Outdoor Thermal Comfort Index Research Articles

ASSESSMENT OF OUTDOOR THERMAL COMFORT IN HOT ARID ZONE

The globe witnessed a rapid development of the concepts of sustainability, smart architecture, and intelligent buildings during recent decades. The Healthy environment, particularly thermal comfort, is an essential concern for planners, urbanists, and architects to produce a healthy and thermally comfortable environment. A better understanding of the parameters that affect the Outdoor Thermal Comfort (OTC) will enable urbanists and environmentalists to control the microclimate and to enhance environmental performance. Several parameters affect the thermal comfort of human-being such as air temperature, mean radiant temperature (MRT), air velocity, humidity, metabolic rate, and clothing insulation. Assessing the MRT is considered the most challenging parameter in outdoor spaces. Recent researches recognized several approaches to determine the OTC in different climatic zones. The influence of different climates and user groups has significantly altered the range of responses for thermal comfort. This paper focuses on reviewing the current state of knowledge on how to assess the OTC and the MRT in the hot arid climate. Results confirmed the integration of the appropriate OTC index with other design tools to evaluate the OTC and the MRT. It also confirmed that Physiological Equivalent Temperature (PET) and Predictive Mean Vote (PMV) are the most common indices. While ENVI-met and RayMan are the most common software to assess the OTC.

Outdoor Thermal Comfort Improvement of Campus Public Space

This study focuses on the design of a campus public space, located within the Faculty of Engineering, Chiang Mai University, Thailand. This area faces extreme temperatures, creating uncomfortable outdoor thermal conditions and hindering activities that are expected to support the learning and social cohesion needs of students. To create the best conditions in this space, three design alternatives such as adding a pond, large trees, or shrubs were considered, and the Physiologically Equivalent Temperature (PET) was used to calculate the outdoor thermal comfort index for each alternative. The alternatives were then compared to the base case. The PET can be calculated using the ENVI-met simulation software following the appropriate field data collection and calibration process. The results showed that adding large trees in the south-west area is the best design alternative. The PET for this alternative was 3.17 % lower than the base case. In addition, this design workflow is an effective working model for further outdoor public space designs to meet the constraints of effective sustainable development in any tropical campus area.

Assessing the Impact of Urbanization on Outdoor Thermal Comfort in Selected Local Government Areas in Ogun State, Nigeria

This study seeks to assess the land use land cover (LULC) and spatial-temporal trends of six outdoor thermal comfort indices in four Local Government Areas (LGAs) of Ogun state, Southwestern, Nigeria. Data used for this study are air temperature, relative humidity, cloud cover and wind speed which span from 1982 to 2018. These data were obtained from ERA-INTERIM archive. The 1986, 2000 and 2018 used for the analysis of the LULC were from the satellite imagery hosted by the United States Geological Survey (USGS). Landsat Thematic Mapper, Landsat 7 and Landsat 8 Operational Land Imager data of 1986, 2000 and 2018 to assess the changes that have taken place between these periods. Thermal comfort indices such as Effective Temperature (ET), Temperature Humidity Index (THI), Mean radiant temperature (MRT) and Relative Strain Index (RSI) were used. Rayman model was used for the computation of the three thermal comfort indices (MRT, PET, PMV). The results show decrease in vegetation, forest, and an increase in percentage of built-up areas between 1986–2000, and 2000–2018. A rapid increase in built-up areas in the three (Abeokuta South, Ifo, Shagamu,) of the four LGAs, while one (Ijebu East) has a slow increase in the built-up areas. The trend in the thermal comfort indices also shows that thermal discomfort had been on increase for the past 37 years and it was observed that the level of comfort has deteriorated more in the last decade compared to the previous decade especially in the built-up areas. This work suggests a framework for evaluating the relationship between the quantitative and qualitative parameters linking the microclimatic environment with subjective thermal assessment. This will contribute to the development of thermal comfort standards for outdoor urban settings. Also, the study will help urban planners in their decision making, and in heat forecast.

Outdoor thermal comfort acceptability calibration: A calibration of the PET outdoor thermal comfort index in Singapore: does comfort vary respect to land uses?

Outdoor thermal comfort acceptability calibration: A calibration of the PET outdoor thermal comfort index in Singapore: does comfort vary respect to land uses?

Understanding volume and correlations of automated walk count: Predictors for necessary, optional, and social activities in Dilworth Park

In this paper, we explore the potential use of automated pedestrian walk count data in urban design research. The Center City District (CCD) research group used computer vision to collect automated pedestrian walk data from Dilworth Park, Philadelphia. By comparing the count data and participant observations of social activities in the park, we found that the frequencies of social activities in the park could be predicted by the pedestrian count when considering the outdoor thermal comfort index and the types of events taking place in Dilworth Park. By examining correlations among multiple sensors, we found that the entry–exit correlation is a useful indicator to assess how people use public space by estimating the ratio of necessary-to-optional activities.

Potential of neuro-fuzzy methodology for forecasting of outdoor thermal comfort index at urban open spaces

Thermal comfort in open urban areas could influence medical, sociological, environmental and economic parameters. Therefore there is need to establish good thermal comfort in the areas to maintain the parameters at acceptable levels. Since the thermal comfort is variable, there is need to determine which parameters has the most impact on the thermal comfort variations. Hence in this article an attempt was made to rank parameters based on their influence on the thermal comfort. Prediction of thermal comfort was performed based on the parameters' ranking models. Physiological equivalent temperature (PET) was used as the thermal comfort indicator. Air temperature, vapor pressure, wind speed, irradiance are the inputs which are used in the investigation among others. Neuro-fuzzy methodology was used for the PET analyzing. Obtained results could have practical advantage for urban planners and designers to make the best thermal comfort for visitors in open urban areas.

Identifying solar access effects on visitors' behavior in outdoor resting areas in a subtropical location: a case study in Japan Square in Curitiba, Brazil.

Changes in microclimate due to urban morphology tend to directly affect outdoor thermal comfort, thereby influencing people's behavior. In order to investigate that, this study analyzed preferences for specific resting areas within an urban square surrounded by high-rise buildings in a subtropical location. In order to understand behavioral adaptations as regards sunlight availability (direct or reflected) or shaded situations (partly, fully) in resting areas, the analysis was conducted according to an observational method during the four seasons of 2016. Two high-definition cameras with time-lapse function were positioned at vantage points facing distinct benches, shooting at intervals of 1.5min between scenes. Altogether, 86,561 scenes were analyzed. As a thermal comfort parameter, the outdoor thermal comfort index 'PET' (physiological equivalent temperature) was used, by post-processing meteorological data from the local meteorological station. The availability of situations (sun-lit, shaded-partly or fully, reflected sunlight) in each frame and per bench and the preference of visitors for such areas were considered in the analysis. During winter, there was a prevalence of shaded situations, mostly due to adjacent buildings. In summer, the most common condition was partly shaded by trees. The choice for a given resting condition was found to be closely related to PET index values and thermal comfort/stress classes and less so to seasonal changes.

Investigation into the differences among several outdoor thermal comfort indices against field survey in subtropics

Comfortable and healthy outdoor microclimates are beneficial to sustainable urban development. Based on a comprehensive comparison of some currently frequently used thermal comfort indices, including PMV, WBGT, PET, SET*, and UTCI, the differences among these indices are significant in dealing with the fundamental energy balance model, descriptive equations, and application boundary conditions. In order to validate these indices, a subjective questionnaire survey with field measurements was carried out on a university campus in Guangzhou in southern China. Results revealed strong linear relationships between operative temperature and mean radiant temperature (Tmrt), WBGT, PET, SET*, UTCI, as well as PMV. However, the relationships between these thermal comfort indices and the mean thermal sensation vote (MTSV) are not clear for a hot outdoor environment, especially when the operative temperature was above 34 °C. The ranges of the heat stress category and PMV need to be modified for the evaluation of hot outdoor environments.

Passive activity observation (PAO) method to estimate outdoor thermal adaptation in public space: case studies in Australian cities.

Outdoor thermal comfort is influenced by people's climate expectations, perceptions and adaptation capacity. Varied individual response to comfortable or stressful thermal environments results in a deviation between actual outdoor thermal activity choices and those predicted by thermal comfort indices. This paper presents a passive activity observation (PAO) method for estimating contextual limits of outdoor thermal adaptation. The PAO method determines which thermal environment result in statistically meaningful changes may occur in outdoor activity patterns, and it estimates thresholds of outdoor thermal neutrality and limits of thermal adaptation in public space based on activity observation and microclimate field measurement. Applications of the PAO method have been demonstrated in Adelaide, Melbourne and Sydney, where outdoor activities were analysed against outdoor thermal comfort indices between 2013 and 2014. Adjusted apparent temperature (aAT), adaptive predicted mean vote (aPMV), outdoor standard effective temperature (OUT_SET), physiological equivalent temperature (PET) and universal thermal comfort index (UTCI) are calculated from the PAO data. Using the PAO method, the high threshold of outdoor thermal neutrality was observed between 24°C for optional activities and 34°C for necessary activities (UTCI scale). Meanwhile, the ultimate limit of thermal adaptation in uncontrolled public spaces is estimated to be between 28°C for social activities and 48°C for necessary activities. Normalised results indicate that city-wide high thresholds for outdoor thermal neutrality vary from 25°C in Melbourne to 26°C in Sydney and 30°C in Adelaide. The PAO method is a relatively fast and localised method for measuring limits of outdoor thermal adaptation and effectively informs urban design and policy making in the context of climate change.

The impact of increasing urban surface albedo on outdoor summer thermal comfort within a university campus

The impact of increasing urban surface albedo on outdoor thermal comfort was studied in two phases:Firstly, the thermal conditions of three locations with different ground surface materials were compared. The study used CFD modelling followed by a measurement campaign to validate the control simulation. It was observed that the physiological equivalent temperature (PET as the outdoor thermal comfort index) in the campus park (covered with grass) was 11.0 °C lower than the parking lot (paved with concrete) at 16:00 CET.As the next step, the albedo of the roofs and walls were increased from 0.2 (control) to 0.3, 0.4, 0.5 and 0.6. It was found that increasing the albedo made the open space of the courtyard uncomfortable due to the higher reflectivity of high-albedo materials. An increase of every 0.1 albedo of the surfaces led to 1.2 °C higher mean radiant temperature, and consequently, 0.8 °C higher PET. The study also showed that the increase of albedo radiated more sun to the ground surface. This increased average ground surface sensible heat flux (6.7 W/m2) and surface temperature (0.4 °C) during the day. This finding shows that the position and orientation of high albedo materials can significantly affect pedestrians' thermal comfort in urban open spaces.

Investigation into sensitivities of factors in outdoor thermal comfort indices

With the development of the urban city, increasing attention has been paid to outdoor thermal comfort. In this paper, an analysis of the sensitivities of different factors, including the personal factors and physical parameters of the thermal environment was conducted. The results showed that there was a strong linear relationship between the Physiological Equivalent Temperature (PET) and operation temperature. When the operation temperature was lower than 32 °C, the effect of air velocity on the PET was positive. However, the effects of other factors, including relative humidity, clothing insulation, and metabolic rate, on the PET were insignificant. An exponential relationship was found between the UTCI and the operation temperature. The effect of air velocity change on the UTCI became weaker and weaker with the increase of operation temperature. Compared with the PET, the linear relationship between the UTCI and relative humidity was clearer. A field survey of thermal comfort carried out in Guangzhou University was used for the validation of the thermal comfort models. It was observed that the clothing insulation requirement increased with the decrease of air temperature in autumn. The variations in metabolic rate were also obvious, from 1met to 3.8 met. More than 70% of the people had been walking before they arrived at the survey locations. In addition, there were some differences in the neutral PET and UTCI temperature between the metabolic rates of 1.0–2.0 met and of 2.6 met. Meanwhile, models of MTSV against the PET and UTCI under different metabolic rates were established.

Thermal Perception in the Mediterranean Area: Comparing the Mediterranean Outdoor Comfort Index (MOCI) to Other Outdoor Thermal Comfort Indices

Outdoor thermal comfort is an essential factor of people’s everyday life and deeply affects the habitability of outdoor spaces. However the indices used for its evaluation were usually developed for indoor environments assuming still air conditions and absence of solar radiation and were only later adapted to outdoor spaces. For this reason, in a previous study the Mediterranean Outdoor Comfort Index (MOCI) was developed, which is an empirical index able to estimate the thermal perception of people living in the Mediterranean area. In this study it was compared numerically (by using the data obtained through a field survey) with other selected thermal indices. This comparison, performed in terms of Spearman’s rho correlation coefficient, association Gamma, percentage of correct predictions and cross-tabulation analysis, led to identify the MOCI as the most suitable index to examine outdoor thermal comfort in the interested area. As a matter of fact it showed a total percentage of correct predictions of 35.5%. Good performances were reported even in thermophysiological indices as the Physiological Equivalent Temperature (PET) and Predicted Mean Vote (PMV). Moreover it was revealed that adaptation and acclimatization phenomena tend to have a certain influence as well.

Forecasting of outdoor thermal comfort index in urban open spaces: The Nis fortress case study

Outdoor thermal environment is affected by variables like air temperature, wind velocity, humidity, temperature of the radiant surfaces, and solar radiation, which can be expressed by a single number - the thermal index. Since these variables are subject to annual and diurnal variations, prediction of thermal comfort is of special importance for people to plan their outdoor activities. The purpose of this research was to develop and apply the extreme learning machine for forecasting physiological equivalent temperature values. The results of the extreme learning machine model were compared with genetic programming and artificial neural network. The reliability of the computational models was accessed based on simulation results and using several statistical indicators. According to obtained results, it can be concluded that extreme learning machine can be utilized effectively in short term forecasting of physiological equivalent temperature.

Implications of Building Material Choice on Outdoor Microclimate for Sustainable Built Environment

The climatic conditions in a man-made urban environment may differ appreciably from those in the surrounding natural or rural environs.... each urban man-made buildings, roads, parking area, factories......creates around and above it a modified climate with which it interacts [1].Outdoor thermal comfort has gained importance in thermal comfort studies especially in tropical countries. In country like India, culturally the activities are spread both indoors and outdoors. Therefore the need for ambient outdoor environment gains importance. As there are many factors that contribute to outdoor thermal comfort (climatic factors and physical factors), this study aims in analyzing the impact of building material contribution, in an institutional courtyard. In order to understand the thermal contribution of various building materials and to suggest material choice to designers, ENVIMET is used for simulation purpose. The outdoor thermal comfort index employed in this study is PET (Physiological Equivalent Temperature), calibrated using RAYMAN.