaces. The results showed that the concrete with a high-albedo, trees with wide crowns and tall trunks (Platanus and Pine), and the use of sufficient water were proposed as the optimal solution for summer. Also, asphalt with the high-albedo, Cypress, and Populus trees in winter have been considered as a suitable solution to improve the outdoors thermal comfort of Urmia city. It is expected that future studies will evaluate the effects of the results in various green urban environments and provide a practical framework for landscape architects and urban planners.

Implications of urban space aspect ratio on campus outdoor thermal comfort ( Case study, BUE campus, Cairo, Egypt)

Campus outdoor urban spaces consider effective spaces for students to take a walk or engage in recreation and social activities or studying. A comfortable thermal environment is extremely important for students to enjoy the outdoor urban spaces. Wherefore thermal comfort in urban spaces is a crucial issue, but the warmer urban climate may have some negative impacts on outdoor thermal comfort of student in campus. Therefore, the aim of this study was to investigate the effect of aspect ratio of urban space, which is one of most effective strategy to improvement outdoor thermal comfort. ENVI-met numerical simulation applied to examine a series of aspect ratio scenarios. ENVI-met run for main entrance space in BUE campus, Cairo, Egypt. The effects of aspect ratio on outdoor thermal comfort dealt with in detail. The results show that aspect ratio (H/W=3) could be considered starting point to respect outdoor thermal comfort.

The structural model for thermal comfort based on perceptions individuals in open urban spaces

Thermal comfort in urban spaces has gain significance in recent years. So far, thermal comfort has been evaluated through observing and recording climatic data. This study aims at evaluating thermal comfort using perceptions of individuals as the main users of open urban spaces. It aimed to develop a structural model to rank environmental and climatic factors in order of their significance and impact on thermal comfort within open urban spaces through structural equations modeling (SEM) using partial least squares (PLS). To this end, 500 questionnaires were distributed among experts in this area, and the completed questionnaires were collected and analyzed. According to the results, air temperature, wind speed, relative humidity, and radiation temperature had the greatest impact on outdoor thermal comfort. In contrast, the emissivity of materials and placement in open spaces, surface transparency, and material texture had the least impact on thermal comfort in open urban spaces. The importance of this research work is further highlighted considering the role of presence in open urban spaces in the quality of life and the significant impact of thermal comfort on the improved quality of such spaces. The urban specialists, especially experts of open urban spaces, may use the results of this study to take measures for improving the quality of life of citizens.

MICROCLIMA Y CONFORT TËRMICO

El presente artículo presenta una revisión de la literatura existente en cuanto al diseño de espacios urbanos, microclima y confort térmico urbano. El microclima y confort térmico en espacios urbanos, especialmente en las ciudades localizadas en regiones tropicales, debe ser abordada a partir de los conceptos y teorías que permiten comprender la incidencia de los parámetros microclimáticos y tejido urbano sobre la sensación de confort térmico y bioclimatización de los espacios urbanos. De esta forma, en este documento se manifiesta la significación de la planificación, el diseño urbano y microclima de una ciudad en regiones tropicales, explorando la clasificación de las zonas climáticas locales a nivel urbano, la isla de calor urbana, el confort térmico urbano, los parámetros microclimáticos como temperatura del aire, humedad relativa, viento, radiación solar e iluminación natural, la vegetación y su caracterización en espacios urbanos y la morfología de una ciudad.

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

The article was published without issue designation resulting in regular issue compilation.

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.

An ordered probability model for predicting outdoor thermal comfort

Outdoor thermal comfort in urban spaces is gaining increasing research attention because it is associated with the quality of life in cities. This paper presents an ordered probability model for predicting the probability distribution of thermal sensation votes (TSVs) based on 1549 observations obtained from a large-scale field survey conducted at a park in Tianjin, China. With a given set of inputs, the developed model can predict the probability that people will feel cold, cool, slightly cool, neutral, slightly warm, warm, or hot. The predictive capability of the ordered probability model was systematically assessed by comparing it with the survey data and a traditional multivariate linear model. Both models had a similar accuracy in predicting single-value TSVs. However, the ordered probability model performed much better than the multivariate linear model in predicting the probability distribution of TSVs. A sensitivity analysis of the ordered probability model revealed that outdoor air temperature was the most important influencing factor. The impacts of global radiation, relative humidity, and activity level on predicted thermal sensation depended on the outdoor air temperature. The developed ordered probability model was used to predict suitable time periods for holding outdoor activities in Tianjin across a whole year. This new model is a more informative tool for predicting outdoor thermal comfort.

Urban Heat Island and Park Cool Island Intensities in the Coastal City of Aracaju, North-Eastern Brazil

In this study, an evaluation of the Urban Heat Island (UHI) and Park Cool Island (PCI) intensities in Aracaju, North-Eastern Brazil, was performed. The basis of our evaluation is a 2-year dataset from the urban climatological network installed with the principles and concepts defined for urban areas related to climatic scales, sitting and exposure, urban morphology, and metadata. The current findings update UHI intensities in Aracaju refuting the trend registered in previous studies. On average, the UHI was more intense in the cool season (1.3 °C) than in hot season (0.5 °C), which was caused by wind speed decrease. In relation to the PCI, mitigation of high air temperatures of 1.5–2 °C on average was registered in the city. However, the urban park is not always cooler than the surrounding built environment. Consistent long-term monitoring in the cities is very important to provide more accurate climatic information about the UHI and PCI to be applied in urban planning properly, e.g., to provide pleasant thermal comfort in urban spaces.

Green Roof Effects in a Case Study of Rome (Italy)

Abstract Outdoor thermal comfort in urban spaces is an important goal that contributes to pedestrians’ health. Urban heat island (UHI) is a phenomenon tightly associated with the development of cities and urban expansion. Its effect is defined as the increase of the urban air temperature compared to surrounding rural areas. Its characteristics has vast impacts and implications on energy efficiency, environment, and at last human comfort and health. The urban density and the design of built and natural environments of cities play a crucial role in defining sustainable patterns. In the last years many studies on different mitigation techniqueswere carried out. The main mitigation techniques are the improving of green spaces and the use coolmaterials. In this studyit was analysed the effects of green roof in a case study situated in Rome (Italy).

Daytime thermal comfort in urban spaces: A field study in Brazil

This article presents the results from thermal comfort surveys in two squares located in the city of Belo Horizonte, Brazil over two different seasons. Objective environmental parameters were compared with subjective responses collected during field surveys in order to evaluate thermal comfort conditions people experience and identify potential thermal adaptation processes. Individuals and behavioral’ characteristics were also taken into account. The summer survey was carried out in March 2013 and the winter survey in July 2013, both comprising a total of 1693 interviewees. The PET index was calibrated to determine the thermally acceptable range. Neutral and preferred temperatures, for both summer and winter, were obtained in order to assess thermal preference. The results show that people were more tolerant in one of the squares (Liberdade square) in winter, considering the same thermal conditions. These findings were associated to psychological processes related to thermal adaptation, such as naturalness, perceived control, experience (thermal history on longer timescales – seasonal) and environmental diversity - along with the presence of greater adaptive opportunities. The calibration of the PET index, resulted in the definition of the thermal acceptability range of: “Cold” for PET values bellow 19 °C; “Neutral” for PET values between 19 °C and 27 °C; “Hot” for PET values greater than 27 °C. Neutral temperatures were 27.7 °C, in summer, and 15.9 °C, in winter; while preferred temperatures were 14.9 °C, in summer, and 20.9 °C, in winter. Design strategies, such as shading, exposure to the wind and providing increased environmental diversity may improve urban environments and pedestrians' experience in cities.

Effect of Street Design on Outdoor Thermal Comfort in an Urban Street in Singapore

AbstractOutdoor thermal comfort in urban spaces is an important indicator of the quality of life in an urban environment. This paper attempts to investigate the effect of street design on outdoor thermal comfort in an urban street in the central business district in Singapore, focusing on the design variables of street orientation, height-to-width ratio (H/W), and vegetation. A comprehensive field measurement with multiple points is presented and used to validate a widely used computer software holistic microclimate modeling system. The significance of the research is that real field data from multiple measurement points on microclimate parameters are produced and the effect of street design parameters on outdoor thermal comfort is quantified. It is found in the paper that the NW-SE oriented street is more stressful than the NE-SW street in the afternoon in terms of thermal comfort in Singapore, and that a H/W of 3 can be considered a threshold with respect to outdoor thermal comfort. The paper concludes ...

Thermal Comfort in High-rise Urban Environments in Singapore

Outdoor thermal comfort in urban spaces is an important indicator of the quality of life in urban environment. This paper attempts to investigate outdoor thermal comfort in an urban street surrounded by high-rise commercial buildings in the central business district in Singapore, focusing on the effect of height-to-width ratio (H/W) on outdoor thermal comfort. The microclimatic parameters of different H/W scenarios were determined by ENVI-met numerical simulation. Field measurement was conducted to validate the results from the numerical simulation and they were in good agreement. The physiologically equivalent temperature (PET) was utilized as the thermal index to assess outdoor thermal comfort. It has been approved quantitatively that shading provided by high aspect ratios can improve outdoor thermal comfort in urban streets and H/W of 3 can be considered as a threshold with respect to outdoor thermal comfort in Singapore.

Outdoor thermal comfort within five different urban forms in the Netherlands

Outdoor thermal comfort in urban spaces is known as an important contributor to pedestrians' health. The urban microclimate is also important more generally through its influence on urban air quality and the energy use of buildings. These issues are likely to become more acute as increased urbanisation and climate change exacerbate the urban heat island effect. Careful urban planning, however, may be able to provide for cooler urban environments. Different urban forms provide different microclimates with different comfort situations for pedestrians. In this paper, singular East–West and North–South, linear East–West and North–South, and a courtyard form were analysed for the hottest day so far in the temperate climate of the Netherlands (19th June 2000 with the maximum 33 °C air temperature). ENVI-met was used for simulating outdoor air temperature, mean radiant temperature, wind speed and relative humidity whereas RayMan was used for converting these data into Physiological Equivalent Temperature (PET). The models with different compactness provided different thermal environments. The results demonstrate that duration of direct sun and mean radiant temperature, which are influenced by urban form, play the most important role in thermal comfort. This paper also shows that the courtyard provides the most comfortable microclimate in the Netherlands in June compared to the other studied urban forms. The results are validated through a field measurement and calibration.

Heat in courtyards: A validated and calibrated parametric study of heat mitigation strategies for urban courtyards in the Netherlands

Outdoor thermal comfort in urban spaces is an important contributor to pedestrians’ health. A parametric study into different geometries and orientations of urban courtyard blocks in the Netherlands was therefore conducted for the hottest day in the Dutch reference year (19th June 2000 with the maximum 33°C air temperature). The study also considered the most severe climate scenario for the Netherlands for the year 2050. Three urban heat mitigation strategies that moderate the microclimate of the courtyards were investigated: changing the albedo of the facades of the urban blocks, including water ponds and including urban vegetation. The results showed that a north–south canyon orientation provides the shortest and the east–west direction the longest duration of direct sun at the centre of the courtyards. Moreover, increasing the albedo of the facades actually increased the mean radiant temperature in a closed urban layout such as a courtyard. In contrast, using a water pool and urban vegetation cooled the microclimates; providing further evidence of their promise as strategies for cooling cities. The results are validated through a field measurement and calibration.

Climatic design and assimilation of activity spaces (case study on Soheil residential complex in 19th district of Tehran)

Using the principles of climatic design, the most basic inactive energy preparation, would serve as a principled strategy to minimise energy cost and attain thermal comfort in urban spaces. In this study, Soheil residential complex on a plot of 9207 square metres of land in 19th district of Tehran has been studied as a case study to access thermal comfort in an urban space. Also, the main objective of this research is finding a framework and model that can provide all inactive energy preparations serving the goal. So, the climatic data were collected from Mehrabad weather station. Then, the Eco-tect and Climate Consultant 5.2 softwares were used firstly to draw up a general framework of space design or intended sphere in order to analyse the way that the climatic elements affected site design and determine the areas in which masses were located. Finally, the quality of the performance of climatic factors in the intended spheres was tested and assessed in the ENVI-met.4 software through assimilation with a...

Thermal comfort in urban spaces: impact of vegetation growth: Case study: Piazza della Scienza, Milan, Italy

This paper reports on a study on the evolutionary impact of vegetation in a newly built square in Milan designed by V. Gregotti. The aim of the work is to evaluate the impact of vegetation growth on users’ comfort. The methodology adopted involves: sets of field measures (air and radiant temperature, wind velocity and relative humidity); a simplified thermal comfort evaluation with the energy budget method COMFA; and a scenario for the vegetation growth. When trees become adult we can observe different phenomena. The shading effect under an aged tree canopy clearly shows a reduction of the absorbed radiation by users, generating an energy budget very close to comfort (under 50 W/m 2) even with a high air temperature. In the case of points exposed to direct sunlight all day long, tree growth reveals two phenomena of the global radiation absorbed by a user: (1) reduction, by the tree screening effect, of absorption of the diffuse solar global radiation, and (2) increase, by the elevation of the objects viewed in the sky hemisphere, in absorption of the terrestrial radiation.