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Abstract

Thermal comfort in the built environment is a crucial factor impacting health, well-being, and productivity of urban dwellers. Accordingly, comprehensive analyses are needed to ensure that acceptable criteria of thermal comfort are defined and met in urban environments. The main objective of this study is to define such performance metrics and quality measures of outdoor thermal comfort (OTC), aiming to inform climate-conscious urban design. This article first discusses the motivations for introducing comprehensive thermal comfort metrics, addressing the shortcomings of conventional OTC evaluations that neglect the temporal or spatial variability of OTC. It then introduces four performance metrics, which collectively inform urban planners and designers on the performance of outdoor space with regards to thermal comfort. These metrics build upon the concept of “autonomy” previously introduced for indoor spaces and are extended to include the unique characteristics of outdoor thermal comfort. Second, we discuss the capability of these metrics given the limitations of modeling tools available for urban microclimate analysis, and evaluate the critical factors for an accurate evaluation of Outdoor Thermal Comfort Autonomy (OTCA). We observe that the spatial distribution of airflow at the pedestrian height is critical for OTCA calculation, while the consideration of realistic surface heating depends on the urban density. Lastly, we present an example of employing weather clustering methods such that OTC performance metrics are achieved on an annual basis in a comprehensive yet efficient way. By discussing the capability and the limitations of these metrics we aim to promote climate-conscious design using metrics that are tangible and accessible to non-simulationexperts.

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... The weather file climatic data and the microclimatic data generated through Urban Weather Generator (UWG) [25] were used for the wind speed and the surface temperature simulations performed through the grasshopper plug-ins Eddy [26] and Honeybee of Ladybug Tools [27], respectively. The first used the Computational Fluid Dynamics (CFD) software OpenFOAM [28] and the latter used the energy simulation software EnergyPlus [29] to finally assess outdoor comfort using the Universal Thermal Climate Index (UTCI) [30] and the Outdoor Thermal Comfort Autonomy (OTCA) [31] metrics. ...
... The analysis of the outdoor thermal comfort and the assessment of the potential of the vegetated surfaces and trees to provide comfort was performed using the UTCI [30] thermal index and the OTCA [31] temporal and spatial method. The assessments were performed using analysis grids of the same size as the wind and surface temperature simulations, considering the center points of the cells at 1.5 m from the ground as human body locations. ...
... This is defined as the ratio of an outdoor space that meets the comfort criteria for at least 50% of the occupied time. The threshold to consider an area comfortable depends on the activities, e.g., for dining terraces a threshold of 80% is suggested due to the difficulty of rearranging the layout of tables according to variable microclimatic conditions, whereas for generic outdoor activities for which people can change location inside the area 50% is considered acceptable [31]. Thus, the automated algorithm determined the area to be covered either only by the vegetated surface or also by the trees, i.e., the vegetation to ground ratio to achieve 50% of the area in state of comfort for 50% of the occupied time according to the UTCI index. ...
Chapter
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Cities are one of the major contributors of climate change. The built environment urgently needs to significantly reduce its impact on resource depletion and its CO2 emissions. At the same time, urban environments must adapt to guarantee livability and safety in increasingly frequent severe conditions. To aid this process, assessment methods and indexes have been developed to help designers and researchers investigate optimal solutions for outdoor thermal comfort. Temperature increase during summer is a growing concern also in northern European cities such as Tallinn, Estonia. This paper presents a study on the comfort conditions of the outdoor areas of the TalTech campus in Tallinn during summer and investigates the cooling potential of vegetated surfaces and trees in the local microclimate. A parametric design workflow was developed that integrates building and climate modeling, environmental and building simulations and outdoor comfort assessment through the metrics of Universal Thermal Climate Index and Outdoor Thermal Comfort Autonomy. The results show that heat stress can be experienced on the outdoor areas of the campus. The quantity and the optimal location of vegetated surfaces and trees to provide comfort were determined through the developed algorithm. The methods and the generated vegetation patterns are presented and discussed.
... These indexes have been used to report outdoor thermal comfort for different time of the day and different locations. However, Nazarian et al. (2019) presented a comprehensive set of metrics for urban design performance with respect to outdoor thermal comfort. These consider the temporal and spatial variability of outdoor thermal comfort and can be used for comparative studies or the evaluation of different urban design scenarios in different meteorological conditions. ...
... • Continuous OTCA (CntOTCA), is an extension of Spatial OTCA such that partial credit is given in an outdoor space where OTCA is lower than 50% of the year • Thermal stress indicator (TSI), is the average deviation of the thermal comfort index (i.e. PET) from the acceptable OTC range in an outdoor space calculated during a year Precise description of the calculation method of these metrics can be found in Nazarian et al. (2019) and also in the Supplementary Material of this manuscript. Since our study is focused on Singapore, the thermal acceptability criteria was selected from Heng and Chow (2019) as PET in the range of 21.6 • C to 31.6 • C. ...
... In this work we have carried out a detailed spatial-temporal analysis of the impact of different urban geometries on the OTC levels by using specific indices presented in Nazarian et al. (2019). By means of modelling techniques, different scenarios of block form, street orientation, aspect ratio, and building height profile have been evaluated for a high-rise urban development in a tropical context (Singapore). ...
Article
Tropical cities are exposed to high air temperature and relative humidity throughout the year, causing pedestrian thermal discomfort. In this work, we present an evaluation of the impact of urban geometry on the outdoor thermal comfort (OTC) in Singapore, focusing on a new mixed-use high-rise development. Different urban design strategies/scenarios have been analyzed: two block forms, four street orientations (N-S, E-W, NE-SW, NW-SE), four street aspect ratios (from 1.5 to 3.5) and three building height profiles (arrangement of buildings based on height). The study is based on modelling techniques. Each scenario was analyzed for seven representative weather conditions during the year. The results are analyzed with specific metrics that take into account the spatial and temporal OTC variations. The results are conditioned by prevailing low winds and high frequency of cloudy days. The best OTC levels are observed on high street aspect ratios (2.5-3) and on N-S oriented streets. Although, on a yearly perspective the streets oriented NE-SW show the worst OTC performance, deviation from the acceptable range is not high. Higher differences between street orientations are encountered for specific weather types. The outcomes provide adequate urban parameters for high-rise developments to improve OTC in hot and humid tropical regions.
... Many OTC models and indices have been developed (see de Freitas & Grigorieva, 2015 for a summary of those indices) and widely used for developing urban design guidelines and methods (Aminipouri et al., 2019;Nazarian et al., 2019;Nevat et al., 2020a). Importantly, there is a need to connect the objective OTC indices to the perception of the population which may be subjective and depends on many factors (Rupp et al., 2015;Chong et al., 2019). ...
... We show that this uncertainty can be integrated into our model, by introducing the notion of Probabilistic Impact Function which incorporates this uncertainty in a rigorous mathematical way. By doing so, we extend previous deterministic models, such as the ones presented in Nazarian et al. (2019), Nevat et al. (2020aNevat et al. ( , 2020b, Santos et al. (2021). ...
... Note that unlike previous works on this topic who used a deterministic impact function (Nevat et al., 2020a(Nevat et al., , 2020bNazarian et al., 2019), in our case the impact function is probabilistic, since we incorporate the uncertainty coming from the finite sample used in the survey. In fact, this function can be interpreted as a random variable which follows the Bernoulli distribution. ...
Article
Full-text available
We develop a new framework for selecting an urban design which performs best from an Outdoor Thermal Comfort (OTC) perspective, while taking into account the uncertainty in the OTC preference of individuals. To this end, we first present and develop the notion of Probabilistic Acceptability Criterion (PAC) which is a new method to quantify people’s satisfaction of OTC values, based on data collected from a survey. We develop the PAC for both regression and classification models which are most common statistical analysis methods in the literature. Next, based on the PAC, we develop a new approach to scoring each of the urban designs, based on Binary Probabilistic Impact Function, which extends the widely used deterministic impact function. We show that the score is a random variable which follows a Poisson-Binomial distribution and characterise its parameters. We then use those results and present a new approach for scoring of the urban designs that is based on the Sharpe ratio, which is a widely used metric in financial applications. Our framework is the first model which provides urban designers the ability to evaluate the quality of their urban designs from an OTC point of view, while taking the uncertainty into account in a holistic and rigorous way. We illustrate our framework by applying it to a real case study in Singapore.
... For each scenario, cold (December 22-28) and hot (August 10-16) weeks were selected as representative simulation periods for this study. A quality measure of OTCA (Nazarian, Acero, & Norford, 2019), was selected as the performance metric for comparison between scenarios. Although Standard Effective Temperature (SET) (Nazarian et al., 2019) and Physiological Equivalent Temperature (PET) were selected as evaluation metrics in Nazarian et al. (2019) and Acero, Koh, Ruefenacht, & Norford (2021), we instead used UTCA in this study. ...
... A quality measure of OTCA (Nazarian, Acero, & Norford, 2019), was selected as the performance metric for comparison between scenarios. Although Standard Effective Temperature (SET) (Nazarian et al., 2019) and Physiological Equivalent Temperature (PET) were selected as evaluation metrics in Nazarian et al. (2019) and Acero, Koh, Ruefenacht, & Norford (2021), we instead used UTCA in this study. A modified version of OTCA called Spatial OTCA (SpOTCA) is defined as "the percentage of an outdoor space that is within the desired thermal comfort range at least 50% of the occupied time (over a year or a prescribed period of use)" by Nazarian et al. (2019). ...
... A quality measure of OTCA (Nazarian, Acero, & Norford, 2019), was selected as the performance metric for comparison between scenarios. Although Standard Effective Temperature (SET) (Nazarian et al., 2019) and Physiological Equivalent Temperature (PET) were selected as evaluation metrics in Nazarian et al. (2019) and Acero, Koh, Ruefenacht, & Norford (2021), we instead used UTCA in this study. A modified version of OTCA called Spatial OTCA (SpOTCA) is defined as "the percentage of an outdoor space that is within the desired thermal comfort range at least 50% of the occupied time (over a year or a prescribed period of use)" by Nazarian et al. (2019). ...
Article
In the physics-based simulation of urban geometries, the outdoor environment was usually simulated separately from buildings – until recently, when the holistic assessment of the urban environment began to attract more attention. Although analyzing design alternatives with multiple objectives is still a challenge, computational tools enable generating thousands of scenarios to rapidly assess performance corresponding to a specific goal. In this study, we developed a multi-phase optimization framework for conceptual urban design. We tested this framework for urban typologies in Syracuse. The energy performance of each alternative was compared with a baseline. The alternatives that generate wasteful energy performance were filtered out first, then remaining scenarios that performed better than the baseline were analyzed using outdoor thermal comfort autonomy (OTCA). Mid-rise multifamily buildings showed the best performance (55.8% energy improvement compared to the baseline). Although hot week outdoor comfort satisfaction among selected mid-rise typologies was high (92.9–98.5%), the satisfaction in cold week was very low (between 8.4–11.6%) among them. This framework contributes to identifying an acceptable range of design solutions by broadening the perspective of the field toward using a more customized optimization framework in early design that will further guarantee the requirements of energy efficient and sustainable cities.
... To assess the temporally dynamic UTWE, the maximum, minimum, and average of the assessment indices per unit time within a certain period were frequently used in the reviewed studies [12,13,98]. Nazarian et al. proposed three indices to evaluate the percentage of thermal comfort period or average deviation from the thermal comfort condition in the occupied period, including the outdoor thermal comfort autonomy (OTCA), the thermal stress indicator, and the weighted outdoor thermal comfort autonomy [145]. ...
... proposed spatial and continuous OTCA to evaluate the proportion of thermal comfort areas in the space of interest [145]. The assessment indices at a specific point were also used to represent the UTWE of the surrounding areas [99]. ...
Article
The urban thermal and wind environment (UTWE) has become a major concern in urban planning design. Consideration of the UTWE involves steps of modelling, assessment, and improvement on multiple scales. However, the method specifications of each step on different scales are unclear, and a comprehensive review of relevant studies is thus required. On this basis, the modelling, assessment, and improvement methods of the UTWE are comprehensively reviewed according to their applicable scales. The review indicates that the scale is systematically considered by studies of the UTWE modelling and improvement, but not by studies of UTWE assessment. On the meso-scale, the UTWE of plot units are usually evaluated in isolation and the interactions among them are neglected. Studies of the UTWE improvement cover urban morphology, urban green and blue infrastructure, and urban materials, but some of their conclusions contradict each other. Current UTWE assessments cannot directly guide the selection of proper improvement strategies. In the future, studies of the UTWE improvement may be based on urban typologies such as the Local Climate Zone, and the data-driven approaches provide an opportunity to link the results of UTWE assessment and the corresponding improvement strategies.
... Both sDA and LM have the benefit of offering a reliable one-number performance indicator for daylight and energy balancing, respectively. The spatial version of the newly introduced Outdoor Thermal Comfort Autonomy (OTCA) metric (Nazarian, Acero, & Norford, 2019), provides a similar indication for outdoor comfort indices (e.g. UTCI). ...
... For each iteration, Grasshopper was used to sample results from a grid of test points (four meters dense and one meter high) in the public spaces surrounding the plot (Fig. 2 bottom left), for each hour for both a typical cold (7th of January) and a hot day (7th of July). To calculate one number which would serve as a basis for comparison between scenarios, the OTCA metric (Nazarian et al., 2019) is adopted here. This metric represents the percentage of hours across the evaluated time frame (in this case 8:00-18:00) which are not in thermal stress (9°-26°according to the UTCI scale). ...
Article
Despite the urgent global call for an energy transition and the promotion of health and well-being in cities, a holistic approach to evaluating the trade-offs between an urban energy balance and environmental quality considerations is lacking. This paper bridges this gap by introducing a Grasshopper digital workflow through which the impacts of a wide range of building and urban design parameters on both energy performance and environmental quality can be effectively evaluated. This workflow is tested here for both theoretical and site-specific urban test cases in the context of Tel Aviv. For these test cases, the performance metrics - energy load match, spatial daylight autonomy and universal thermal climate index - were calculated using EnergyPlus, Radiance and ENVI-met simulation engines for different block typologies and were then analyzed. The results showed that among the block typologies, the courtyard achieved the optimal combination across the tested environmental criteria, despite the daylight and energy generation penalty associated with self-shading in compact block typologies. This workflow highlights the performative tradeoffs between energy and environmental quality considerations and can thus help urban designers achieve not only a lower environmental impact but also regenerative and healthier design outcomes.
... Since these performance metrics are basically designed for indoor spaces, cannot fully address the complexity of spatial modelling in outdoor spaces, especially large-scale areas. Recently, a new study has evaluated the thermal comfort performance of outdoor spaces by introducing new tempo-spatial performance metrics (Nazarian et al., 2019). However, application of these performance metrics to investigate the performance of outdoor spaces still requires more attention. ...
... Urban Climate 33 (2020) 100665 calculations ignore the difference between the slight level of discomfort and extreme heat/cold stress from an acceptable range of thermal comfort by classifying the studied areas to two categories, either comfort or discomfort. Such assumptions without considering the deviation from the comfort range result in an overestimation of discomfort hours and poor understanding of the thermal performance of an outdoor area (Nazarian et al., 2019). Using the deviation analysis provides a better understanding of the thermal comfort distribution by determining the extent of deviation of thermal comfort values from an acceptable comfort range for each location. ...
Article
Over-urbanization negatively affects on urban temperatures and results in the formation of urban heat islands. Outdoor thermal comfort (OTC) occurs in such exacerbated conditions, influencing health, well-being, and productivity of urban dwellers. Therefore, cities need to urgently evaluate the OTC and act to ensure providing acceptable OTC in built-up settings. As such, many studies envisaged to understand outdoor thermal performance of urban environments based on their geometrical features and suggest mitigation strategies against the negative effects of heat stress. Reviewing the literature reveals that most of the previous studies are focused on the urban scenarios of a single canyon or a limited number of individual buildings with simplified and uniform geometrical features without including the effect of surrounding urban neighborhoods. Furthermore, most studies only calculate OTC at a certain time and location in the space where field measurements are conducted. Since these field measurements are scattered in time and space, the comprehensive tempo-spatial distributions of OTC cannot be achieved to have a comprehensive understanding of outdoor environments performance. In this regards, the OTC tempo-spatial visualization is essential in outdoor environments. This study aims to develop a framework to comprehensively evaluate the performance of OTC and assess the effect of geometrical features on the spatial and temporal distribution of thermal comfort in residential neighbourhoods. The proposed framework is applied to the case study of Tehran city where three residential urban configurations are selected with different geometrical features (organic, orthogonal and apartments block) to conduct a series of high-resolution simulations. This study follows a step by step process to understand the impact of built-up urban areas on their thermal comfort performance: (1) development of 3-D models of three selected neighborhoods, (2) tempo-spatial OTC analysis, (3), and understanding the impact of geometrical parameters on the thermal comfort performance. The study reveals that all the selected areas have a significant deviation from the acceptable comfort range with mostly moderate and strong heat stress. The differences in OTC performance of these areas is related to the geometrical features of buildings and canyons including neighborhood layout and proportion of open and built-up areas and canyons’ profiles (building’ height, aspect ratio and orientation). The spatial variation of OTC is more significant in orthogonal areas and apartment complexes while organic settings provide a less distributive comfort performance with lower hours of heat stress and discomfort. Results show that the cooling effect of organic neighborhoods is higher due to the higher rate of aspect ratio in canyons. Orthogonal and apartment cases have higher mean radiant temperature mostly above 40°C. In the apartment complex, open spaces show the highest rate of heat stress, due to the long exposure to shortwave solar radiation. In this area, the most important domain of retrofitting strategies should be focused on landscape planning for green planting and water bodies. The results of this study help to identify design solutions that should be incorporated in the planning studies and as a result, a holistic perspective would be achieved for better decision-making via this tempo-spatial comprehensive analysis.
... Since these performance metrics are basically designed for indoor spaces, cannot fully address the complexity of spatial modelling in outdoor spaces, especially large-scale areas. Recently, a new study has evaluated the thermal comfort performance of outdoor spaces by introducing new tempo-spatial performance metrics (Nazarian et al., 2019). However, application of these performance metrics to investigate the performance of outdoor spaces still requires more attention. ...
... Urban Climate 33 (2020) 100665 calculations ignore the difference between the slight level of discomfort and extreme heat/cold stress from an acceptable range of thermal comfort by classifying the studied areas to two categories, either comfort or discomfort. Such assumptions without considering the deviation from the comfort range result in an overestimation of discomfort hours and poor understanding of the thermal performance of an outdoor area (Nazarian et al., 2019). Using the deviation analysis provides a better understanding of the thermal comfort distribution by determining the extent of deviation of thermal comfort values from an acceptable comfort range for each location. ...
Article
Outdoor thermal comfort (OTC) has a significant effect on the health and well-being of urban dwellers. One of the key factors contributing to the tempo-spatial variation of thermal comfort in urban neighbourhoods is the geometrical characteristics. This paper develops a novel modelling framework to comprehensively evaluate the tempo-spatial thermal comfort performance of neighbourhoods on the basis of geometrical features. A weighted temporal thermal comfort performance (TCPw) metric is furthermore proposed to translate the thermal comfort results to a comparative performance criterion. Universal thermal climate index (UTCI) is the index chosen as baseline for assessing this metric. To demonstrate the practicality of the developed framework, three urban areas with different morphological character in climate zone of Tehran are investigated. Different geometrical variables of these locations are initially extracted from existing datasets using geographic information systems (GIS). A high-resolution spatial model is then developed to simulate thermal comfort of the neighbourhoods by coupling an energy simulation model (EnergyPlus) and a thermal comfort plugin (Ladybug). The model is successfully validated against a series of in-situ measurement data. Results indicate that differences in comfort performance are related to the simultaneous effects of neighbourhoods' layout (density, open areas), and street canyons' profiles (aspect ratio, orientation).
... This approach was applied here on a theoretical urban model, consisting of nine square urban blocks in a homogeneous grid configuration, with a constant street width of 20 m. i.e. the Floor Area Ratio (FAR), which represents the ration of total floor area to the site area, was used here to create the density scenarios by changing the number of floors in each typology. Similar parametric and theoretical model approaches were used extensively in other studies on urban environmental performance both by this author [21,38,39] and others [40][41][42]. The computational workflow for this analysis (Fig. 1) was conducted employing the Grasshopper parametric interface [23]; in Grasshopper, the geometrical, climatic as well as other relevant simulation data (e.g. ...
... This calculation was conducted using the Ladybug_Outdoor Comfort Calculator component which is based on the polynomial approximation method by Bröde et al. [60]. To achieve an effective outdoor thermal comfort quantification across each model, the Outdoor Thermal Comfort Autonomy (OTCA) metric [41] was calculated for each point. The OTCA stands for the percentage of hours in a certain period (from a given day up to one year) between certain hours of the day, in which UTCI values are in the 'no thermal stress' temperature band (i.e. between 9 and 26°C). ...
Article
With the rise of awareness of health and well-being in cities, urban environmental analysis should expand from energy performance to new environmental quality-based considerations. The limited potential to annually evaluate outdoor thermal comfort, predominant among these considerations, has restricted the exploration of the interrelations between urban morphology and annual energy performance. This study aims to bridge this gap by capitalizing on the new capabilities of Eddy3D – a Grasshopper plugin which enables effective calculations of hourly microclimatic wind factors via OpenFOAM which in turn are used to generate annual outdoor thermal comfort plots. Using this method, a parametric study was conducted for different typology and density scenarios in three different hot climatic contexts in Israel. The automated analytical workflow evaluated a total of 60 design iterations for their energy balance, outdoor thermal comfort autonomy (OTCA) and self-shading levels using the shade index. The high correlation found here between the annual shade index and the OTCA, across all climatic contexts, shows the potential of the shade index to serve as an effective indicator, in these contexts, for comparative or optimization outdoor comfort studies. Further results are both the superiority of the courtyard typology in both energy and outdoor comfort studies, and the contrasting impact of higher density on the annual energy balance (lower performance) and outdoor thermal comfort (higher performance) in hot climates. The annual plots of both the energy balance and OTCA reveal various seasonal and monthly trends in the three different climatic zones which can lead to localized and seasonal urban design strategies.
... For example, in climate-based daylight modelling, daylight autonomy (DA) is a metric used to describe the percentage of the occupied times of the year when the minimum illuminance requirement is met by daylight alone [21]. By the same token, Outdoor Thermal Comfort Autonomy (OTCA) is a metric used to describe the percentage of occupied times of the year during which a designated area meets a set of thermal comfort acceptability criteria [22], as per the formula: ...
... OTCA is not currently a feature offered by ENVI-met, so the authors created a Python script that post-processes its results via the NetCDF library for Python [23]. In addition to producing OTCA heat maps, the script is also capable of reporting Spatial Outdoor Thermal Comfort Autonomy (sOTCA), which describes the percentage of a designated area which meets the thermal comfort acceptability criteria for at least 50% of the occupied period [22]. Used in combination, OTCA and sOTCA form the basis for the rapid and comprehensive assessment of outdoor space (Figure 7). ...
Article
Full-text available
In the context of global climate change, it is increasingly important for architects to understand the effects of their interventions on indoor and outdoor thermal comfort. New microclimate analysis tools which are gaining appreciation among architects enable the assessment of different design options in terms of biometeorological parameters, such as the Universal Thermal Climate Index (UTCI) and the Outdoor Thermal Comfort Autonomy. This paper reflects on some recent experiences of an architectural design office attempting to incorporate local climatic considerations as a design driver in projects. The investigation shows that most of the available tools for advanced climatic modelling have been developed for research purposes and are not optimized for architectural and urban design; consequently, they require adaptations and modifications to extend their functionality or to achieve interoperability with software commonly used by architects. For this scope, project-specific Python scripts used to extract design-consequential information from simulation results, as well as to construct meteorological boundary conditions for microclimate simulations, are presented. This study describes the obstacles encountered while implementing microclimate analysis in an architectural office and the measures taken to overcome them. Finally, the benefits of this form of analysis are discussed.
... For example, in climate-based daylight modelling, daylight autonomy (DA) is a metric used to describe the percentage of the occupied times of the year when the minimum illuminance requirement is met by daylight alone [21]. By the same token, Outdoor Thermal Comfort Autonomy (OTCA) is a metric used to describe the percentage of occupied times of the year during which a designated area meets a set of thermal comfort acceptability criteria [22], as per the formula: ...
... OTCA is not currently a feature offered by ENVI-met, so the authors created a Python script that post-processes its results via the NetCDF library for Python [23]. In addition to producing OTCA heat maps, the script is also capable of reporting Spatial Outdoor Thermal Comfort Autonomy (sOTCA), which describes the percentage of a designated area which meets the thermal comfort acceptability criteria for at least 50% of the occupied period [22]. Used in combination, OTCA and sOTCA form the basis for the rapid and comprehensive assessment of outdoor space (Figure 7). ...
Article
Full-text available
In the context of global climate change, it is increasingly important for architects to understand the effects of their interventions on indoor and outdoor thermal comfort. New microclimate analysis tools which are gaining appreciation among architects enable the assessment of different design options in terms of biometeorological parameters, such as the Universal Thermal Climate Index (UTCI) and the Outdoor Thermal Comfort Autonomy. This paper reflects on some recent experiences of an architectural design office attempting to incorporate local climatic considerations as a design driver in projects. The investigation shows that most of the available tools for advanced climatic modelling have been developed for research purposes and are not optimized for architectural and urban design; consequently, they require adaptations and modifications to extend their functionality or to achieve interoperability with software commonly used by architects. For this scope, project-specific Python scripts used to extract design-consequential information from simulation results, as well as to construct meteorological boundary conditions for microclimate simulations, are presented. This study describes the obstacles encountered while implementing microclimate analysis in an architectural office and the measures taken to overcome them. Finally, the benefits of this form of analysis are discussed.
... Thereby, many such schemes fail to provide the basic level of thermal comfort required. Further, many studies have observed that due to poor planning of layouts and spatial arrangements, the houses have often observed to be overheated (Ali & Patnaik, 2018;Chen et al., 2018;Nazarian et al., 2019;Wang et al., 2019). Studies in low-income housing settlements across the country have shown that the majority of the occupants are dissatisfied with the thermal environments and comfort levels provided . ...
Technical Report
In India, the planning and design of low-income housing has historically been dominated by politics with cost of the unit and quantity being prioritized over quality and comfort. In a country that experiences different climatic conditions throughout the year, buildings need to be responsive to the local climate that helps in improving the thermal comfort of the inhabitants. The need for such intuitive planning and design become all the more relevant in places like Vijayawada where the ambient temperature is above 30 degrees for more than half of the year. Further, the thermal environments in the informal sector are often neglected while planning and design of low-income housing settlements. This case study is focused on understanding, mapping and drawing planning & design guidelines for accessing and improving the thermal conditions of New Rajarajeswari Peta a low-income rehabilitated housing settlement in Vijayawada. Archetype characterization of case area was carried out and eighteen archetypes were narrowed down for further documentation and thermal perception study. Documenta-tion of building for recreating virtual models of case houses were carried out through primary survey. Qualitative interviews on selected cases were performed along with recording thermal sensation votes. Testo-480 and ther-mal imager camera were used for measuring temperature, humidity, air velocity and iso-thermal images respec-tively, during the course of documentation. DesignBuilder and GIS were used for simulating thermal environ-ment and mapping the case area respectively. The results indicate that as much as three-degree temperature change can be archived by changing the layout, opening sizes, increasing ventilation rate and material properties of these houses, in confirmation with other similar studies (Lau et al., 2019). Further, the perception of heat in low-income housing settlement had varied response as against the general perception. The findings of the study shall help the architects, planners and decision makers in making a informed design decisions while planning and designing of low-income housing settlements.
... Nowadays, the indoor environmental quality in buildings is assuming greater importance [1], due to the need for efficient energy performance in an emerging scenario where the key issue is now the climate change. The use of perforated metal screens as a protective skin in façades can be very useful for this purpose [2,3]. Over recent years, the behaviour of double-skin façades has been highlighted in residential buildings with such methods as technological enclosures with passive thermal control [4], solar façades [5], dynamic windows [6], and naturally ventilated façades [7,8]. ...
Article
Double-skin perforated sheet façades, enclosures consisting of perforated screens, air chambers and glass/wall sheets, are features of modern building design that are winning greater acceptance. A detailed analysis of their suitability across Europe is first performed here. A reference building both with and without the protective double-skin perforated sheet envelope is subjected to a comparative test of solar energy gains with regard to the environment. Additionally, the results of a preliminary survey are presented on the visual perceptions of different patterns of perforated metal sheets. Then the behaviour of these configurations is addressed, through a complete “Energyplus® model” (design builder). A test campaign on a reference perforated screen mounted on a service building of reference was fully monitored over one year, supported by thermographic data recorded for additional validation purposes during the same period. The new parametric energy assessment takes additional variables into account, such as orientation and location of the façade, demonstrating that the real performance for such enclosures greatly depends on them. Accordingly, the influence of different combinations of perforated screens on cooling, heating and lighting loads demonstrates the suitability of a previously optimized configuration in terms of relative energy savings.
... However, building design needs to be fundamentally responsive to the local climate, particularly in low-income housing settlements (Taleghani M, 2018). Due to poor planning of layouts and spatial arrangements, housing units in this kind of projects are often exposed to a tendency of overheating (Ali et al., 2018;Chen et al., 2018;Nazarian et al., 2019;Wang J. et al., 2019). Studies in low-income housing settlements across the country show that most occupants are dissatisfied with the thermal environments and the achieved comfort levels. ...
Article
Full-text available
Rising temperatures due to climate change and urban heat island effects lead to heat stress and need remedial actions at all city planning scales. The design of built spaces strongly influences residents' exposure to heat risks. However, practices that increase communities' resilience to heat are not yet influencing decision-making in urban planning. In this study, qualitative interviews were conducted in low-income households in three different cities in India and Austria to understand residents' strategies for coping with excess summer heat in their homes. Although significant differences are discernible between India and Austria, low-income households in both continents lack agency over their housing situation and have little means to adapt it to heat. This lack strongly influences how they can handle the heat. Lack of resources forces them to accept unfavourable thermal conditions and keeps them from affording any but the most basic remedies. While buildings constitute the single most important and effective means of protection against heat stress for most interviewees in India, design restrictions and the appliance of cheap building materials limit this protection's effectiveness, especially during evening and night times.
... ) according to the intended usage of the urban space to improve its outdoor thermal comfort autonomy [78]. For example, streets experiencing large pedestrian traffic during lunch and early evening hours, would likely benefit from a moderate to high if they are located in dense low-rise (LCZ3) or open mid-rise areas (LCZ5). ...
Article
An increase in urban vegetation is an often proposed mitigation strategy to reduce urban heat and improve outdoor thermal comfort (OTC). Vegetation can alter urban microclimate through changes in air temperature, mean radiant temperature, humidity, and wind speed. In this study, we model how street tree and ground vegetation cover and their structural, optical, interception, and physiological traits control the diurnal cycle of OTC in different urban densities in a tropical city (Singapore). For this purpose, we perform a variance based sensitivity analysis of the urban ecohydrological model UT&C. Model performance is evaluated through a comparison with local microclimate measurements and OTC is assessed with the Universal Thermal Climate Index (UTCI). We find a pronounced daily cycle of vegetation effects on UTCI. Tree cover fraction is more efficient in decreasing UTCI during daytime, while a higher vegetated ground fraction provides more cooling during night. Generally, increasing vegetation cover fractions do not deter OTC, except in certain urban densities during some periods of the day. An increase in tree and ground vegetation fractions provides a higher average UTCI reduction compared to a change in vegetation traits (0.9 – 2.9 °C vs. 0.7 – 1.1 °C during midday, 10 month average). The increase in humidity related to plant transpiration prevents further reduction of UTCI. However, the choice of vegetation traits enhancing tree transpiration can decrease UTCI during hot periods. These results can inform urban planners on the selection of vegetation amount and traits to achieve feasible OTC improvements in tropical cities.
... Existing studies by the first author, developed using the same building clusters and urban areas in Tallinn, show that during the cold season the layout of commercial buildings can also dramatically increase or decrease the thermal discomfort of pedestrians due to the wind chill effect [42]. An annual investigation, merging the winter and summer studies, is a planned extension of the current research, for which new metrics [70] capable of assessing long and multi-seasonal time frames will be used to provide architects and urban planners with guidelines and data to design commercial districts characterized by adequate comfort conditions throughout the whole year. ...
Article
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Considering climate change, controlling outdoor microclimates is an increasingly pressing concern. Microclimates have a significant effect on both outdoor and indoor comfort, and on the energy efficiency of buildings. This concern is particularly important as current climate conditions reveal that warmer summers are threatening the comfort of pedestrians and causing overheating in office environments, which is consequently increasing cooling energy consumption. A further concern is that this trend now extends to Nordic latitudes. Existing literature demonstrates how a local microclimate depends on many factors such as urban density, shape and orientation of buildings, the types of materials present, the number of green areas and anthropogenic activities. However, there is little research focusing on how reciprocal distances among tall buildings, and their relative position, affect outdoor and indoor comfort, and the associated energy consumption of buildings. This paper presents a unique and comprehensive insight into the interconnected nature of indoor and outdoor comfort via coupled simulations. It presents a study of clusters of tall commercial buildings located in the Nordic climate of Tallinn (Estonia) with different microclimates, and shows that the differences are due to variable shadowing and reflections and different wind patterns. The results, which focus on summer conditions, show that small variations of cluster layout strongly affect the local indoor and outdoor comfort, thus highlighting the need to conduct both studies simultaneously in research aiming to increase pedestrian and indoor comfort and resource efficiency.
... The recorded highest day temperature in summer months has an increasing trend. The increasing occurrences of the extreme heatwave in the cities force the city planners to value more about the sustainable usage of urban open environment [2]. And thus, it is calling for a tool or an index for the accurate evaluation of the outdoor thermal comfort conditions, and give accurate evaluations of the strategies for improving the urban thermal environment, such as increasing greenery [3,4], creating shading area [5] and providing a windy environment for the pedestrians by rearranging urban geometry [6,7]. ...
... In this work, thermal comfort will be used to evaluate the livability of different urban environments as a function of their urban morphology, construction materials and presence of green and vegetation. Then, thermal comfort indexes consider physiological and psychological people characteristics that represent their average data [28][29][30][31][32][33][34][35][36]. ...
Article
Extensive and intensive green roofs and vegetated walls should be used to improve the livability in cities, especially in densely built-up context, in order to optimize their contribution on energy savings and greenhouse gas emissions, improving thermal comfort conditions and ensuring a greater storm-water runoff. The aim of this study is to evaluate the effect of urban morphology and to quantify the impact of green surfaces and plants on outdoor thermal comfort conditions. The analysis was applied to six neighborhoods in the city of Turin, identified as typical districts with different building geometries, urban contexts and green presence. The outdoor thermal comfort conditions were assessed calculating a set of indicators, such as the predicted mean vote and the physiological equivalent temperature, with the support of ENVI-met tool. Retrofit scenarios were hypothesized, and outdoor thermal comfort conditions were investigated before and after the installation of green roofs and vegetated areas. The result allowed to understand how thermal comfort vary, considering the building geometry, urban morphology, and green areas in different zones of the city of Turin. By analyzing neighborhoods, it is possible to identify the optimal built environment that ensure better thermal comfort conditions. These models and tools could support urban planners in defining the best measures to improve the liveability and quality in the built environment considering local constraints and the real characteristics of the territory or in designing new neighborhoods. https://www.iieta.org/journals/ti-ijes/paper/10.18280/ti-ijes.652-433
... Field monitoring is the use of relevant measuring instruments for the study site for outdoor meteorological parameters (such as air temperature-T a , relative humidity-RH, black globe temperature-T g , wind speed-v, global solar radiation-G, etc.), and subjective questionnaire surveys are conducted near the monitoring sites [15][16][17][18]. The field monitoring outdoor thermal comfort evaluation method is to find out the comfortable or acceptable thermal conditions for local residents, to understand human body perception of the thermal environment [19][20][21], and to provide valuable reference for urban planners and park designers [9,[22][23][24][25], so as to formulate strategies for optimizing the outdoor thermal environment. ...
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Urban parks are an important component of urban public green space and a public place where a large number of urban residents choose to conduct outdoor activities. An important factor attracting people to visit and stay in urban parks is its outdoor thermal comfort, which is also an important criterion for evaluating the liability of the urban environment. In this study, through field meteorological monitoring and a questionnaire survey, outdoor thermal comfort of different types of landscape space in urban parks in Chengdu, China was studied in winter and summer. Result indicated that (1) different types of landscape spaces have different thermal comforts, (2) air temperature is the most important factor affecting outdoor thermal comfort; (3) because the thermal sensation judgment of outdoor thermal comfort research in Chengdu area, an ASHRAE seven-sites scale can be used; (4) the neutral temperature ranges of Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) in Chengdu in winter and summer were obtained through research; (5) and UTCI is the best index for evaluating outdoor thermal comfort in Chengdu. These findings provide theoretical benchmarks and technical references for urban planners and landscape designers to optimize outdoor thermal comfort in urban areas to establish a more comfortable and healthy living environment for urban residents.
... Cohen's classification was not accepted by all researchers either, as Matthews and colleagues (Matthews, Scott, & Andrey, 2021) also used Humidex below 21°C in rating schemes of their thermal comfort facet, or Zare and colleagues (Zare et al., 2018) also used WBGT to evaluate thermal conditions in the cold months of the year. While using WCT is recommended mostly in areas experiencing seasonal temperatures below 10 °C (Peddie & Soligo, 2020), this index was used even in the tropical climate of Singapore (Nazarian, Acero, & Norford, 2019) or warm regions of China (J. Zhu, Wang, & Huang, 2019). ...
Article
Most of thermal indices were developed based on the European/North American subjects and climates, while they should be investigated in other regions as well. This study aims to improve the applicability of nine thermal indices in Tehran, to be used in heat-health warning systems. 1008 interviews were conducted along with field measurements, and modified scales of thermal indices were determined using three different techniques. The results revealed low percentages of correct predictions for original scales of thermal indices despite having high correlation coefficient with thermal sensation votes–TSV, while modified scales of Universal Thermal Climate Index–UTCI and Physiologically Equivalent Temperature–PET correlated better with TSV and had higher correct predictions percentages than the original scales, especially in the ‘neutral’ class. Also the modified scales determined by ‘Probit analysis’ and ‘PD diagram's fitted curve’ techniques correlated better with TSV than those acquired by ‘linear regression’. Comparing the modified PET and UTCI scales with studies conducted in similar climates revealed differences between the ‘cool’ and ‘cold’ categories, probably caused by cultural issues. The results of this study can help urban and landscape designers to design more comfortable outdoor spaces.
... This provides evidence for the need of a global heat hazard alert system, as heat is not simply impacting one area at a time but many regions simultaneously, even when only considering August as we present here. However, we note that above the 26°C UTCI heat stress threshold is not experienced the same everywhere due to climate and acclimatization, which should be explored further and is only an indication of when one could start experiencing heat stress (Di Napoli et al., 2018;Nazarian et al., 2019). ...
Article
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Heatwaves are increasing in frequency, duration, and intensity due to climate change. They are associated with high mortality rates and cross‐sectional impacts including a reduction in crop yield and power outages. Here we demonstrate that there are large deficiencies in reporting of heatwave impacts in international disasters databases, international organization reports, and climate bulletins. We characterize the distribution of heat stress across the world focusing on August in the Northern Hemisphere, when notably heatwaves have taken place (i.e., 2003, 2010, and 2020) for the last 20 years using the ERA5‐HEAT reanalysis of the Universal Thermal Comfort Index and establish heat stress has grown larger in extent, more so during a heatwave. Comparison of heat stress against the emergency events impacts database and climate reports reveals underreporting of heatwave‐related impacts. This work suggests an internationally agreed protocol should be put in place for impact reporting by organizations and national government, facilitating implementation of preparedness measures, and early warning systems.
... Another point that warrants a discussion is how to leverage better decision aiding for practitioners that use simulation approaches like the ones presented in this manuscript. For this, (Nazarian et al., 2019) proposed a novel way on how to look at outdoor comfort autonomy in an urban area instead of looking at simplified metrics like an annual mean to enable climate-conscious design for practitioners. They propose three metrics: outdoor thermal comfort autonomy (OTCA), spatial and continuous comfort autonomy, and thermal stress indicator. ...
Article
The architectural community needs holistic, evidence-based planning tools to promote urban resilience in the face of global warming. To ensure maximum impact, simulation-driven microclimate analysis methods must be integrated early in the design process. With Eddy3D, we present a toolkit to simulate outdoor thermal comfort (OTC) metrics with a decoupled approach. We motivate the decoupled systems framework with meteorological measurements and local and global sensitivity analyses of three different climates. For a real-world case study on a university campus, we present results for both wind velocity and mean radiant temperature simulations. Finally, we discuss the advantages and disadvantages of a decoupled simulation approach considering design aiding and the architectural. Our findings support reduced simulation time and flexibility, with the caveat of reduced accuracy due to neglecting forced convection, albeit this being less relevant in the early stages of design. The framework presented in this manuscript has been implemented and released as Eddy3D, a plugin for Rhino & Grasshopper.
... Nazarian et al. [15] stated that thermal comfort is a top priority with a direct impact on productivity and cognitive performance, wellbeing, and health of urban dwellers. However, its practical implementation would necessitate comprehensive, accurate, and easy-to-understand evaluations of outdoor thermal comfort. ...
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Green infrastructure is well recognized as a key urban climate mitigation strategy. In line with this, and following a central government decree, Jakarta Municipal Government has created a green infrastructure target of 30% underpinned by a green space weighting factor. This study questions the efficacy of such a “universal” target setting from the point of view of outdoor thermal comfort and demonstrates the basis for an alternative approach. Based on a “new’ green factor developed from a systematic analysis of the literature, thermal comfort simulations of representative local climate zones (LCZ) show that improvements in current green space policy are possible. We enumerate a rational basis for specifying green space targets per local area based on contextual realities as captured by the LCZ approach. Such a nuanced approach to mitigate the human comfort consequences of inadvertent urban growth is not only more contextually appropriate but also enhances the feasibility of achieving the intended goal of urban greening in Jakarta.
... By using the planning system and delivery targets to craft market opportunities, planners are able to influence the actions of others, whilst indirectly enhancing state capacities by creating new subjects to act as partners who develop, finance, and/or implement policies (Jessop, 2016). A growing literature has also emerged in more applied sciences that demonstrates how virtual metrics can assist planners to design more inclusive and public urban spaces, both from technical and more socially-oriented perspectives (Ewing & Clemente, 2013;Nazarian, Acero, & Norford, 2019). There are also attempts, for example, to measure the value of green spaces in cities and urban nature or to develop liveability scores that compare the quality of urban environments (Ahern, Cilliers, & Niemelä, 2014;Carmona, 2020). ...
Article
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In this paper we draw on the findings of a mixed methods research project that has examined the production, regulation, and delivery of housing in London. Our aim is to develop fresh insights into the growing mobilisation of numbers and targets in contemporary planning systems. More specifically, we bring two fields of literature into conversation. First, drawing on recent contributions from Pike et al. (2019) we develop their notion of ‘city statecraft or the art of city government and management of state affairs and relations (p.79). We discuss how and why their framing of contemporary urban governance captures current trends in contemporary cities, including: the financialisation of housing and infrastructure; the rolling-out of delivery-focused public private partnerships; and the broader political projects that underpin planning priorities. The paper combines these insights with wider writings in urban studies on virtualism or the analysis of theories and governmental practices that seek to make the world conform to pre-existing ideas, rather than describing and explaining its formation. We argue that target-based forms of governance represent the implementation of a virtual statecraft in which the material realities of actual places become simulated worlds, ripe for calculation and re-making. We show, through in-depth research on housing regulation and investment/development trends in London, the ways in which virtual forms of statecraft are developed and implemented and with what effects on the material outcomes of urban development processes. The findings are of comparative significance as planning systems across Europe and beyond are becoming increasingly focused on market-oriented oriented forms of planning in an effort to boost the production of housing and to deliver social policy outcomes.
... Due to computational costs and memory storage limitations, an hourly OTC analysis of annual data is impractical. [21] proposed a weather clustering method to describe typical daily patterns -called weather types. The weather types are defined based on features such as wind direction, wind speed, temperature and humidity. ...
Article
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With the increase of temperature, a tropical country like Singapore will face the challenge of mitigating the anthropogenic heat emissions and urban heat storage to maintain its quality of urban life. However, due to the complex nature of climate and urban fabric, it is difficult for urban planners to make climate-sensitive informed decisions on how to achieve better Outdoor Thermal Comfort (OTC) in an intuitive while holistic way. We develop a holistic and principled decision process via an implementation of a decision support tool which interactively visualizes how climatic factors, urban design scenarios, importance of spatial use, and various acceptability criteria impact the OTC assessment in a simple step-by-step manner. The advantage of this tool is that it serves as an agent-based climate-responsive urban design system that presupposes planner’s trust. A complete working example is provided which demonstrates how a user could choose the optimal scenario for a new public housing estate located at the northeast of Singapore.
... In addition to the local meteorology, the street morphology, the presence of vegetation, as well as the underlying surface material and artificial heat are all important factors affecting the urban thermal environment [6,8,19,29,50] . The study of the effects of urban morphology on the thermal environment, which is the focus of this paper, is crucial because it can provide reference for future architectural design and urban planning (see for example [11,16,25,26,35,42,46] ). ...
Article
This paper investigates the correlation between street morphology and thermal environment of six street models representing the central morphology of Barcelona (Spain), Berlin (Germany), London (UK), New York (US), Nanjing (China) and Paris (France). The morphology is first characterized through morpho- logical indices (i.e. opening and closing ratios, smoothness ratio, symmetry ratio) obtained from a novel “street morphology extraction”method, which allows to depict a certain feature of the geometry (the presence of openings, the shape of building envelopes and the symmetry of the street, respectively). It is found that the average Sky View Factor (SVF) is negatively correlated with the building density, the clos- ing ratio and the symmetry ratio, and positively correlated with the opening ratio. Then, air temperature (AT), Mean Radiant Temperature (MRT) and Predicted Mean Vote (PMV) are obtained from ENVI-met sim- ulations to assess how the thermal environment is affected by the street morphology. In particular, the average AT, MRT and PMV are positively correlated with average SVF at 12:00 and with the building den- sity at 21:00. The presence of openings, the shape of building envelopes and the symmetry of the street differently affect the local thermal environment and comfort during the day, leading to different MRT and PMV distribution. For example, the Barcelona model, due to high building density, smoothness and symmetry, which prevent ventilation, experiences slightly warm conditions also in the night. The novel morphometric method proposed allows studying which feature mostly affects the thermal environment and can thus be employed in the early planning stage.
... Methodologically, there are two main approaches to evaluate and estimate thermal comfort conditions in cities: one is a simulation-based approach and the other is based on sensing techniques. The simulation-based methods have been always dependent on computational power available on the hardware system, however, with the advent of cloud computing resources, it is possible to simulate complex and multi-scale urban models with reasonable time effort (Nazarian et al. 2019). Despite that, the current efforts to simulate perceived pedestrian thermal comfort in urban settings is enormous, since the environmental conditions are highly localized and involve phenomena that are time and calculation-intensive to simulate, plus requiring substantial urban data inputs. ...
... Due to the spatial diversity of spaces and the wide range of human activities in cities and consequently the complexity of the parameters affecting outdoor thermal comfort, various studies have been carried out for understanding outdoor thermal comfort conditions (Bayoumi, 2017 Heidari & Monam, 2013;Johansson, Thorsson, Emmanuel, & Krüger, 2014;Nazarian, Acerob, & Norford, 2019;Shevchenko, Snizhko, & Matzarakis, 2020;Tahbaz, Jalilian, & Moosavi, 2012) and numerous perceptual indices have been introduced. These indices have many commonalities and can be categorized into two general groups: experimental and rational. ...
Article
Few, if any, studies have researched the effects of vegetation, water and shading on outdoor thermal comfort in the hot and dry climate. This study identified and examined the effect of kharkhona as an architectural element of Sistan Region, which is often used in closed spaces, on outdoor thermal comfort in the hot and dry climate of Sistan during the summers of 2019 and 2020 with the aim of improving the unfavorable climatic conditions of the region via building on a technique devised by the residents of Sistan. To this end, a kharkhona was designed, built and evaluated in an open urban space. Physiological equivalent temperature index, which has been shown to be highly associated with the sensation of thermal comfort, was used as the indicator for evaluation of outdoor thermal condition. The findings showed that kharkhona can reduce the PET index by 9.34 °C in the space inside kharkhona compared to the environment outside the construct and moderate the “hot” and “very hot” heat sensation of the space outside kharkhona to “warm” and “slightly warm” in the inner space of the construct. Kharkhona can be used as a reference model for designing natural ventilation and is a viable strategy for modification of outdoor thermal comfort since it can provide better comfort conditions than vegetation.
Article
How to utilize the shadows of buildings and greening to jointly improve the thermal cycle of the commercial pedestrian streets in hot and humid areas in southern China is a problem that needs to be discussed. This paper put forward related concepts of the invalid shadow area, valid shadow area, and thermal regulation within valid shaded areas, and designed a model for green planting of commercial pedestrian streets. By learning from relevant standards like ISO7243 and GB/T17244-1998, the paper used methods to measure the WBGT index, and selected two streets of different orientations in Qilou district in Haikou to measure changes in the WBGT index with and without solar radiation. The measurement results provided data for us to determine the time and scope of appearance of the valid shadow area, and thus define the planting area of commercial pedestrian streets Last, this paper conducted simulation analysis on the planting area using Envi-met4. The results indicated that the WBGT index of streets with plants was lower than that of streets without plants (by 1.49℃), and thus plants could provide relief in overheated commercial pedestrian streets.
Article
One fifth of the electricity consumption of Swiss buildings is due to electric lighting. Integrated control of sun shading and artificial lighting can mitigate this demand while maintaining user comfort. However, the drawback of existing building control approaches is that they do not consider one of the main aspects of human-centric lighting: visual comfort. An ‘on-the-fly’ measurement of a visual comfort index, Daylight Glare Probability (DGP), by a novel High Dynamic Range (HDR) vision sensor was introduced into the building control system optimizing the sun shadings position and electric lighting status. As the first approach, this novel solution was tested during a short-term experiment for 15 afternoons at the LESO solar experimental building. The long-term effect of such novel system was evaluated during an eight-month data monitoring campaign. This experiment was carried out in the same building in order to study the ability of a novel control approach to maintain optimal visual and thermal comfort conditions while reducing the energy performance gap of a room as well as its electric lighting demand. The experimental results showed that the advanced controller mitigated the performance gap during the heating season by 72% with regard to a simulated scenario where a standard occupant manually controls the sun shadings and electric lightings; and by 19% with respect to an experimented scenario with best-practice integrated automated shading and lighting system. This system reduced backup heating demand leading to lower CO2 gas emissions. At the same time, visual comfort constraints regarding DGP and workplane horizontal illuminance were respected for 88.1% of work hours.
Thesis
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The world is changing. Temperatures are rising and becoming extreme and unpredictable. Technologies becoming smarter. Computers are playing an increasingly important role in every aspect of our lives. Architecture is no exception, every day the introduction of new technologies helps professionals (architects and urban planning designers) to solve our problems and ease our life. This research aims to explore the possibilities and limits of parametric design as a tool to optimize thermal comfort in urban areas. We made several experiments with the visual programming software grasshopper (Plugin of the CAD software Rhinoceros). We chose Bou Saâda city, characterized by a semi-arid climate and located 245 km south of the Algerian capital, Algiers. Through our readings, we found that urban morphology and vegetation have a considerable impact on urban microclimate. In this work, we have only explored, urban form part. We wrote several algorithms exploring different aspects of urban design and comfort each time. Because comfort is subjective, then we explored different approaches to quantify this sensation. We concluded that the Universal thermal comfort Index (UTCI) is the most accurate index, because it gives the real sensation of temperature. Therefore, we chosen solar radiation as an evaluation parameter because it is more significant related to outdoor thermal comfort and needs less calculation. Secondly, this research aims to define the generation and automation of the building form (Length, width, height, of the blocks and street width) in order to ensure a suitable urban thermal regulation with the appropriate urban building grid.The automation of form generation is the third pillar of our work because we wanted to explore the power of performance-guided form finding through computation. Through our experiments, we found that the integration of the finding results in the urban design workflow has a major impact on urban thermal regulation of newly designed urban areas. The proposed methodology provides an exploration and investigation platform for architects and urban designers. Keyword: Parametric design, Thermal comfort, urban thermal regulation, Form finding, Performative design, evolutionary design.
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The psychometric tool known as the thermal sensation scale has been extensively used in outdoor thermal comfort research. However, this one-dimensional descriptive scale was originally developed for indoor assessments and therefore has certain shortcomings in outdoor settings. The scale contains no affective information such as pleasure and it overlooks the dynamic wind and solar radiation fluxes outdoors. Accordingly, this study develops a six-dimensional semantic framework for outdoor thermal comfort assessments comprising four descriptive - ‘thermal sensation’, ‘humidity’, ‘wind’ and ‘solar radiation,’ plus two affective - ‘thermal pleasure’ and ‘thermal intensity’ dimensions. In Phase 1 an online questionnaire recruited 135 native English-speakers to place 76 climatic adjectives into this six-dimensional semantic space. Phase 2 launched a field study with another 22 subjects locating real-time outdoor thermal experiences in the same semantic space. They were then asked to select from a subset of the 76 climatic adjectives those that best described their right here-right-now thermal experience. Validation was then performed by comparing coordinates of the 31 most frequently chosen adjectives in Phase 2 with those assigned to them in Phase 1. Good correlations (R² > 0.65) of adjectives' coordinates between the two research phases indicate consistency regarding which adjectives best describe specific scenarios, regardless of seasons, locations, or current exposures. The results emphasise that the thermal sensation scale inadequately characterises outdoor thermal comfort experiences. This study initiates the transition of biometeorological comfort research from crude unidimensional descriptive thermal sensation scale, towards a more nuanced, multi-dimensional descriptions of subjective thermal state.
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Global climate is changing as a result of anthropogenic warming, leading to higher daily excursions of temperature in cities. Such elevated temperatures have great implications on human thermal comfort and heat stress, which should be closely monitored. Current methods for heat exposure assessments (surveys, microclimate measurements, and laboratory experiments), however, present several limitations: measurements are scattered in time and space and data gathered on outdoor thermal stress and comfort often does not include physiological and behavioral parameters. To address these shortcomings, Project Coolbit aims to introduce a human-centric approach to thermal comfort assessments. In this study, we propose and evaluate the use of wrist-mounted wearable devices to monitor environmental and physiological responses that span a wide range of spatial and temporal distributions. We introduce an integrated wearable weather station that records a) microclimate parameters (such as air temperature and humidity), b) physiological parameters (heart rate, skin temperature and humidity), and c) subjective feedback. The feasibility of this methodology to assess thermal comfort and heat stress is then evaluated using two sets of experiments: controlled-environment physiological data collection, and outdoor environmental data collection. We find that using the data obtained through the wrist-mounted wearables, core temperature can be predicted non-invasively with 95 percent of target attainment (PTA) within 0.27C. Additionally, a direct connection between the air temperature at the wrist (Ta,w) and the perceived activity level (PAV) of individuals was drawn. We observe that with increased Ta,w, the desire for physical activity is significantly reduced, reaching "Transition only" PAV level at 36C. These assessments reveal that the wearable methodology provides a comprehensive and accurate representation of human heat exposure, which can be extended in real-time to cover a large spatial distribution in a given city and quantify the impact of heat exposure on human life.
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Thermal comfort indices are vital tools when assessing outdoor thermal comfort in hot and arid environments. Selecting a representative thermal comfort index for outdoor environments is challenging. This paper presents a comparative study of the suitability of seven different thermal comfort indices, namely PMV, discomfort index, cooling power index, Humidex, WBGT, SET, and UTCI in assessing outdoor thermal comfort. The thermal comfort indices were compared to the thermal sensation vote (TSV) obtained from a thermal comfort questionnaire of spectators seated in a semi-open air-conditioned stadium. Seated in six different zones, a total of 532 spectators participated in an online questionnaire. The results of the survey indicated high levels of climate acceptability, with small variations among the stadium zones and between genders. Almost 40% of the spectators reported feeling ‘’cool’’, while 28% of the spectators were feeling ‘’slightly cool’’ and 21% reported a ‘’neutral’’ thermal perception. Hence, CFD simulations were used to predict the values of the seven thermal comfort indices. The thermal comfort indices values, obtained from the CFD simulations, were compared to their counterparts obtained from the questionnaire. The WBGT index showed good agreement to the actual questionnaire data with an average difference of 8.8%. The other six indices yielded an average range of difference of (15%-46%). The WBGT index deemed the most suitable to assess outdoor thermal comfort for hot and arid regions, followed by the UTCI and the SET indices, with average differences of 14% and 15%, respectively. The CPI index deemed not suitable for hot and arid regions compared to other indices.
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The configuration of urban street-canyons, especially the ratio of the height of the buildings to the street width (H/W) and length to width (L/W), plays an essential role in directing and dispersion of wind flow and consequently affects changes in air temperature and urban heat islands (UHI). Despite many studies examining the aspect ratio of street-canyons, failure to follow these ratios from a specific order and organization and the lack of an optimal range for urban design is a gap seen in these studies. In addition, if the H/W exceeds a certain range, the results will change significantly and sometimes in reverse. Therefore, this paper simulates a residential town using CFD calculations in ANSYS-CFX 18. In two different scenarios (each scenario has four modes), wind flow and temperature changes were evaluated to find the optimal value of H/W and L/W. The analysis of changes in the three factors of wind velocity, temperature, and pressure show that the ratios H/W =1 and L/W=2 are the most suitable conditions for temperature reduction and UHI control. In addition, a sensitivity analysis confirms the generalizability of the obtained ratios to other fields with different temperature conditions and wind speeds.
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This work implements parametric tools to optimize the environmental design of urban adaptive shadings through multiobjective evolutionary algorithms that look for solutions of dynamic (time-changing) structures used in open public spaces. The proposal is located in Malecon Cancun Tajamar in the southeast part of Mexico, and the main objective is to enhance the thermal comfort of users as well as to become part of the social dynamics of the place reinforcing identity through appropriation. The proposed workflow includes four steps: (1) geometric modelling by parametric modelling tools; (2) simulation of environmental parameters by using BPS tools; (3) shape optimization by using an evolutionary algorithm; and (4) environmental verification of the results. The Universal Thermal Climate Index (UTCI) was used to assess the outdoor thermal comfort derived from the dynamic shadings. The results showed a significant improvement in the thermal comfort with absolute UTCI differences of 3.9, 7.4, and 3.1 �C at 8, 12, and 16 h, respectively, during the summer; and absolute differences of 1.4, 3.5, and 2 �C at 8, 12, and 16 h, respectively, during the winter. The proposed workflow can help to guide the early design process of dynamic shadings by finding optimal solutions that enhance outdoor thermal comfort.
Conference Paper
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The present work deals with the determination of thermal comfort maps in large enclosures. Currently no specific approach is proposed to this end as building simulation relies on a nodal approach, where the computed scalar values (e.g. temperature, humidity, solar flux) are homogeneously distributed in zones whatever their size. We present here a method allowing for the calculation of a spatial distribution of thermal comfort, enhancing the classical approach by a precise determination of indoor solar fluxes and isothermal air velocities.
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We consider the problem of statistically modelling the thermal perception as a function of Outdoor Thermal Comfort (OTC) via partitioning based regression models. Such models have been widely used, but may not be fully understood and theoretically justified by practitioners. To close the gaps between statistical theory and applications of OTC analysis, we first provide a formal mathematical representation of the widely used partitioning based regression models. We provide the interpretation of those models from a statistical point of view, and make the modelling assumptions explicit and clear. We then show that these partitioning based regression models can be understood as a semi-parametric regression model, known as Regressogram. We analyze the theoretical properties of the Regressogram and develop a simple algorithm for choosing the optimal number of bins, which is based on a combination of goodness-of-fit test and cross-validation methods. We then derive various quantities which are of importance for climate-informed urban design, including the predictive distribution and a new statistical measure for thermal acceptability, called the Probabilistic Acceptability Criterion (PAC). Overall, the proposed framework is designed to help climate practitioners gain better understanding of OTC regression methods and place the practices currently used on a statistically rigorous footing.
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The article presents an innovative procedure that allows for an analysis of the influence of the shape and mutual arrangement of external building partitions on the amount of the direct solar irradiation incident on these partitions during a heating season. The conducted analysis related interdisciplinary issues in the field of solar radiation, unconventional forms of buildings and artificial neural networks. The developed algorithm made it possible to obtain a relationship between the general building form and the amount of their radiation falling on the facade walls and roof of the examined building type. The developed artificial network allows the above irradiation to be calculated during the changes in the geometrical characteristics of the utilized type of buildings and design of effective building forms and rational arrangements of their external solar partitions. The satellite data and online tools published on the website of the European Commission are used. The practicable ranges of the relative changes in the amount of the incident direct irradiation and the corresponding values of the independent variables defining the considered building forms are given, which is an important hint for the application of the obtained results in the design and further research works on more complex relationships.
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In this paper, the fundamentals of a 3D nested construction method for 3D-printing stackable tower-like structures are explained, taking into consideration the transportation, storage, assembly, and even disassembly of building components. The proposed method is called “PRINT in PRINT.” This paper also documents the authors’ experience of and findings from designing and printing a column erected out of a series of 3D printed components in a short stack. Employing the design principles of 3D printing in a nested fashion, the authors showcase the main parameters involved in dividing the column’s global geometry into stackable components. By converting formal, technical, and material restrictions of a robotic-assisted 3D printing process into geometric constraints, the paper describes how the column components are divided, namely that one component shapes the adjacent one.
Thesis
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Focusing on the urban block scale in hot climates, this dissertation offers new insights into the nexus between urban form and environmental performance. It introduces and explores a new set of harmonized workflows which by capitalizing on the benefits of a parametric environment open new possibilities in the pursuit of a sustainable urban form - going beyond energy considerations towards environmental quality and urban livability. Beyond the ability to reproduce these workflows for environmentally driven urban design in practice, this dissertation highlights current limitations and future outlooks which pave the way for further exploration.
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Proceedings of the 15th International Congress of Biometeorology and International Conference on Urban Climatology, edited by R. de Dear and J. Potter (Macquarie University; Sydney) (ISBN 1 86408 5436). pp.ICB9.4.1-6.
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Outdoor spaces play important roles in daily lives, and the use of these spaces is determined largely by outdoor thermal comfort. Few studies have been conducted on outdoor thermal comfort in northern China. Using microclimatic monitoring and subject interviews at a park in Tianjin, China, this investigation studied outdoor thermal comfort under different climate conditions. Although outdoor thermal environment varied greatly with air temperature from -5.0 to 34.5oC, 83.3% of respondents consider it “acceptable”. Preferences in solar radiation, wind speed, and relative humidity were related to air temperature. The higher the air temperature was, the higher the wind speed and the lower the solar radiation and relative humidity desired by the occupants, and vice versa. The data were also used to evaluate three indices. The Universal Thermal Climate Index (UTCI) satisfactorily predicted outdoor thermal comfort, while the Predicted Mean Vote (PMV) overestimated it. The neutral Physiological Equivalent Temperature (PET) range found in this study was 11-24oC, which was lower than the ranges in Europe and Taiwan. Our study indicated that residents of Tianjin were more adapted to cold environment.
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Thermal comfort is a subjective psychological perception of people based also on physiological thermoregulation mechanisms when the human body is exposed to a combination of various environmental factors including air temperature, air humidity, wind speed, and radiation conditions. Due to the importance of gender in the issue of outdoor thermal comfort, this study compared and examined the thermal comfort-related differences between male and female subjects using previous data from Taiwanese questionnaire survey. Compared with males, the results indicated that females in Taiwan are less tolerant to hot conditions and intensely protect themselves from sun exposure. Our analytical results are inconsistent with the findings of previous physiological studies concerning thermal comfort indicating that females have superior thermal physiological tolerance than males. On the contrary, our findings can be interpreted on psychological level. Environmental behavioral learning theory was adopted in this study to elucidate this observed contradiction between the autonomic thermal physiological and psychological-behavioral aspects. Women might desire for a light skin tone through social learning processes, such as observation and education, which is subsequently reflected in their psychological perceptions (fears of heat and sun exposure) and behavioral adjustments (carrying umbrellas or searching for shade). Hence, these unique psychological and behavioral phenomena cannot be directly explained by autonomic physiological thermoregulation mechanisms. The findings of this study serve as a reference for designing spaces that accommodates gender-specific thermal comfort characteristics. Recommendations include providing additional suitable sheltered areas in open areas, such as city squares and parks, to satisfy the thermal comfort needs of females.
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Optimization of building energy use in an urban area requires understanding of the complex interaction between urban morphology, materials, and climate, which can have unanticipated effects on urban microclimates and building energy use. Reflective pavements reduce urban air temperatures and have been proposed as a mitigation measure for urban heat islands. However, the increased solar reflectivity also transports more solar radiation into (through windows) and onto adjacent buildings possibly increasing building energy use. The effect of albedo changes in the urban canopy floor surface on building thermal loads is investigated using the Temperature of Urban Facets Indoor-Outdoor Building Energy Simulator (TUF-IOBES). A case study for a four storey office building with 1820 m2 floor area and 47% window to wall ratio in Phoenix, Arizona was conducted. Increasing pavement solar reflectivity from 0.1 to 0.5 increased annual cooling loads up to 11% (33.1 kWh m−2). The impacts on annual heating loads and canopy air temperatures were small. The confounding impacts of canopy aspect ratio, building insulation conditions reflective of building age, and window type and size were also quantified. Policymakers should carefully weigh the benefits and local energy use implications of reflective pavements for each site to ensure their optimal application.
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From extensive outdoor comfort campaigns, preliminary outdoor comfort ranges have been defined for the local population of Glasgow, UK, in terms of two thermal indices: ‘Temperature Humidity Sun Wind’ (THSW) and ‘Physiological Equivalent Temperature’ (PET). A series of measurements and surveys was carried out from winter through summer 2011 during 19 monitoring campaigns. For data collection, a Davis Vantage Pro2 weather station was used, which was equipped with temperature and humidity sensors, cup anemometer with wind vane, silicon pyranometer and globe thermometer. From concurrent measurements using two weather stations, one located close to the city core and another located at a rural setting, approximately at a 15-km distance from the urban area of Glasgow, comparisons were made with regard to thermal comfort levels and to urban–rural temperature differences for different periods of the year. It was found that the two selected thermal indices (THSW and PET) closely correlate to the actual thermal sensation of respondents. Moreover, results show that the urban site will have fewer days of cold discomfort, more days of ‘neutral’ thermal sensation and slightly higher warm discomfort. The most frequent urban heat island intensity was found to be around 3° C, whereas the fraction of cooling to heating degree-hours for a T base of 65 °F was approximately 1/12th.
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The present paper deals with the dependence of outdoor thermal comfort on the design of an urban street. The effects of the street vertical profile, including asymmetrical canyon shapes, the use of galleries and further shading devices on the façades, arranged in various orientations are assessed. The study is conducted by means of numerical modelling by using the three-dimensional microclimate model ENVI-met 3.0 which prognosticates the microclimatic changes within urban environments. Thermal comfort is evaluated for the daytime hours across the canyon in high spatial resolution and by means of the physiologically equivalent temperature PET.The results revealed that all design aspects investigated have a moderate impact on the air temperature and a strong effect on the heat gained by a human body and hence on the resulting thermal sensation. The larger the openness to the sky of the canyon, the higher the heat stress. For canyons with a smaller sky view, the orientation is also decisive: E–W canyons are the most stressful and deviating from this orientation ameliorates the thermal conditions. Basically, galleries and further shading through overhanging façades or vegetation enable a sensitive decrease of the period of time and of the area of thermal discomfort. Yet, this efficiency varies with the orientation and the vertical proportions of the canyon. Therefore, if appropriately combined, all investigated design elements can effectively mitigate heat stress in the summer and promote thermal comfort.
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Reconstructed daily mean sea level pressure patterns of the North Atlantic–European region are clas-sified for the period 1850 to 2003 to explore long-term changes of the atmospheric circulation and its impact on long-term temperature variability in the central European region. Commonly used k-means clustering algorithms resulted in classifications of low quality because of methodological deficiencies leading to local optima by chance for complex datasets. In contrast, a newly implemented clustering scheme combining the concepts of simulated annealing and diversified randomization (SANDRA) is able to reduce substantially the influence of chance in the cluster assignment, leading to partitions that are noticeably nearer to the global optimum and more stable. The differences between conventional cluster analysis and the SANDRA scheme are significant for subsequent analyses of single clusters—in particular, for trend analysis. Conven-tional indices used to determine the appropriate number of clusters failed to provide clear guidance, indicating that no distinct separation between clusters of circulation types exists in the dataset. Therefore, the number of clusters is determined by an external indicator, the so-called dominance criteria for t-mode principal component analysis. Nevertheless, the resulting partitions are stable for certain numbers of clus-ters and provide meaningful and reproducible clusters. The resulting types of pressure patterns reveal pronounced long-term variability and various significant trends of the time series of seasonal cluster fre-quency. Tentative estimations of central European temperature changes based solely on seasonal cluster frequencies can explain between 33.9% (summer) and 59.0% (winter) of temperature variance on the seasonal time scale. However, the signs of long-term changes in temperature are correctly reproduced even on multidecadal–centennial time scales. Moreover, linear warming trends are reproduced, implying from one-third up to one-half of the observed temperature increase between 1851/52 and 2003 (except for summer, but with significant trends for spring and autumn), indicating that changes in daily circulation patterns contribute to the observed overall long-term warming in the central European region.
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The effects of vegetation on human thermal stress in a hot-arid region were tested in two semi-enclosed urban spaces with various combinations of mature trees, grass, overhead shading mesh and paving. The index of thermal stress was calculated hourly from measured meteorological data in the studied sites to evaluate thermal comfort in the different spaces based on radiative and convective pedestrian–environment energy exchanges and sweat efficiency, and expressed on a thermal sensation scale ranging from ‘comfortable’ to ‘very hot’. The efficiency of water use in providing improved comfort was gauged for each of the vegetative landscaping treatments by comparing the total evapotranspiration with the reduction in thermal stress, both expressed in terms of their values in equivalent energy. While conditions in a paved, unshaded courtyard were found to be uncomfortable throughout the daytime hours (with half of these hours defined by severe discomfort), each of the landscape treatments made a clear contribution to improved thermal comfort. With shading, either by trees or mesh, discomfort was reduced in duration by over half and limited in maximum severity when the shading was placed above paving. When combined with grass, both shading mechanisms yielded comfortable conditions at all hours. In both cases, the effect of trees was more pronounced than that of the mesh, but by a small margin. With unshaded grass, ‘hot’ conditions in the courtyard were restricted to a short period in mid-afternoon, a considerable improvement over unshaded paving, attributable mainly to the lower radiant surface temperatures. Copyright © 2010 Royal Meteorological Society
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The origin and development of the adaptive approach to thermal comfort is explained. A number of recent developments in the application of the theory are considered and the origin of the differences between adaptive thermal comfort and the ‘rational’ indices is explored. The application of the adaptive approach to thermal comfort standards is considered and recommendations made as to the best comfort temperature, the range of comfortable environments and the maximum rate of change of indoor temperature. The application of criteria of sustainability to thermal standards for buildings is also considered.
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With the rise in urban air temperature, heat stress and thermal discomfort are challenging the livability of urban environments. To respond to this concern, we employ numerical modeling to evaluate the spatial and temporal variabilities of thermal comfort and introduce a simulation tool: outdoor thermal comfort in 3D (OTC3D). The model builds upon the work by Nazarian et al., 2017, and is a) extended to evaluate realistic urban configurations, b) validated against measurements, c) enabled to intake a wide resolution range of microclimate parameters (modular approach), and d) made available on an open-source platform. Using OTC3D, we evaluated outdoor thermal comfort (OTC) in two urban configurations: idealized and realistic. In the realistic configuration, we demonstrate the functionality of the model in presenting the variability of OTC in an urban neighborhood. Using the idealized configuration, on the other hand, we performed sensitivity studies regarding the effects of urban density and realistic surface heating. First, we observed that thermal comfort changes non-monotonically with urban density, as the ensuing change in wind speed and radiation patterns have counteracting effects on thermal comfort. Accordingly, to achieve the desired thermal comfort in hot climates, strategies to enhance urban ventilation are favored in higher densities, while strategies to minimize radiation are needed for lower urban packing densities. Furthermore, we observed that realistic distribution of surface temperature is critical when urban density is high (e.g. λp = 0.44). Therefore, approximations of surface temperature found in existing thermal comfort models are not suited for high-density urban areas. This further motivates the modular approach to improve the accuracy of thermal comfort analysis.
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Providing good environmental conditions for educational buildings has always been critical because of the negative influence of thermal and visual discomfort on students’ learning and performance. Unsatisfactory conditions mostly caused by overheating and glare due to the presence of direct solar radiation, could be compensated by appropriate window configurations. Since occupants are obligated to sit in defined positions in classrooms, spatial analysis of the thermal and visual field are necessary in addition to temporal evaluations. This paper applies both spatio-temporal thermal and visual comfort metrics, to assess the effect of window design on comfort by dynamic simulations in a south and north faced classroom model in Tehran’s Climatic condition. The SolarCal method, which considers the direct effect of solar radiation on occupants, validated by field measurements, is used to assess local thermal comfort. A solution space, presented in graphs has been defined for each orientation by the defined comfort targets. These graphs could be used to select the optimum glazing properties based on the desired window wall ratio. The defined solution areas are larger in the south orientation and could be extended by considering shadings. Results show that low U-values and low Solar Heat Gain Coefficient (SHGC) are needed in both north and south faced classrooms to decrease the overheating risk. Also the use of double glazing units is not always required or the most favorable option for all window sizes. Based on the results the most effective factors for window design in regard to spatio-temporal thermal comfort are Window Wall Ratio (WWR), glazing SHGC and window shadings, orientation, and window U-value respectively. However, WWR, orientation, and glazing Visual Transmittance (VT) and shadings have almost equal effect on spatio-temporal visual comfort.
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In tropical regions, semi-outdoor spaces are very common in commercial buildings or residential buildings. In this study, we conducted questionnaire survey in several places which could be regarded as semi-outdoor spaces. The questionnaire survey covered both the objective measurements and the subjective evaluations, which were conducted simultaneously. Based on the data from the field survey, simple relationships between the air temperature and thermal comfort votes (TCV) at each air velocity and RH bin were established using the linear regression technique. A ventilation comfort chart was developed to illustrate the interdependent relationship amongst the three environmental parameters (air temperature. RH and air velocity) in affecting thermal comfort of semi-outdoor spaces in the tropics. The ventilation comfort chart can provide useful reference to designer in terms of achieving thermal comfort in semi-outdoor spaces.
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The aim of this paper is to review the literature on human thermal comfort in the built environment. First an overview about the subject area is presented. This is followed by a review of papers published in the last 10 years that examine the various sub-areas of research related to human thermal comfort. Some remarkable works about both the Fanger's and adaptive thermal comfort models are also discussed. This review does not contain simulation works and/or experimental studies without subjective results of people. As a result of the literature review, 466 articles were classified and grouped to form the body of this article. The article examines standards, indoor experiments in controlled environments (climate chamber) and semi-controlled environments, indoor field studies in educational, office, residential and other building types, productivity, human physiological models, outdoor and semi-outdoor field studies. Several research topics are also addressed involving naturally ventilated, air-conditioned and mixed-mode buildings, personalized conditioning systems and the influence of personal (age, weight, gender, thermal history) and environmental (controls, layout, air movement, humidity, among others) variables on thermal comfort.
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This historical review of 20 studies since the 1960s examines the influence of urban development on the thermal environment in Singapore, a fast growing tropical island city-state. Past observations are critically assessed with regard to experimental controls and station metadata. Given the availability of historical climate and developmental data spanning almost 50 years, changes in urban heat island (UHI) intensity and spatial coverage can be traced temporally. Rapid urban expansion in Singapore is clearly reflected in spatially and temporally changing air and surface temperature patterns. The nocturnal canopy-layer UHI intensity – measured as the difference between the commercial urban core and undeveloped areas close to primary or secondary rainforests for example – doubled in magnitude between 1965 and 2004. At the same time, the spatial extent of the nocturnal UHI has also expanded with the development of new housing and industrial districts. The influence of the growing city is also reflected in surface temperature. Two satellite images dated 13 years apart demonstrate the encroachment of areas with high surface temperatures into previously cooler areas during daytime corresponding with new public housing estates and low-rise residential areas or facilities being built. The results from our study contribute to the growing body of tropical heat island research. They provide baseline data for future research and urban development in the Singapore context and, more generally, offer important cues for urban planners to make tropical cities more sustainable.
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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.
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Using the latest HadGHCND daily temperature dataset, global trends in observed summertime heatwaves and annually calculated warm spells for 1950-2011 are analysed via a multi-index, multi-aspect framework. Three indices that separately focus on maximum temperature (TX90pct), minimum temperature (TN90pct) and average temperature (EHF) were studied with respect to five characteristics of event intensity, frequency and duration. Despite which index is employed, increases in heatwave/warm spell intensity, frequency and duration are found. Furthermore, TX90pct and TN90pct trends are larger and exhibit more significance for warm spells, implying that non-summer events are driving annual trends over some regions. Larger increases in TN90pct aspects relative to EHF and TX90pct are also observed. While qualitative information on event trends is similar across the indices, quantitative values vary. This result highlights the importance of employing the most appropriate index when assessing the impact of sustained extreme temperature events.
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A thermal comfort study has been carried out in outdoor urban spaces in Singapore. The field study was carried out from August 2010 to May 2011. There were 2059 respondents from 13 different outdoor spaces participated in this study and 2036 effective questionnaire responses were collected. Thermal comfort perceptions and preferences were analyzed in this study. The neutral operative temperature occurred at 28.7 °C and preferred temperature was found to be 26.5 °C. Thermal acceptability analysis shows the acceptable operative temperature range was 26.3–31.7 °C in outdoor urban spaces in Singapore. Correlation analysis indicates that sun sensation/solar radiation has the most significant influence on human thermal sensation in outdoor spaces. This study also explores the impact of thermal adaptation on human thermal sensation in outdoor spaces, which could be useful for future researchers. Comparative analysis shows that people may expect a higher temperature in outdoor conditions than in semi-outdoor or indoor conditions in Singapore, suggesting that people in outdoor conditions could be more tolerant with the heat stress than people in indoor conditions in tropical climate.
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The goal of this research is to bridge the gap between numerical studies and field measurements on thermal environment of a real urban street and to present information on the effects of urban vegetation suitable for use by designers and planners. Outdoor measurements were conducted at a scale model site consisting of an array of concrete cubes each 1.5 m high. Eight urban street units with various vegetation conditions were reproduced to examine the quantitative effects of vegetation along the sidewalk and in median strips on the thermal environment in summer. The results can be summarized as follows. The presence of four sidewalk trees reduces the wind speed inside the canopy by up to 51%. Trees along the sidewalk also decrease the globe temperature; the reduction is attributed mainly to the decrease in radiation flux resulting from the shade they cast. Moreover, thermal mitigation due to vegetation persists even when an area is shaded. In contrast, the mitigating effect of a vegetated median strip is not remarkable. A sidewalk facing a southwestern wall exhibited the most significant thermal mitigation.
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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.
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The increase in air temperature produced by urbanization, a phenomenon known as the urban heat island (UHI) effect, is often neglected in current building energy simulation practices. The UHI effect can have an impact on the energy consumption of buildings, especially those with low internal heat gains or with an inherent close interaction with the outdoor environment (e.g. naturally-ventilated buildings). This paper presents an urban weather generator (UWG) to calculate air temperatures inside urban canyons from measurements at an operational weather station located in an open area outside a city. The model can be used alone or integrated into existing programmes in order to account for the UHI effect in building energy simulations. The UWG is evaluated against field data from Basel (Switzerland) and Toulouse (France). The error of UWG predictions stays within the range of air temperature variability observed in different locations of the same urban area.
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Cited By (since 1996):1, Export Date: 13 June 2013, Source: Scopus, CODEN: ENEBD, :doi 10.1016/j.enbuild.2012.06.015, Language of Original Document: English, Correspondence Address: Carlucci, S.; Energy Department, End-use Efficiency Research Group, Politecnico di Milano, Via Lambrischini 4, 20156, Milano, Italy; email: salvatore.carlucci@polimi.it, References: Kalkstein, L.S., Valimont, K.M., An evaluation of summer discomfort in the United States using a relative climatological index (1986) Bulletin of the American Meteorological Society, 7, pp. 842-848;
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A new database of weather and circulation type catalogs is presented comprising 17 automated classification methods and five subjective classifications. It was compiled within COST Action 733 “Harmonisation and Applications of Weather Type Classifications for European regions” in order to evaluate different methods for weather and circulation type classification. This paper gives a technical description of the included methods using a new conceptual categorization for classification methods reflecting the strategy for the definition of types. Methods using predefined types include manual and threshold based classifications while methods producing types derived from the input data include those based on eigenvector techniques, leader algorithms and optimization algorithms. In order to allow direct comparisons between the methods, the circulation input data and the methods’ configuration were harmonized for producing a subset of standard catalogs of the automated methods. The harmonization includes the data source, the climatic parameters used, the classification period as well as the spatial domain and the number of types. Frequency based characteristics of the resulting catalogs are presented, including variation of class sizes, persistence, seasonal and inter-annual variability as well as trends of the annual frequency time series. The methodological concept of the classifications is partly reflected by these properties of the resulting catalogs. It is shown that the types of subjective classifications compared to automated methods show higher persistence, inter-annual variation and long-term trends. Among the automated classifications optimization methods show a tendency for longer persistence and higher seasonal variation. However, it is also concluded that the distance metric used and the data preprocessing play at least an equally important role for the properties of the resulting classification compared to the algorithm used for type definition and assignment.