No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Outdoor thermal comfort autonomy: Performance metrics for climate-conscious urban design
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.
... 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. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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). ...
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.
... 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]. ...
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.
... 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). ...
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.
... Numerous factors are involved in intensifying or reducing the effect of urban heat islands in metropolitan areas, especially around high-rise buildings. And how these factors combine can help maintain or remove heat generated by human activities and vehicles and other factors that cause pollution and heat (Adelia et al., 2019;Djukic et al., 2016;Futcher et al., 2017;Gago et al., 2013;Giridharan & Emmanuel, 2018;Guo et al., 2019;Kotharkar et al., 2018;Nakata-Osaki et al., 2018;Nazarian et al., 2019;Qaid et al., 2016;Ramakreshnan et al., 2018;Wu & Han, 2019;Yang et al., 2019). One of the most effective factors is the morphology and the composition and arrangement of the city components (Adamek et al., 2017;Chew & Norford, 2018;Hofman et al., 2019;Zhang et al., 2017), Which is discussed and evaluated in this article. ...
... Different ratios of street canyons from shallow to deep have been used in research to assess factors affecting changes in temperature, pollution concentration, or wind velocity. The results of these studies are related to different conditions and provide useful information about how heat islands are formed in the street canyons and strategies to reduce them (Allegrini, 2018;Aristodemou et al., 2018;Chew & Norford, 2018;Cui et al., 2019;Gagliano et al., 2017;Guo et al., 2019;Hofman et al., 2019;Kim et al., 2019;Lin et al., 2020;Marucci & Carpentieri, 2019;Nakata-Osaki et al., 2018;Nazarian et al., 2019;Perini et al., 2017;Qaid et al., 2016;Rajagopalan et al., 2014;Reiminger et al., 2019;Tsichritzis et al., 2019;Wen et al., 2018;Wu & Han, 2019;Yang et al., 2019;Zhang et al., 2017;Zhang et al., 2019). But these ratios cannot be used as optimal values for all research and urban design planning. ...
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.
... 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. ...
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.
... The focus here is on the range of thermal exposure, such that we identify the cool and hot spots within the grid cell without having to resolve the entire spatial distribution. We argue that this represents the most crucial information for heat management and urban spots are experiencing extreme heat stress but the cool spots are at slight heat stress, pedestrians have the opportunity, and autonomy, to seek shade and thermal respite (i.e., spatial autonomy as described in Nazarian et al. (2019) ). Conversely, if the conditions in the cool spot are already in extreme heat stress, this can be used to inform urban design interventions or heat advisories to vulnerable populations to avoid being outside at that place and time. ...
Urban overheating, and its ongoing exacerbation due to global warming and urban development, leads to increased exposure to urban heat and increased thermal discomfort and heat stress. To quantify thermal stress, specific indices have been proposed that depend on air temperature, mean radiant temperature (MRT), wind speed, and relative humidity. While temperature and humidity vary on scales of hundreds of meters, MRT and wind speed are strongly affected by individual buildings and trees, and vary at the meter scale. Therefore, most numerical thermal comfort studies apply micro-scale models to limited spatial domains (commonly representing urban neighborhoods with building blocks) with resolutions on the order of 1 m and a few hours of simulation. This prevents the analysis of the impact of city-scale adaptation/mitigation strategies on thermal stress and comfort. To solve this problem, we develop a methodology to estimate thermal stress indicators and their subgrid variability in mesoscale models – here applied to the multilayer urban canopy parametrization BEP-BEM within the WRF model. The new scheme (consisting of three main steps) can readily assess intra-neighborhood scale heat stress distributions across whole cities and for time scales of minutes to years. The first key component of the approach is the estimation of MRT in several locations within streets for different street orientations. Second, mean wind speed, and its subgrid variability, are parameterized as a function of the local urban morphology based on relations derived from a set of microscale LES and RANS simulations across a wide range of realistic and idealized urban morphologies. Lastly, we compute the distributions of two thermal stress indices for each grid square combining all the subgrid values of MRT, wind speed, air temperature, and absolute humidity. From these distributions, we quantify the high and low tails of the heat stress distribution in each grid square across the city, representing the thermal diversity experienced in street canyons. In this contribution, we present the core methodology as well as simulation results for Madrid (Spain), which illustrate strong differences between heat stress indices and common heat metrics like air or surface temperature, both across the city and over the diurnal cycle.
... P r e p r i n t n o t p e e r r e v i e w e d approaches is comparable [16], hybrid approaches also support the replacement of time and computationally expensive components with surrogate models, faster computation, approximations, or simplifications. Examples include reducing modelling fidelity through discounting lowest contributors to OTC [17], lowering the temporal resolution through weather clustering [28], [29], decreasing the number of simulated wind directions [17], simplifying MRT calculations using surface clustering [30] and replacing wind estimation by surrogate models [31], [32]. A substantial body of research has specifically focussed on the main bottleneck of OTC calculations: ...
... According to the authors, OTCA considers the percentage of time an outdoor space is within the desired thermal comfort range, including periods where the thermal comfort level is below the threshold. It is an extension of Spatial OTCA, defined as the percentage of outdoor space within the desired thermal comfort range at least half of the occupied time (over a year or a prescribed period of use) [44]. ...
Climatic and micro-climatic phenomena such as summer heat waves and Urban Heat Island (UHI) are increasingly endangering the city's livability and safety. The importance of urban features on the UHI effect encourages us to consider the configuration of urban elements to improve cities' sustainability and livability. Most solutions are viable when a city redevelops and new areas are built to focus on aspects such as optimum design and the orientation of building masses and streets, which affect thermal comfort. This research looks beyond outdoor thermal comfort studies using UHI data and geoprocessing techniques in Tallinn, Estonia. This study supposes that designing urban canyons with proper orientation helps to mitigate the UHI effect by maximizing outdoor thermal comfort at the pedestrian level during hot summer days. In addition, optimizing the orientation of buildings makes it possible to create shaded and cooler areas for pedestrians, reducing surface temperature, which may create more comfortable and sustainable urban environments with lower energy demands and reduced heat-related health risks. This research aims to generate valuable insights into how urban environments can be designed and configured to improve sustainability, livability, and outdoor thermal comfort for pedestrians. According to the study results, researchers can identify the most effective interventions to achieve these objectives by leveraging UHI data and geoprocessing techniques and using CFD simulations. This evaluation is beneficial in guiding urban planners and architects in proposing mitigation solutions to enhance thermal comfort in cities and creating suitable conditions for approved thermal comfort levels. Results of the study show that in the location used for the survey, Tallinn, Estonia, the orientation of West-East offers the optimum level of comfort regarding thermal comfort and surface temperature in the urban environment.
... Low-income rehabilitation and resettlement projects tend to overheat due to poor planning of layouts and spatial arrangements (Ali & Patnaik, 2018;Chen et al., 2018;Nazarian N. et al., 2019;Wang et al., 2019). Studies in low-income housing settlements across the country have shown that most occupants are dissatisfied with the thermal environments and the comfort levels achieved in their units. ...
This chapter looks at how low-cost mass housing makes inhabitants more vulnerable to impacts of climate change such as extreme heat. The chapter, therefore, specifically aims to establish an interlinkage between climate change and public health. Rising temperatures due to climate change and urban heat island effects will generally 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. Low-income households in mass housing generally lack agency over their housing situation and have little means to adapt to heat. While buildings constitute their single most important and effective means of protection against heat stress, for most low-income households, design restrictions and the use of cheap building materials strongly limit this protection’s effectiveness.
... Assessing spatially and temporally differentiated TCIs requires care because of the wide range of conditions that people experience moving through urban environments. Metrics for outdoor thermal comfort and thermal exposure, such as outdoor thermal comfort autonomy, can succinctly describe overall conditions and assist in providing micro-to cityscale analysis, which can intelligently inform urban design (Nazarian et al., 2019a). ...
Urban climate models—focused on various scales and perspectives—provide important means to analyze complex physical processes forming urban climates and further quantify the ways climate change and urbanization have resulted, and will result, in local-scale modification of climate in the built environment. This chapter aims to provide an overview of the state-of-the-art in modeling urban and intraurban climate variability at various scales in cities and documenting the interaction with larger-scale climate change impacts. To achieve this objective, we first discuss various modeling techniques that assist us in evaluating urban climate processes at various scales and levels of complexity. Forcing on numerical models, we then discuss how key physical processes (such as vegetation and anthropogenic heat and water wastes) are infused in state-of-the-art modeling techniques across different scales. Lastly, we provide a more in-depth review of modeling approaches applied to simulate various implications of urban and intraurban climate, ranging from thermal exposure to high-impact weather.
... Despite the vast amount of theoretical research available, limited studies were translated into practical actions that resulted in a gap between research and application [ 1 , 2 , 3 ]. Nazarian et al. [4] stated that there are limitations in supporting architects, planners, and decision makers on strategies that cover the performance of outdoor spaces in terms of thermal comfort. Matos Silva and Costa [5] stated that diminishing the gap between theory and practice could inform a better design of outdoor urban environments in times of drastic climate change. ...
The concept of future-proofing cities seeks to minimise environmental impacts by utilising various mitigation and adaptation techniques, specifically by improving urban fabric. Studies on urban forms and parameters have been extensively conducted in hot, arid and humid climates while they have been less investigated in temperate climates. In the UK, the current local urban design guides meet the needs of designers and urban planners, however, they are still considered descriptive and lack in-depth environmental assessment. This study aims to investigate the recommended threshold values in the National Model Design Code against real sites with different urban canyons morphologies to examine their impact on outdoor environmental conditions. The study used quantitative methods by conducting a review study, a survey on UK urban design guides and modelling using simulation via RayMan and IESVE. The study targeted pre-selected sites in Cardiff and Bristol that were identified as zones with urban heat stress. The results showed that the Aspect Ratio and Sky View Factor (SVF) in two cities have significantly impacted outdoor environmental conditions in urban areas subsequently affecting the Physiological Equivalent Temperature (PET). The results showed that the recommended values have a significant impact on the outdoor thermal performance of the pre-selected urban canyons. The findings demonstrated that modifying the width of streets and changing the Aspect Ratio and SVF resulted in achieving a positive impact during summer when both factors have a direct relationship. However, when the Aspect Ratio and SVF have an inverse relationship, the results demonstrated extreme cold stress during winter. Therefore, maintaining a direct relationship between the Aspect Ratio and SVF would help to improve outdoor conditions.
... Existing research has evaluated occupants' comfort in outdoor spaces using different thermal indices, such as the Wet-Bulb Globe Temperature (WBGT) [7], Universal Thermal Climate Index (UTCI) [7,70,71], Standard Effective Temperature (SET) [71,72], Predicted Mean Vote (PMV) [71], Physiological Equivalent Temperature (PET) [71,73], and others [74][75][76][77][78][79][80][81]. Generally, in outdoor thermal spaces, thermal comfort is influenced by the dominant microclimate variables, such as wind velocity, etc. [69,75]. ...
This study assesses the impacts of urban configurations on thermal perceptions in Flat Bandar Tasik Selatan (FBTS) and Surya Magna (SM) in Kuala Lumpur, Malaysia. It aims to understand the impacts of urban configurations on thermal perceptions in outdoor spaces. The study addresses the following research questions: (1) Do urban configurations influence outdoor comfort? (2) Do urban configurations also have significant impacts on thermal perceptions? We mapped out the sites to understand their configurations. The research considered on-site measurements of the environmental conditions and carried out modelling and simulations (ENVI-met V3.1) of the sites. Mathematical models (Wet-Bulb Globe Temperature (WBGT), Universal Thermal Climate Index (UTCI), and Standard Effective Temperature (SET)) were used to determine the thermal indices and the impact of the urban configurations on outdoor comfort. The thermal indices varied from 25.44 to 34.75 °C. In terms of the main contribution of this work, the results show that in hot and humid climate regions, urban configurations plus other design variables (e.g., orientation towards the Sun’s path) and environmental parameters influence occupants’ comfort and perceptions. Our findings show that high solar radiation and the need for a better thermal environment in hot and humid climates are the contributing factors for developing alternative urban configurations.
... RH variations are explained (R 2 = 0.701) by VSR, HDR, HFG, GnPR and OSRA [19]. Acero et al., (2021) [20] discussed the impact of urban design scenarios on OTC using the concept of Outdoor Thermal Comfort Autonomy (OTCA), conceived as per the research conducted by Nazarian et al., (2019) [55]. They reported that in E-W canyons, elevated levels of cloudiness decrease direct solar radiation, whereas higher solar exposure under clear skies exhibited uncomfortable OTC levels. ...
Modifying urban morphology, defined as mass, density, and orientation of building stock in cities, are well-known heat mitigation strategies addressing urban heat islands (UHI) at various scales and consequent thermal discomfort. However, varying morphological aspects may have divergent effects on Outdoor Thermal Comfort (OTC) in cities. Unlike UHI, which is derived from urban-rural temperature differences, OTC can be quantified by thermal comfort indices considering the objective assessment of microclimatic variables including air temperature (Ta), relative humidity (RH), mean radiant temperature (TMRT), and wind speed (Va), as well as a subjective assessment of individual perception. In Singapore and other tropical cities, thermally uncomfortable conditions prevail year-round due to higher Ta and RH coupled with high solar irradiance from its equatorial location. To better understand the relationship between density related morphological variables, microclimate conditions and OTC in Singapore, we first conduct a systematic literature review to identify existing research gaps and uncertainties. We subsequently analyse prominent building bylaws and urban planning codes of Singapore to understand the potential comfort implications of existing urban morphological norms. Finally, we propose a methodological framework on how to address the gaps and uncertainties in mainstream urban design and urban planning process keeping into consideration microclimatic, comfort and socio-economic variables.
... A second limitation planned to be addressed with further research is to ensure the method models a full set of representative days and weather types for a city. For this, weather clustering (Shobha and Asha, 2017;Acero et al., 2019;Nazarian et al., 2019) will be utilised to generate forcing data for the full range of weather condition types experienced in cities and allow the analysis of thermal comfort across the range of extreme heat days to warm down to extreme cold winter days. ...
Public health risks resulting from urban heat in cities are increasing due to rapid urbanisation and climate change, motivating closer attention to urban heat mitigation and adaptation strategies that enable climate-sensitive urban design and development. These strategies incorporate four key factors influencing heat stress in cities: the urban form (morphology of vegetated and built surfaces), urban fabric, urban function (including human activities), and background climate and regional geographic settings (e.g. topography and distance to water bodies). The first two factors can be modified and redesigned as urban heat mitigation strategies (e.g. changing the albedo of surfaces, replacing hard surfaces with pervious vegetated surfaces, or increasing canopy cover). Regional geographical settings of cities, on the other hand, cannot be modified and while human activities can be modified, it often requires holistic behavioural and policy modifications and the impacts of these can be difficult to quantify. When evaluating the effectiveness of urban heat mitigation strategies in observational or traditional modelling studies, it can be difficult to separate the impacts of modifications to the built and natural forms from the interactions of the geographic influences, limiting the universality of results To address this, we introduce a new methodology to determine the influence of urban form and fabric on thermal comfort, by utilising a comprehensive combination of possible urban forms, an urban morphology data source, and micro-climate modelling. We perform 9814 simulations covering a wide range of realistic built and natural forms (building, roads, grass, and tree densities as well as building and tree heights) to determine their importance and influence on thermal environments in urban canyons without geographical influences. We show that higher daytime air temperatures and thermal comfort indices are strongly driven by increased street fractions, with maximum air temperatures increases of up to 10 and 15 °C as street fractions increase from 10% (very narrow street canyons and/or extensive vegetation cover) to 80 and 90% (wide street canyons). Up to 5 °C reductions in daytime air temperatures are seen with increasing grass and tree fractions from zero (fully urban) to complete (fully natural) coverage. Similar patterns are seen with the Universal Thermal Climate Index (UTCI), with increasing street fractions of 80% and 90% driving increases of 6 and 12 °C, respectively. We then apply the results at a city-wide scale, generating heat maps of several Australian cities showing the impacts of present day urban form and fabric. The resulting method allows mitigation strategies to be tested on modifiable urban form factors isolated from geography, topography, and local weather conditions, factors that cannot easily be modified.
... It is more frequent that we find in the literature other terms associated with consciousness and even the use of climate consciousness, but without defining it directly. Thus, "climate-conscious growth," "climate-conscious design," "climate-conscious consumer," or "climate-conscious citizenship" are some of the concepts used to raise the consciousness of the human impact on the environment and our responsibility toward it (Erell, Portnov, and Etzion 2003;Gerlagh and Heijmans 2019;Nazarian, Acero, and Norford 2019;Andersen and Nielsen 2011). In 2016, Mary Robinson, the first female president of Ireland, who delivered a keynote address at the Summit of Conscience for the Climate, challenged the audience to be "climate-conscious" (Kerr and Parker 2019). ...
Individual responsibility and the development of “green virtues” are a rich field of exploration within the topic of climate change. However, despite the growing number of research dedicated to climate change, there is room for a better understanding of what climate change consciousness is. In this regard, the paper attempts to define climate change consciousness. There is a need to integrate climate change-related concerns into consciousness to understand this concept, which involves a radical transformation. For this, Romanian farmers’ level of climate change consciousness was assessed considering three layers: affective, cognitive, and conative. The “Introduction of new crops (not GMOs)” was the climate change adaptation measure adopted by most farmers. The variables that predicted the implementation of climate change adaptation measures were identified using regression analyses. The good prediction power of the moral values associated with different adaptation actions is an evidence of Romanian farmers’ climate change consciousness.
... To better utilize outdoor spaces, urban planning solutions (Section 5) could also be developed by incorporating adaptive behaviors in addition to environmental determinants (such as MRT and wind speed) responding to urban morphology and local climate (Nazarian, Acero, et al., 2019;Ng et al., 2011). Further examples of strategies that can promote climatically adaptive comfort behaviors at the individual scale include pedestrian routing recommendation engines to maximize exposure to shade resources (Deilami et al., 2020), development of cool street furniture (high thermal mass, low surface temperature, with vegetated awnings or shading), and active engagement in water-based recreation. ...
Urban overheating, driven by global climate change and urban development, is a major contemporary challenge that substantially impacts urban livability and sustainability. Overheating represents a multifaceted threat to the well‐being, performance, and health of individuals as well as the energy efficiency and economy of cities, and it is influenced by complex interactions between building, city, and global scale climates. In recent decades, extensive discipline‐specific research has characterized urban heat and assessed its implications on human life, including ongoing efforts to bridge neighboring disciplines. The research horizon now encompasses complex problems involving a wide range of disciplines, and therefore comprehensive and integrated assessments are needed that address such interdisciplinarity. Here, our objective is to go beyond a review of existing literature and instead provide a broad overview and integrated assessments of urban overheating, defining holistic pathways for addressing the impacts on human life. We (a) detail the characterization of heat hazards and exposure across different scales and in various disciplines, (b) identify individual sensitivities to urban overheating that increase vulnerability and cause adverse impacts in different populations, (c) elaborate on adaptive capacities that individuals and cities can adopt, (d) document the impacts of urban overheating on health and energy, and (e) discuss frontiers of theoretical and applied urban climatology, built environment design, and governance toward reduction of heat exposure and vulnerability at various scales. The most critical challenges in future research and application are identified, targeting both the gaps and the need for greater integration in overheating assessments.
... A second limitation planned to be addressed with further research is to ensure the method models a full set of representative days and weather types for a city. For this, weather clustering (Shobha and Asha, 2017;Acero et al., 2019;Nazarian et al., 2019) will be utilised to generate forcing data for the full range of weather condition types experienced in cities and allow the analysis of thermal comfort across the range of extreme heat days to warm down to extreme cold winter days. ...
Public health risks resulting from urban heat in cities are increasing due to rapid urbanisation and climate change, motivating closer attention to urban heat mitigation and adaptation strategies that enable climate-sensitive urban design and development. These strategies incorporate four key factors influencing heat stress in cities: the urban form (morphology of vegetated and built surfaces), urban fabric, urban function (including human activities), and background climate and regional geographic settings (e.g. topography and distance to water bodies). The first two factors can be modified and redesigned as urban heat mitigation strategies (e.g. changing the albedo of surfaces, replacing hard surfaces with pervious vegetated surfaces, or increasing canopy cover). Regional geographical settings of cities, on the other hand, cannot be modified and while human activities can be modified, it often requires holistic behavioural and policy modifications and the impacts of these can be difficult to quantify. When evaluating the effectiveness of urban heat mitigation strategies in observational or traditional modelling studies, it can be difficult to separate the impacts of modifications to the built and natural forms from the interactions of the geographic influences, limiting the universality of results. To address this, we introduce a new methodology to determine the influence of urban form and fabric on thermal comfort, by utilising a comprehensive combination of possible urban forms, an urban morphology data source, and micro-climate modelling. We perform 9814 simulations covering a wide range of realistic built and natural forms (building, roads, grass, and tree densities as well as building and tree heights) to determine their importance and influence on thermal environments in urban canyons without geographical influences. We show that higher daytime air temperatures and thermal comfort indices are strongly driven by increased street fractions, with maximum air temperatures increases of up to 10 and 15C as street fractions increase from 10% (very narrow street canyons and/or extensive vegetation cover) to 80 and 90% (wide street canyons). Up to 5C reductions in daytime air temperatures are seen with increasing grass and tree fractions from zero (fully urban) to complete (fully natural) coverage. Similar patterns are seen with the Universal Thermal Climate Index (UTCI), with increasing street fractions of 80% and 90% driving increases of 6 and 12C, respectively. We then apply the results at a city-wide scale, generating heat maps of several Australian cities showing the impacts of present day urban form and fabric. The resulting method allows mitigation strategies to be tested on modifiable urban form factors isolated from geography, topography, and local weather conditions, factors that cannot easily be modified.
... 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. ...
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.
... 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. ...
Cities are composed of a multitude of interconnected interactive layers and systems. The contemporary urban discourse has seen the utilization of Open data in decoding and understanding complex urban patterns that have eluded researchers for decades. Different layers of raw data from historical city cores up to the atmospheric climate have become more accessible, opening new horizons for multidisciplinary research. The rising complexity of cities calls for emerging approaches that can address the relationship between different layers of data—existing or emerging. In this regard, the current chapter is introducing and applying a methodology to use historical, spatial, and temporal datasets from Open Street Map (OSM) processed by Space Syntax superimposed on simulated urban microclimate dataset to find correlating patterns on how urban morphology has shaped the cities and the microenvironments over time. The outcomes for the case of Munich, illustrate the typologies that can be utilized in planning and developing design strategies to address micro-climate and accessibility in cities.KeywordsUrban morphologyUrban climateSpace syntaxMicroclimateGIS
... The envelopes should be integrated with the surrounding urban environment due to their shape and impact on this environment [23]. Shaping friendly and ecological buildings requires consideration of external comfort zones taking into account meteorological conditions, in which computer simulations are helpful [24][25]. Many modern complex materials allow building partitions throughout their area to function as such receivers [26][27]. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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. ...
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.
... To better utilize outdoor spaces, urban planning solutions (Section 5) could also be developed by incorporating adaptive behaviors in addition to environmental determinants (such as MRT and wind speed) responding to urban morphology and local climate (Nazarian, Acero, et al., 2019;Ng et al., 2011). Further examples of strategies that can promote climatically adaptive comfort behaviors at the individual scale include pedestrian routing recommendation engines to maximize exposure to shade resources (Deilami et al., 2020), development of cool street furniture (high thermal mass, low surface temperature, with vegetated awnings or shading), and active engagement in water-based recreation. ...
... To better utilize outdoor spaces, urban planning solutions (Section 5) could also be developed by incorporating adaptive behaviors in addition to environmental determinants (such as MRT and wind speed) responding to urban morphology and local climate (Nazarian, Acero, et al., 2019;Ng et al., 2011). Further examples of strategies that can promote climatically adaptive comfort behaviors at the individual scale include pedestrian routing recommendation engines to maximize exposure to shade resources (Deilami et al., 2020), development of cool street furniture (high thermal mass, low surface temperature, with vegetated awnings or shading), and active engagement in water-based recreation. ...
... 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). ...
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.
... 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]. ...
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
... 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). ...
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.
... 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 . ...
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.
... ) 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). ...
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. ...
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.
... 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. ...
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.
Improving people's thermal comfort in outdoor spaces is one of the most important goals of achieving the desirable design in these spaces. Today, the issue of thermal comfort in the " manufactured environment" is considered as a vital factor that affects health and the level of mental comfort of urban residents. Special attention to the issue of thermal comfort of people in outdoor spaces is of fundamental importance due to its direct impact on cognitive function and efficiency and as an important principle, it should be considered in the process of designing open urban spaces. Because comfortable outdoor spaces within urban fabrics can provide opportunities for people to participate and increase their social participation. Residential textures, as the core of urban areas, require high energy to meet the cooling and comfort needs of their residents. Also, this challenge stems from the undesirable design of these textures in modern times. It is essential to control "local micro- climate" in order to achieve the thermal comfort of the residents. The aim of this study was to investigate the micro-climate conditions
of old and middle textures of Shiraz city on a summer day with extreme heat stress, so that during the hottest hour of the day, the correlation between the geometry of old and middle textures with comfort index Thermal "PMV" was measured and the thermal comfort conditions in the old and middle textures were studied.
In order to conduct the present research, descriptive-analytical research method has been used in the context of library studies and quantitative measurement using two software ENVI-met 4 basic and SPSS. The most important advantage of this software is that it is one of the first models that seeks to produce the main processes in the atmosphere and calculates all the important meteorological factors. "Envi-met" software has been used in various studies, but in this study, the research method of those studies that have provided a basis for conducting our research has been studied. The aim of this research is to measure the thermal comfort on a hot summer day with the maximum air temperature in different climates, all studies have been done using " Envi-met " software and have been mainly based on "simulation". In this study, a simulation for the date of 21 July in the "thirty-year period" was performed. For this purpose, the weather data entered into the " Envi-met " software based on the 30-year weather data taken from the official sites of Shiraz city and using Autodesk Ecotect software for an average of 30 years, 21 July has been taken to simulate the hourly output that has been entered into the " Envimet " software for date of "21 July ". The "PMV" thermal comfort index for the selected areas located in the old and middle textures was extracted between 9 am and 16 pm and specifically at 15 pm with maximum temperature. Then, using "SPSS" statistical software to analyze the correlation between air temperature variables (° C), wind speed (m/s), relative humidity (%), Mean radiant temperature (° C) and urban geometry parameter "Sky view factor" with the "PMV" thermal comfort index at 15:00 pm in each of the "old and middle" textures. According to statistical analyzes and results obtained in both textures, it was found that in the middle texture, the correlation rate of "PMV" thermal comfort index with the variables of "Sky view factor" coefficient (0.885) and" Mean radiant temperature" (0.689) and in the old texture has a strong and positive correlation between "PMV" thermal comfort index and "wind speed" (0.935) and "Sky view factor" (0.762). It can be said that "Sky view factor" coefficient as one of
the components of urban texture geometry in both textures, has a very positive and direct correlation with "PMV" thermal comfort index. Also, according to the obtained outputs related to the thermal comfort index "PMV", in the old and middle texture and according to the 7- degree ASHRAE standard (ASHRAE Standard 55,2004: 2) related to the "PMV" index was determined. The old texture feels less heat stress than the middle texture between 9 a.m. and 16 p.m., and especially at 15 p.m. And it is in the range of more thermal comfort, which is due to the special geometric features of the old texture, such as the street orientation, aspect ratio and sky view factor compared to the middle texture. According to the results obtained related to the thermal comfort index "PMV", the selected points in both old and middle textures were determined that the old texture studied in time intervals and according to the Ashri standard, is in the range of low and medium heat stress and has more thermal comfort than the middle texture. Thus, the old and middle textures with their specific spatial layout, absorb different amounts of solar energy during the day and as a result, different levels of thermal comforts are created that organic urban layouts, such as old texture with higher levels of shading, are more efficient during the summer and provide more thermal comfort.
Climate change and rising temperatures are some of the biggest challenges tropical cities face. These cities need to be designed to accommodate high population growth while providing a comfortable thermal environment. In this context, we propose a framework for developing urban design guidelines with a focus on improving thermal comfort in outdoor environments, a concept known as Outdoor Thermal Comfort (OTC). The framework is based on computing climate variables such as temperature, wind speed, humidity, and others for several urban design strategies at the district scale. Furthermore, we use the spatial occupancy over the course of the day in the district to calculate an overall OTC performance score. Finally, the design strategies are ranked and represented in a three-dimensional space. The strategies are extracted from the body of knowledge of urban planning and design, and adjusted to local status and building codes. The climate variables are computed using numerical climate models, and the OTC performance score is calculated using a statistical risk management model. The guidelines discussed in this paper are limited to passive design strategies such as urban geometry, orientation and vegetation for tropical cities with high density. These guidelines can be used to support architects and urban planners in the early design stages of a new district.
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.
Attractive urban space is fundamental for creating safe and healthy cities. In the context of the climate crisis, microclimate becomes a determining factor for the use of public space in pursuing a just and equal society. Shifting to non-motorized modes of individual transport has manifold effects on the quality of urban environments in terms of safety, health, and spatial justice. Considering the need for quantifying microclimatic conditions in urban space, this chapter presents a methodology applied to a case study in the Boston Back Bay Area that develops a factor to indicate spatiotemporal outdoor comfort availability. The factor is based on a simulation workflow that generates datasets and maps, to be employed to quantify outdoor comfort availability at the pedestrian level with a high spatiotemporal resolution in adaptive spatial domains. The maps can be employed to compare different scenarios and neighbourhoods, and can serve as a base to put into evidence the influence of comfort and to formulate indications to increase outdoor thermal comfort in urban ecosystems. For promoting a tangible improvement of the city, pleasant environmental conditions are fundamental to accommodate pedestrian flows and to facilitate the implementation of social justice and public health.KeywordsUrban microclimateUrban morphologyUrban mobilityHuman health and well-beingBig data analytics
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.
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.
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.
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.
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.
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.
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.
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.
Outdoor thermal comfort is a major concern in urban areas throughout the world. Sophisticated modeling techniques have been developed to analyze the interaction of the urban areas with the regional climate. However, in most cases, the assessment of outdoor thermal comfort is not based on a long-term analysis and provides results only for specific meteorological conditions. In this study, we apply a clustering method to yearly weather files with the aim of obtaining representative boundary conditions for urban microclimatic models. The results describe typical-day weather situations commonly known as weather types. The study is carried out in the hot and humid tropical conditions of Singapore, where ten weather types are defined. The analysis of the clusters’ performance shows adequate results. ENVI-met (v.4.3) model is used to evaluate the impact of weather types on thermal comfort in a courtyard surrounded by high-rise buildings. Results not only show different levels of thermal comfort but also different spatial distribution and diurnal evolution inside the courtyard for each weather type. We conclude that it is relevant to analyze thermal comfort in all predominant weather conditions so as to have an accurate and complete assessment of the existing thermal situation. The approach presented in this study will provide better support to planners and decision makers in the development of urban spaces in regard to their expected use.
Urban green spaces offer vital ecosystem services such as regulating elevated temperatures in cities. Less information exists, however, on how urban green spaces influence outdoor thermal comfort (OTC), which is dependent on people’s perceptions of the complex interactions amongst ambient humidity, wind and both air and radiant temperatures. In this study, we analysed an existing OTC dataset compiled within a large Singapore urban park and calibrated OTC thresholds for physiological equivalent temperatures (PET) by analysing PET against thermal perception survey responses from the park visitors (n = 1508). We examined OTC according to (i) neutral, (ii) acceptable and (iii) preferred temperatures, where respondents felt ‘comfortable’ outdoors in the park. We estimated that neutral temperature, when all respondents experience neither heat nor cold stress, is 26.2 °C; acceptable temperatures, when only slight heat or cold stress is experienced, range between 21.6 and 31.6 °C; and preferred (‘ideal’) temperature for all respondents is 24.2 °C. Respondents residing for more than 6 months in Singapore achieved thermal neutrality, suggesting that a greater degree of thermal adaptation likely developed during acclimatisation to local climate through a combination of physiological, behavioural and psychological circumstances. Comparisons with other OTC studies showed differences in synoptic climates are linked to variations in the magnitude and ranges of perceived PET. Lastly, respondents in this study perceived lower neutral and preferred temperatures compared to respondents surveyed over a variety of urban land use categories in another local study. The differences in neutral and preferred temperatures between studies suggest that lower park temperatures and different environmental attitudes influence perceived OTC.
Urban morphology and inter-building shadowing result in a non-uniform distribution of surface heating in urban areas, which can significantly modify the urban flow and thermal field. In Part I, we found that in an idealized three-dimensional urban array, the spatial distribution of the thermal field is correlated with the orientation of surface heating with respect to the wind direction (i.e. leeward or windward heating), while the dispersion field changes more strongly with the vertical temperature gradient in the street canyon. Here, we evaluate these results more closely and translate them into metrics of “city breathability,” with large-eddy simulations coupled with an urban energy-balance model employed for this purpose. First, we quantify breathability by, (i) calculating the pollutant concentration at the pedestrian level (horizontal plane at z≈1.5–2 m) and averaged over the canopy, and (ii) examining the air exchange rate at the horizontal and vertical ventilating faces of the canyon, such that the in-canopy pollutant advection is distinguished from the vertical removal of pollution. Next, we quantify the change in breathability metrics as a function of previously defined buoyancy parameters, horizontal and vertical Richardson numbers (Rih and Riv, respectively), which characterize realistic surface heating. We find that, unlike the analysis of airflow and thermal fields, consideration of the realistic heating distribution is not crucial in the analysis of city breathability, as the pollutant concentration is mainly correlated with the vertical temperature gradient (Riv) as opposed to the horizontal (Rih) or bulk (Rib) thermal forcing. Additionally, we observe that, due to the formation of the primary vortex, the air exchange rate at the roof level (the horizontal ventilating faces of the building canyon) is dominated by the mean flow. Lastly, since Rih and Riv depend on the meteorological factors (ambient air temperature, wind speed, and wind direction) as well as urban design parameters (such as surface albedo), we propose a methodology for mapping overall outdoor ventilation and city breathability using this characterization method. This methodology helps identify the effects of design on urban microclimate, and ultimately informs urban designers and architects of the impact of their design on air quality, human health, and comfort.
As urbanization progresses, more realistic methods are required to analyze the urban microclimate. However, given the complexity and computational cost of numerical models, the effects of realistic representations should be evaluated to identify the level of detail required for an accurate analysis. We consider the realistic representation of surface heating in an idealized three-dimensional urban configuration, and evaluate the spatial variability of flow statistics (mean flow and turbulent fluxes) in urban streets. Large-eddy simulations coupled with an urban energy balance model are employed, and the heating distribution of urban surfaces is parametrized using sets of horizontal and vertical Richardson numbers, characterizing thermal stratification and heating orientation with respect to the wind direction. For all studied conditions, the thermal field is strongly affected by the orientation of heating with respect to the airflow. The modification of airflow by the horizontal heating is also pronounced for strongly unstable conditions. The formation of the canyon vortices is affected by the three-dimensional heating distribution in both spanwise and streamwise street canyons, such that the secondary vortex is seen adjacent to the windward wall. For the dispersion field, however, the overall heating of urban surfaces, and more importantly, the vertical temperature gradient, dominate the distribution of concentration and the removal of pollutants from the building canyon. Accordingly, the spatial variability of concentration is not significantly affected by the detailed heating distribution. The analysis is extended to assess the effects of three-dimensional surface heating on turbulent transfer. Quadrant analysis reveals that the differential heating also affects the dominance of ejection and sweep events and the efficiency of turbulent transfer (exuberance) within the street canyon and at the roof level, while the vertical variation of these parameters is less dependent on the detailed heating of urban facets.
Urban greenery is a favoured approach applied towards reducing urban warmth and climate discomfort, but ascertaining its measured and perceived effectiveness in tropical climates is relatively understudied. To this end, we investigated microclimate differences within an urban park (the Singapore Botanic Gardens) to assess if variations in plot-scale land cover affect both objective (measured) and subjective (surveyed) microclimate data. Over two monsoonal seasons, we obtained data from four distinct sites–a tropical rainforest stand, a palm tree valley, a water-body feature, and the park visitors’ centre. Measured climate data (e.g. air temperature, vapour pressure, wind velocity and globe temperatures) were used to derive mean radiant temperature Tmrt and three thermal comfort indices (e.g. temperature-humidity index THI, physiological equivalent temperature PET, and wet-bulb globe temperature WBGT). Concurrent to these measurements, we also surveyed park users (n = 1573) for perceived microclimate sensations and preferences in thermal, humidity, wind and sun exposure, as well as their overall assessment of climate comfort/discomfort. The results indicate significant differences in both measured and perceived microclimates over different sites and seasons, with (i.) selected heat stress thresholds based on thermal comfort indices exceeded at several sites, and (ii.) visitors perceived generally hot, humid and low-wind conditions throughout. Variations in respondent acclimatisation to tropical climates are observed between correlations of WBGT and some sensation votes, with apparently stronger correlations with more acclimated respondents. While humidity was voted as the most uncomfortable climate variable across all sites, a large majority of respondents felt comfortable climate conditions throughout. Present results confirm that vegetation canopy characteristics affecting wind and sun exposure appear to be important factors in outdoor thermal comfort. Lastly, we suggest that future tropical outdoor thermal comfort studies consider the critical aspects of site humidity and wind to discern comfort/discomfort levels.
Optimal positioning of workstations in perimeter offices is a key factor affecting visual comfort and satisfaction, depending on façade design and control. Visual comfort is related to different factors, such as daylight glare and light adequacy. In addition, connection to the outdoors, delivered through window views, is related to the amount of view as well as view clarity. This study presents a new approach to evaluate office workplaces in terms of overall visual environment. Visual comfort, daylight provision and outside view are used as the three basic criteria. A new index, the Effective Outside View (EOV), is introduced to characterize the connection to the outdoors considering the amount and clarity of outside view. In addition, the Visual Comfort Autonomy (VCA) is defined as the portion of time when visual comfort criteria, based on vertical illuminance on the eye, are satisfied. The spatial variation of these indices and continuous daylight autonomy are used to evaluate perimeter offices with glass facades and window shades. Detailed simulations, based on a validated daylighting-glare model, are used to evaluate visual conditions for different occupant positions and main view directions. A case study is presented for an open plan office with different façade orientations. Selected glazing and shading properties are used as an example to present results on appropriate seating configurations in order to reduce the risk of glare and maximize daylight use, while maintaining effective outside view. This study, along with future occupant surveys, will help define clear regulations and guidelines for comfortable daylit indoor environments.
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.
This paper presents a method to produce long term climatic forcing fields to force SVAT models in off-line mode. The objective is to increase the temporal frequency of existent climate projections databases from daily frequency to hourly time step to be used in impact climate studies. A statistical clustering k-means method is used. A tens of clusters seems to be enough to describe the climate variability in term of wind regimes, precipitation and thermal and humidity amplitude. These clusters are identified in the future projections of climate and reconstructed sequences at hourly frequency are obtained for all the forcing variables needed by a SVAT model, typically: air temperature, specific humidity, wind force and direction, precipitation, direct short-wave radiation, downward long-wave radiation and scattered short-wave radiation. Ten years of observations from two sites in France are used to illustrate the method: the Chartres station (Paris) and Blagnac station (Toulouse). The reconstruction algorithm is able to produce diurnal cycles that fits well with hourly series from observations (1998-2008; 1961-1990) and from climatic scenarios (1961-2100). The diurnal amplitude and mean value is well represented for variables with marked daily cycle as temperature or humidity. Changes in the mean wind direction are represented and, to a certain extent, changes in wind intensity are also retained. The mean precipitation is conserved during the day even if the method is not able to reproduce the short rain picks variability. Precipitation is used as input in the clusterization process so in clusters representative of rainy days some diurnal variability is nevertheless retained.
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.
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.
The effect of urban development on local thermal climate is widely documented in scientific literature. Observations of urban–rural air temperature differences—or urban heat islands (UHIs)—have been reported for cities and regions worldwide, often with local field sites that are extremely diverse in their physical and climatological characteristics. These sites are usually described only as “urban” or “rural,” leaving much uncertainty about the actual exposure and land cover of the sites. To address the inadequacies of urban–rural description, the “local climate zone” (LCZ) classification system has been developed. The LCZ system comprises 17 zone types at the local scale (102 to 104 m). Each type is unique in its combination of surface structure, cover, and human activity. Classification of sites into appropriate LCZs requires basic metadata and surface characterization. The zone definitions provide a standard framework for reporting and comparing field sites and their temperature observations. The LCZ system is designed primarily for urban heat island researchers, but it has derivative uses for city planners, landscape ecologists, and global climate change investigators.
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.
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.
A classification of weather patterns (WP) is derived that is tailored to best represent situations relevant for the urban heat island (UHI). Three different types of k-means-based cluster methods are conducted. The explained cluster variance is used as a measure for the quality. Several variables of the 700-hPa fields from the 40-yr ECMWF Re-Analysis (ERA-40) were tested for the classification. The variables as well as the domain for the clustering are chosen in a way to explain the variability of the UHI as best as possible. It turned out that the combination of geopotential height, relative humidity, vorticity, and the 1000-700-hPa thickness is best suited. To determine the optimal cluster number k several statistical measures are applied. Except for autumn (k = 12) an optimal cluster number of k = 7 is found. The WP frequency changes are analyzed using climate projections of two regional climate models (RCM). Both RCMs, the Regional Model (REMO) and Climate Limited-Area Model (CLM), are driven with the A1B simulations from the global climate model ECHAM5. Focusing on the periods 2036-65 and 2071-2100, no change can be found of the frequency for the anticyclonic WP when compared with 1971-2000. Since these WPs are favorable for the development of a strong UHI, the frequency of strong UHI days stays the same for the city of Hamburg,Germany. For other WPs changes can be found for both future periods. At the end of the century, a large increase (17%-40%) in the frequency of the zonal WP and a large decrease (20%-26%) in the southwesterly WP are projected.
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.
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.
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.
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
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.
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.
Over the past century, many research studies have been conducted in an attempt to define thermal conditions for humans in the outdoor environment and to grade thermal sensation. Consequently, a large number of indices have been proposed. The examination of human thermal indices by thermal subjective perception has become recently a methodical issue to confirm the accuracy, applicability and validation of human thermal indices. The aims of this study are: (a) to review studies containing both calculated human thermal conditions and subjective thermal perception in the outdoor environment (b) to identify the most used human thermal indices for evaluating human thermal perception (c) to examine the relation between human thermal comfort range and outdoor thermal environment conditions and (d) to compare between categories of thermal sensation in different climatic zones based on subjective perception and levels of thermal strain. A comprehensive literature review identified 110 peer-reviewed articles which investigated in-situ thermal conditions versus subjective thermal perception during 2001-2017. It seems that out of 165 human thermal indices that have been developed, only 4 (PET, PMV, UTCI, SET*) are widely in use for outdoor thermal perception studies. Examination of the relation between human thermal comfort range and outdoor thermal environment conditions for selective indices in different climatic zones shows that the range of the thermal comfort or dis-comfort is affected by the outdoor thermal environment. For the PET index, the "neutral" range for hot climates of 24-26°C is agreed by 95% of the studies where for cold climate, the "neutral" range of 15-20°C is agreed by 89% of the studies. For the UTCI, the "no thermal stress" category is common to all climates. The "no stress category" of 16-23°C is agreed by 80% of the case studies, while 100% of the case studies agreed that the range is between 18 and 23°C.
With the rapid rate of urbanization, outdoor thermal comfort is a growing health concern in densely-built areas. Accordingly, in order to achieve a comprehensive solution to urban environmental problems, more detailed and accurate prediction of outdoor thermal comfort is needed alongside building energy and urban wind flow analyses. To address this need, this study introduces an improved methodology of predicting outdoor thermal comfort and its spatial variability in urban streets using the comprehensive index standard effective temperature (SET). The improvement of the thermal comfort calculation is twofold. First, CFD simulations of the flow field dynamically coupled with the realistic urban surface heating are used to provide the input variables for the SET calculation. The CFD results provide detailed information on the heterogeneous urban flow field as a critical determinant of human comfort. Second, the SET calculations are improved by introducing a detailed model of mean radiant temperature that incorporates a) the visibility of urban surfaces to the pedestrians at any point, b) the spatial distribution of sky view factor, and c) inter-building shadowing and shortwave radiation effects on thermal comfort. These improvements allow for evaluating the spatial distribution of SET. Additionally, several sensitivity studies are carried out for an idealized configuration representing a compact low rise urban zone. The SET evaluated at the pedestrian level shows that urban density, wind patterns, and solar position concurrently influence thermal comfort. A sensitivity study on the effect of urban density reveals that higher urban concentration can favourably impact thermal comfort in warm climates due to the increased shading, despite the associated increase in air temperature and building energy consumption. The current study also demonstrates the critical importance of a comprehensive thermal comfort model that considers the flow field patterns as well as the realistic heating distribution of urban surfaces. We find that even in the shaded areas in the street canyon, SET changes up to 10 °C due to the wind sheltering in the urban roughness. Following this methodology, more complex scenarios can be evaluated in order to evaluate the effect of urban design on thermal comfort, and ultimately achieve a climate-conscious design.
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.
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.