Outdoor Human Thermal Comfort Research Articles

High-resolution multi-scaling of outdoor human thermal comfort and its intra-urban variability based on machine learning

Abstract. As the frequency and intensity of heatwaves will continue to increase in the future, accurate and high-resolution mapping and forecasting of human outdoor thermal comfort in urban environments are of great importance. This study presents a machine-learning-based outdoor thermal comfort model with a good trade-off between computational cost, complexity, and accuracy compared to common numerical urban climate models. The machine learning approach is basically an emulation of different numerical urban climate models. The final model consists of four submodels that predict air temperature, relative humidity, wind speed, and mean radiant temperature based on meteorological forcing and geospatial data on building forms, land cover, and vegetation. These variables are then combined into a thermal index (universal thermal climate index – UTCI). All four submodel predictions and the final model output are evaluated using street-level measurements from a dense urban sensor network in Freiburg, Germany. The final model has a mean absolute error of 2.3 K. Based on a city-wide simulation for Freiburg, we demonstrate that the model is fast and versatile enough to simulate multiple years at hourly time steps to predict street-level UTCI at 1 m spatial resolution for an entire city. Simulations indicate that neighbourhood-averaged thermal comfort conditions vary widely between neighbourhoods, even if they are attributed to the same local climate zones, for example, due to differences in age and degree of urban vegetation. Simulations also show contrasting differences in the location of hotspots during the day and at night.

Analysis of thermal discomfort associated with synoptic conditions in the city of Pelotas, southernmost region of Brazil.

Here, we evaluated the influence of outdoor environmental conditions (synoptic weather conditions) on human thermal discomfort in the five macro-regions of Pelotas city, located in the southernmost region of Brazil. To do this, meteorological sensors (HOBO MX2301A) were installed outside the residences to measure the air temperature, dew point temperature, and relative humidity between 18 January and 20 August 2019. Two well-established simplified biometeorological indices were examined seasonally: (i) humidex for the summer months and (ii) effective temperature as a function of wind for the autumn and winter months. Our findings showed seasonal differences related to human thermal discomfort and outdoor environmental conditions. The thermal discomfort was highest in the afternoons during the summer months and at night during the winter months. The seasonal variation in human thermal discomfort was highly associated with the meteorological conditions. In summer, the presence of the South Atlantic Subtropical Anticyclone (SASA) contributed to heat stress. The SASA combined with the continent's low humidity contributed to the perceived sensation of thermal discomfort. In the winter, thermal discomfort was associated with the decrease in air humidity caused by high atmospheric pressure systems, which led to a decrease in both air temperature and air moisture content. Our findings suggest that a better understanding of the complex interplay between outdoor environmental factors and human thermal comfort is needed in order to mitigate the negative effects of thermal discomfort.

Improving Pedestrian Thermal Comfort Using Optimized Urban Trees Pattern in Aswan City

For long periods last years, the majority of cities suffer from exceptionally hot- dry climate. However, the most urban patterns within these cities are unsuitable for these severe occurrences and raise the value of the Urban Heat Island (UHI). The goal of this study is to see how UHI mitigation options affect outdoor human thermal comfort in three different forms of frequent urban trees patterns in the world’s most populous city in Egypt, Aswan. The ENVI-met model was utilised to assess meteorological using simulation climate program (Ecotect Analysis), buildings and vegetation distribution, using Pupulus Alba. All measurements were taken in a pedestrian walkway at the microclimate case study (case 1. without trees, case 2. distribution trees each 8m total coverage 50%, case 3. distribution trees each 12m total coverage 21.5% were conducted to measure, relative humidity, mean radiant temperature, wind speed, air temperature and prediction mean vote as a key indicator for human thermal comfort. This study provided a better understanding of the role of Urban Heat Island UHI mitigation strategies on human thermal comfort in the outdoor spaces of Aswan’s residential neighborhoods. The simulation results revealed high thermal comfort and discomfort after setting 3 cases for trees pattern for the climate and the possible vegetation (trees patterns). This result indicate that an optimized percentage of urban trees pattern can mitigate (UHI) effect and clear the role that urban trees serve in modifying microclimates.

Simulating the effect of urban sprawl on air quality and outdoor human thermal comfort in a cold city, Erzurum, Turkey.

Research on climate-sensitive urban planning is important to improve the quality of city life. Cold climate cities should respect climatic characteristics to diversify outdoor uses and increase air quality to maximize the benefits of winter. This study is aimed to explore the impact of changing urban pattern on air pollution and outdoor human thermal comfort conditions (HTCCs) in a newly developed urban area in Şükrüpaşa neighbourhood, Erzurum, among the coldest cities in Turkey, with high PM10 and low HTCCs levels. Sensitivity of urban development pattern to climate conditions and its suitability to eliminate the winter disturbances caused by HTCCs and air pollution were investigated by producing maps for HTCCs and air pollution using morphological, meteorological and spatial data and ENVI-met model in winter period of 2017 and 2022. It was found that newly developed areas increase the unfavourable conditions in terms of air quality, temperature and HTCCs due to the reasons like improper land uses, urban sprawl, high urban density and ventilation problems. In high-elevated cold cities, spatial planning and design principles should strictly be followed by incorporating climate knowledge and without revising the spatial decisions.

Scalable nanofibrous silk fibroin textile with excellent Mie scattering and high sweat evaporation ability for highly efficient passive personal thermal management

Passive personal thermal management based on radiative cooling textiles is emerging as a facile, cost-effective, and energy-efficient way for outdoor human body thermal comfort. Existing passive radiative cooling textiles are mainly built from synthetic polymers that are usually nonrenewable and non-degradable, and lack sweat management function. Herein, we report the fabrication of a biopolymer-based, nanofibrous textile that integrates passive radiative cooling and sweat transportation functions via a scalable electrospinning technique. The optimized control over the nanofibers’ diameter enables the 200 µm thick film with high reflectance in both the ultraviolet (UV) range (92%) and the entire solar spectrum (95%), and the abundant chemical bonds of silk fibroin allow a high emissivity of 95% in the atmospheric window. Consequently, the nanostructured textile can achieve a temperature of ∼3.8 °C below the ambient temperature during the daytime and ∼6.4 °C at night. More importantly, the use of hygroscopic silk fibroin offers additional functions of sweat absorption and evaporation. Outdoor sweat evaporation experiment demonstrates a temperature reduction of ∼5.5 °C for nanofibrous silk fibroin textile, compared with the traditional nonhygroscopic textile. Owing to its excellent combination of biodegradability, superior cooling ability, and high sweat transportation capacity, the scalable silk nanofabric would be an effective textile for passive personal thermal management.

Outdoor Human Thermal Comfort along Bike Paths in Balneário Camboriú/SC, Brazil

This research is concerned with understanding the degree of human thermal (dis)comfort in connection with the various microclimates present in the vicinity of bike trails in Balneário Camboriú/SC, Brazil, throughout the summer. Local Climate Zones were determined using the Sky View Factor and were identified along research routes and schedules at 9:00 a.m. and 4:00 p.m. on a subtropical summer day (14 January 2022). Data were collected with weather devices attached to the bicycle, measuring air temperature, relative humidity, and globe temperature, from which the mean radiant temperature was calculated. The PET and UTCI indices were used to assess outdoor thermal comfort in the summer. The findings revealed that at 9:00 a.m., the eastern half of the city had a higher tendency for thermal discomfort; however, at 4:00 p.m., this same location had thermal comfort for users along bike routes. At 4:00 p.m., the PET index indicated that 24% of the bike paths were pleasant, and the UTCI index indicated that 100% of them were in thermal comfort. At 9:00 a.m., the majority of the city was under discomfort conditions. The index values reflect the morning time, and the study shows that there is now a negative correlation between the SVF and the indexes, which means that the greater the SVF computations, the lower the values are. The PET and UTCI indices revealed a positive association in the afternoon period: The greater the SVF values, the higher the PET and UTCI indices. Further research should be conducted in the future because many parameters, such as construction, position, and urban (im)permeability, as well as sea breeze and solar radiation, can have a significant impact on outdoor human thermal comfort in Balneário Camboriú, and when combined with the type of LCZ and the SVF, it is possible to understand how all of these active systems interact and form microclimates that are beneficial to bike path users.

Linking landscape spatial heterogeneity to urban heat island and outdoor human thermal comfort in Tokyo: Application of the outdoor thermal comfort index

Rapid urbanization and high-density development are major drivers of global warming. The associations of spatial landscape patterns with urban thermal environments have been extensively investigated. Meanwhile, quantifying the cooling effects of landscape patterns on street-level outdoor thermal comfort has been less attempted. This study examined the relationship between the spatial heterogeneity of landscape patterns and urban residents’ outdoor thermal comfort in Tokyo, Japan. The cooling effects of the greenery pattern – configurations and compositions – on thermal comfort were explored while considering the interaction effects of greenery patterns with water bodies and urban densities. Our study findings indicated that spatial landscape patterns have a statistically significant impact on outdoor thermal comfort, showing 69% of explanatory power (Adj-r2) in the spatial error model. The cooling effects of greenery were improved when their spatial patterns were in a more aggregated, less fragmented, and less complex shape. Furthermore, outdoor thermal stress was relatively lower when there was simple shape greenery in low-density areas or complex shapes but in high-density areas while indicating synergies between them. Our findings would provide microclimatic urban planning and design implications of how to spatially configure urban greenery to improve outdoor thermal comfort.

Model of Spectral and Directional Radiative Transfer in Complex Urban Canopies with Participating Atmospheres

Thermal heat transfers, including solar and infrared radiation in cities, are key processes for studying urban heat islands, outdoor human thermal comfort, energy consumption, and production. Thus, accurate radiative transfer models are required to compute the solar and infrared fluxes in complex urban geometry accounting for the spectral and directional properties of the atmosphere and city fabric materials. In addition, these reference models may be used to evaluate existing parametrization models of radiative heat transfer and to develop new ones. The present article introduces a new reference model for outdoor radiative exchange based on the backward Monte Carlo method. The integral formulations of the direct and scattered solar, and the terrestrial infrared radiative flux densities are presented. This model can take into account the ground (e.g., roads, grass), different types of buildings and vegetation (e.g., trees consisting of opaque leaves and trunks) with their spectral and directional (Lambertian and specular) reflectivity of materials. Numerical validations of the algorithm are presented against the results of a state-of-the-art model based on the radiosity method for the particular case of an infinitely long street canyon. In addition, the convergence of urban solar radiation budgets is studied for a selection of urban complex geometries including or not the window glazing. Good convergence is found for all geometries, even in the presence of rare events due to specular reflections.

Improvements, extensions, and validation of the Urban Weather Generator (UWG) for performance-oriented neighborhood planning

Policymakers have to assess and optimize neighborhood-scale planning aspects to profit from climate mitigation and adaptation measures due to various thermal environmental concerns. There are many models to evaluate the local thermal environment, but their outputs or complexity limit their application in performance-oriented neighborhood planning. In this study, the Urban Weather Generator (UWG) was updated to meet the needs of neighborhood planners. The model improves the radiation, vegetation, and convective heat transfer calculation processes to better match the actual physical representation of the neighborhood. Besides, the functions of the model are extended to calculate the mean radiant temperature (MRT) and water temperature for the evaluation of outdoor human thermal comfort and blue infrastructure effects. A new graphical interface also makes it easier for planning decision-makers to start quickly. Then, the prediction results of the updated model are evaluated with the neighborhood observations of the hot and humid regions of Guangzhou and Nanning. The air temperature, relative humidity (RH), and MRT results revealed that this novel model performs quite consistently and demonstrated the reliability and computational efficiency of the UWG model. In the early stages of thermal environment evaluation, the UWG model can be used for performance-oriented neighborhood planning.

A Comparative Study of Cooling Performance and Thermal Comfort under Street Market Shades and Tree Canopies in Tropical Savanna Climate

Walking through street markets is the most popular outdoor activity in Thailand, promoting local economies and tourism. In the year-round hot and humid conditions, living outdoors with long heat exposure throughout the midday can result in heat-related illness. Artificial shade structures and tree shade canopies are typical cooling strategies to protect market sellers and pedestrians from direct sun exposure and improve outdoor human thermal comfort in the street market. This study investigates microclimate conditions and cooling benefits of typical street market shade structures with different settings—three roofing materials, two roof shapes, and surrounding trees with dense and sparse canopies. The dimension of the single artificial shade was 2 m × 2 m with heights varying 2–2.5 m. The vertical air temperature and sky view factor profiles were measured on winter and summer days. The calculated physiological equivalent temperatures (PET) and thermal comfortable hours beneath different shade structures were assessed using RayMan 1.2 software. A cluster of trees with a dense canopy provided more effective cooling (with a satisfied thermal condition of 9 h) than artificial shade structures. Thermal conditions under the galvanized steel roofing and HDPE tarpaulin plastic roofing shades were cooler than those of polycarbonate roofing shade. Meanwhile, the space beneath the sparse tree canopy had the warmest condition. The temperature reductions beneath the artificial shade structure varied throughout the day, with the maximum reduction occurring during midday and the lowest reduction found in the late morning and late afternoon. Our study demonstrates that the tree canopies and artificial shade structures had limited application for providing comfortable conditions throughout midday. To reduce such extreme heat, a combination of shade structures with other cooling techniques is suggested, which should be the focus for further studies.

Linking Landscape Spatial Heterogeneity to Urban Heart Island and Outdoor Human Thermal Comfort in Tokyo: Application of the Outdoor Thermal Comfort Index

Linking Landscape Spatial Heterogeneity to Urban Heart Island and Outdoor Human Thermal Comfort in Tokyo: Application of the Outdoor Thermal Comfort Index

The influence of perceived environmental quality on thermal comfort in an outdoor urban environment during hot summer

Thermal comfort in outdoor spaces is essential for human health and human wellbeing. A comfortable outdoor space enhances urban livability and sustainability. Previous studies on outdoor human thermal comfort highlighted that apart from the microclimate conditions, the psychological and physiological factors play an important role in human thermal comfort. The influence of environmental quality on human thermal comfort is being examined in this paper. A survey with a total of 1842 thermal comfort responses was conducted during a hot summer in Hong Kong. Perceived aesthetic and acoustic quality votes are strongly associated with Thermal Sensation Votes (TSV). Thermal Comfort Votes (TCV) in the satisfied aesthetic group and the satisfied acoustic group are significantly higher than that in the not satisfied group. A sensation of comfort was confirmed by 39.8% and 38.4% of participants in the satisfied aesthetic group and the satisfied acoustic group, while only 22.2% and 23.9% of the members of the not satisfied group felt comfortable. The study suggested that the perceived environmental qualities are highly associated with thermal sensation and thermal comfort, and a beautiful and quiet environment can improve the thermal comfort and thermal tolerance.

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

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

The Use of Cool Pavements for the Regeneration of Industrial Districts

Industrial districts are characterized by the presence of low and extensive building volumes and by predominantly sealed, impermeable surfaces, which contribute to several environmental problems and to the deterioration of outdoor human thermal comfort conditions, especially during summer hot days. To tackle these issues, this study proposes an approach for the regeneration of industrial districts based on the application of cool materials. Reflective and evaporative pavements were selected as suitable solutions to reduce summer overheating, while ensuring the functionality required by the industrial production, and contributing to stormwater management. The effectiveness of the approach was tested in a portion of the industrial district of Padua (Italy). In summer conditions, the replacement of conventional pavements with cool materials results in a reduction of the ground surface temperatures up to 14.0 °C and a consequent decrease of the air temperature at pedestrian level between 0.6 and 1.2 °C. The effects of human thermal comfort conditions highly depend on the selected cool material and on the morphology of the urban canyon. Finally, the reduction of external surface and air temperatures also contributes in cooling indoor spaces (average decrease from 1.0 to 2.5 °C), with impacts on the energy efficiency of the industrial buildings.

Trade-Offs between Urban Green Space and Densification: Balancing Outdoor Thermal Comfort, Mobility, and Housing Demand

Urban green spaces reduce elevated urban temperature through evaporative cooling and shading and are thus promoted as nature-based solutions to enhance urban climates. However, in growing cities, the supply of urban green space often conflicts with increasing housing demand. This study investigates the interplay of densification and the availability of green space and its impact on human heat stress in summer. For the case of an open-midrise (local climate zone 5) urban redevelopment site in Munich, eight densification scenarios were elaborated with city planners and evaluated by microscale simulations in ENVI-met. The chosen scenarios consider varying building heights, different types of densification, amount of vegetation and parking space regulations. The preservation of existing trees has the greatest impact on the physical equivalent temperature (PET). Construction of underground car parking results in the removal of the tree population. Loss of all the existing trees due to parking space consumption leads to an average daytime PET increase of 5°C compared to the current situation. If the parking space requirement is halved, the increase in PET can be reduced to 1.3°C–1.7°C in all scenarios. The addition of buildings leads to a higher gain in living space than the addition of floors, but night-time thermal comfort is affected by poor ventilation if fresh air circulation is blocked. The protection of mature trees in urban redevelopment strategies will become more relevant in the changing climate. Alternative mobility strategies could help to reduce trade-offs between densification and urban greening.<p>Urban green spaces reduce outdoor temperatures through evaporative cooling and shading and are thus promoted as nature based solutions to enhance urban climates. However, in growing cities, supply of urban green space often conflicts with increasing housing demand. This study investigates the interplay of densification and availability of green and its impact on outdoor human thermal comfort. For the case of an open-midrise (LCZ 5) urban redevelopment site in Munich, eight densification scenarios were elaborated with city planners and evaluated by microclimate modelling in ENVI-met. The chosen scenarios consider varying building heights, different types of densification, vegetation amount and parking space regulations. The greatest impact on physical equivalent temperature (PET) has the preservation of existing trees. Construction of underground car parking results in the removal of the tree population. Loss of all existing trees due to parking space consumption leads to an average daytime increase of 5 °C PET compared to the current situation. If the parking space requirement is halved, the increase in PET can be reduced to 1.3 to 1.7 °C in all scenarios. Adding buildings leads to a higher gain in living space than adding floors, yet night time thermal comfort is affected by poor ventilation if fresh air circulation is blocked. Protecting mature trees in urban redevelopment strategies will gain more relevance in changing climate. Alternative mobility strategies can help to reduce trade-offs between mobility, densification and microclimate.</p>

Urban Thermal Comfort: Analyzing the Impact of 'Reviva Centro' Revitalization on Campo Grande's Urban Microclimate

This study evaluates the impact of green infrastructure as a strategy for mitigating the adverse effects of urbanization and enhancing outdoor thermal comfort. Focusing on the 'Reviva Centro' urban revitalization project in downtown Campo Grande, Mato Grosso do Sul, Brazil, the research compares two scenarios along '14 de Julho' street: the pre-revitalization state and the post-implementation condition. Utilizing the Envi-met program for 3D modeling and microclimatic simulation, this study examines the interplay between urban surfaces, vegetation, and atmospheric conditions, analyzing four key variables: temperature, relative humidity, wind speed, and direction. The assessment of outdoor human thermal comfort is based on the equivalent physiological temperature (PET).
 The simulation results indicate a significant improvement in thermal comfort both during cold and hot times of the day. At 8 am, an increase in air temperature by 6°C was observed, reducing discomfort from cold. Conversely, at 4 pm, a decrease in air temperature by 4.98°C was noted, enhancing comfort in the post-revitalization scenario. These findings underscore the effectiveness of urban vegetation in regulating the urban microclimate and improving pedestrian comfort, demonstrating its critical role in urban environmental strategies."

Interrelationships between Land Use Land Cover (LULC) and Human Thermal Comfort (HTC): A Comparative Analysis of Different Spatial Settings

A few studies on outdoor human thermal comfort (HTC) have been conducted in the tropical region in a hot and humid climate; however, there is a paucity of discussions on how exactly different spatial settings influence HTC. Thus, this paper aims to examine how land use land cover (LULC) affects HTC on the basis of the simulation of Predicted Mean Vote (PMV) and Physiologically Equivalent Temperature (PET) indices via ENVI-met and Rayman. The results reveal that people living in the urban area have a higher tendency to experience strong heat stress (25% of the areas with PMV ranging from 3.4 to 3.9 and 2% of the areas, where PMV reached 4.1), followed by the rural area (43% of the areas with PMV ranging from 2.1 to 2.4), and the suburban area (more than 50% of the areas with PMV values less than 2.4). Surprisingly, a concrete LULC in the suburb area exhibits a higher air temperature than an asphalt surface at 4 p.m., due to the large area of high albedo that increases the reflection of solar radiation, subsequently contributing to warming up the airmass. Similarly, sandy, and loamy LULC tend to emit more heat during nighttime, while the heat is absorbed slowly during daytime, and it is then slowly released during nighttime after 6 p.m. Spatial settings that promote heat stress in the urban area are mainly contributed by an LULC of asphalt, concrete, sandy, and loamy areas. Meanwhile, people in the suburban and rural areas are less likely to experience heat stress, due to agricultural plantations and lowland forest that provide shade, except for the barren lands-loamy areas. The result also indicates that tree-covered areas near the river in the suburban area afforded the best thermal experience with PMV of 2.1 and PET of 30.7. From the LULC comparison, it is pivotal to consider tree species (canopy density), surface material (albedo), sky-view factor, wind direction, and speed toward designing a more comfortable and sustainable environment.

Field Assessment of Neighboring Building and Tree Shading Effects on the 3D Radiant Environment and Human Thermal Comfort in Summer within Urban Settlements in Northeast China

Shading is one of the most effective strategies to mitigate urban local-scale heat stress during summer. Therefore, this study investigates the effects of shading caused by buildings and trees via exhaustive field measurement research on urban outdoor 3D radiant environment and human thermal comfort. We analyzed the characteristics of micrometeorology and human thermal comfort at shaded areas, and compared the difference between building and tree shading effects as well as that between shaded and sunlit sites. The results demonstrate that mean radiant temperature Tmrt (mean reduction values of 28.1°C for tree shading and 28.8°C for building shading) decreased considerably more than air temperature Ta (mean reduction values of 1.9°C for tree shading and 1.2°C for building shading) owing to shading; furthermore, the reduction effect of shading on UTCI synthesized the variation in the above two parameters. Within the shaded areas, short-wave radiant components (mean standardized values of 0.104 for tree shading and 0.087 for building shading) decreased considerably more than long-wave radiant components (mean standardized values of 0.848 for tree shading and 0.851 for building shading) owing to shading; the proportion of long-wave radiant flux densities absorbed by the reference standing person was high, leading to a relatively high long-wave mean radiant temperature, and R2 between long-wave mean radiant temperature and air temperature exceeded 0.8. Moreover, the directional sky view factor (SVF) was utilized in this study, and it showed significant positive correlation with short-wave radiant flux densities, but no statistically evident correlation with long-wave radiant flux densities. Meanwhile, Tmrt was most relevant with SVFS⟶ with R2 of 0.9756. Furthermore, UTCI rose two categories at the sunlit areas compared with that at the shaded areas. In contrast, Ta and Tmrt played the first positive role in UTCI at shaded and sunlit areas, respectively.

Outdoor thermal comfort improvements due to innovative solar awning solutions: An experimental campaign

Urban areas are increasingly affected by the Urban Heat Island (UHI) phenomenon, which is mainly due to highly dense urban environments and to solar and radiative properties of outdoor surfaces. UHI has a strong impact on urban microclimate, significantly contributing to the deterioration of outdoor human thermal comfort. Solutions based on high reflective materials in outdoor applications, e.g. solar awnings, could represent an important issue for mitigating UHI and improving pedestrians’ thermal comfort. For this purpose, the present research aims to investigate the effect of different radiative properties of solar awning textiles on microclimate and outdoor thermal comfort below them. High reflective materials are usually used for awning textile, but they are often characterized by high emissivity properties downward that may affect the pedestrians’ thermal comfort. The proposed solution consists in an awning textile with highly-reflective, highly-emissive properties upward and highly-reflective but low-emissive properties downward. Different solar awning configurations were tested by a microclimate experimental campaign on summer 2019. Outdoor thermal comfort under each awning was assessed by evaluating Physiological Equivalent Temperature (PET). Results show that a daily average PET reduction up to 2.5 °C is achieved thanks to the proposed solutions, proving benefits to pedestrians’ thermal comfort.

Thermal comfort of urban spaces using simulation tools exploring street orientation influence of on the outdoor thermal comfort: a case study of Jeddah, Saudi Arabia

AbstractAt present, the environmental quality of urban regions and outdoor spaces has turn out to be one of the main issues facing both climatologists and designers, which could be identified through their research outcomes. It is argued that the urban configuration affects the micro-climate of the urban outdoor spaces. The street’s orientation form was identified as an element, which impacts the urban environment with regards of receiving passive solar, solar radiation and reflection against urban absorption, wind flow and the possible urban cooling techniques. The key purpose of this study is to look into the urban configuration factors affecting the human thermal outdoor comfort in Jeddah city as an example of hot humid climate regions. To accomplish its aim, the research is divided to two sections. The first one illustrates the problem of the research, then generally reviews the literature associated with the outdoor human thermal comfort; in addition, it discusses the relationship between street orientation and micro-climate. The second section highlight the assessments carried out between four different orientations of urban streets from two different districts in Jeddah city, using ENVI-met software. The research adopts three environmental variables to be examined, namely air temperature, wind speed, relative humidity together with pedestrian thermal comfort as indicators for predicted mean vote, during summer and winter seasons. The outcomes of the comparison assist to identify decisions related street networks to achieve the desirable human outdoor thermal comfort in such an urban environment.