Architecture Department, Universitas Trisakti, Jakarta , Indonesia
*Corresponding Author : email@example.com
Abstract. Outdoorcomfort is important due to the public spaces functions. Open spaces provide thermalcomfort and a pleasant experience to improve the city life quality effectively. The influence of thermalcomfort in outdoor activities is a complex problem. This paper presents a literature review and discussion of aspects of physical, psychology, and social behaviour toward outdoorthermalcomfort. The valuation is determined not only by the “physical state” but also by the “state of mind”. The assessment is static and objective (i.e., physical and physiological characteristics) that it should be measured. Furthermore, an effective model to provide the knowledge of climatic conditions, as well as the dynamic and subjective aspects (i.e., psychological and social characteristics and behaviour), requires a comprehensive interview and observation. The model will be examined to describe the behaviour that is a reflection of perception and behaviour toward the environment. The adaptation process will constantly evolve so that it becomes a continuous cause between human behaviour and the spatial setting of the formation, which is eventually known as places and not just spaces. This evolutionary process is a civic art form.
Due to the increasing rate of urbanisation and population, the consequences resulting from heat impacts should be vital in order to obtain sustainable living. Climate change on outdoorthermal environment and UHI dominantly effect human health and well-being in a city. The increment in outdoor air temperatures also creates economic consequence, where UHI has clearly exemplified the environmental and economic impacts associated with a rise of ambient temperature. Apart from that, climate effects are negatively impacted by the UHI phenomenon, especially for people working outdoors. The outdoor environment is the most extreme and critical condition in investigating human thermalcomfort as it is exposed to the "double sun" phenomena, exposure from both direct sunlight and heat reflecting off the surrounding buildings. These issues can lead to social impacts if there is still lack of awareness and attention given to the thermal condition. The current study focused on the determination of thermalcomfort in selected areas, with several urban environmental parameters, i.e. street geometry, orientation, surface albedo and vegetation, and concentrated on using conventional methods for accessing heat stress. However, a knowledge gap still exists, which can be related to the impacts of thermalbehaviour on outdoor human thermalcomfort and heat stress in tropical climate, in terms of the effect of the built environment, land use and artificial construction materials. Little research can be found on the relationship between the impact of urban surface thermalbehaviour and outdoorthermalcomfort in Johor Bahru a city in Malaysia.
Abstract—The outdoorthermalcomfort is influenced by the perception and satisfaction of the pedestrians, especially in hot and arid climates. Accordingly, the researchers look for the appropriate methods to reduce the Urban Heat Island and thus to enhance the outdoorthermalcomfort level of pedestrians. However, there is limited research conducted on the outdoorthermalcomfort in hot and arid climate. This work is an investigation study conducted in an urbanarea (Haifa Street) in Baghdad city, characterized by an arid climate with very high temperatures in summer season reaching 50℃. This study focuses on investigating possible mitigation strategies to ensure how we could improve the thermalcomfort at pedestrian level for an urbanarea with intricate Western design (high–rise buildings, a large spacing between the buildings, asymmetrical canyon geometry, and lack of vegetation). We created four different scenarios to assess the role of vegetation elements such as trees, grass, and different shading patterns. The evaluation was performed in the hottest day in summer. For each scenario, the mean radiant temperature, specific humidity, air temperature, and wind speed distributions have been analyzed using ENVI-met software. Thermalcomfort is assessed using the PET thermal index (Physiological Equivalent Temperature) and Predicted Mean Vote (PMV). The results reveal that the PET index can be reduced to 10.4 ℃, the temperature can be decreased of about 2.4℃ and PMV to 3. The study shows how the urban factors such as the aspect ratio, vegetation cover, shadings, and geometry of the canyon are crucial elements that urban planners and municipalities have to take into account, especially for new urban developments.
In the field of urban climate, Givoni  underlined how urban design may impact on comfort through urban heat island phenomenon. In 1998, Givoni  has also showed some regression equation concerning outdoor temperature in urbanarea which may influence of comfort in outdoor space, unfortunately he has not proposed equation of thermalcomfort perception for outdoor at that time. Some of the researchers who focus on outdoorthermalcomfort, have proposed regression equations to estimate the scale of outdoorthermalcomfort, where the regression is functions of climate variables such are: solar radiation, air temperature, air humidity, wind speed, and radiant temperature, as shown in Table 1. In the table it appears that there is no study of outdoorcomfort scale models that are specifically intended for the case of humid tropical climates. Some other researchers have also proposed the temperature index to measure the level of comfort for people who are at particular climatic environment. The temperature index (in 0 C) is known as PET (Physiologically Effective Temperature) which is then used as the standard calculation of the thermalcomfort of outdoor space in Germany , out_SET (Outdoor Standard Effective Temperature), and TEP (Effective Temperature Psychologically) by . But again, the temperature index was also obtained through the data from field study conducted in the area where the environment is not humid tropical climates, so it remains to be evaluated for increase its precision when applied on a broader climate situation.
a building due to increased reflectance of solar radiation to building envelope, while the impact on heating demand is negligible.
2.2 Urban green
Vegetation affects outdoorthermalcomfort not only because of the different properties values (solar reflectance, infrared emissivity, heat capacity etc.) compared to other materials of the built environment, but also due to evapotranspiration procedure. Water loss (water vapor) increases air humidity which leads to an increase of latent cooling (Dimoudi & Nikolopoulou, 2003). Additionally, geometric characteristics of plants (height, tree crown width, leafage shape and density, etc.) determine shading in the urban environment and have a great influence on surface temperatures. For hot climates, shading is the basic factor that prevents the development of very high temperatures, because overheating is mainly caused by storage of heat to sun exposed surfaces (Ali Toudert, 2005). It has been observed that in an urban park the air temperature could be 3- 4°C lower than the surrounding urbanarea for the noon hours of a summer day (Bernatzky, 1982). Shashua-Bar & Hoffman (2000) have also investigated the cooling effect of shading in small urban green spaces, courtyards and streets in subtropical climate and detected an air temperature difference of 1°C compared to spaces exposed to solar radiation. This difference could reach 3°C for the hottest hours of the day. Regarding energy savings due to urban green, many studies indicate that the cooling effect of shading on building envelopes could conduce to the reduction of cooling demand (Akbari et al., 1997; McPherson et al., 1997; Donovan & Butry, 2009).
5 Simulation Process
ENVI -met has two basic steps before simulation is running. The first is ed- iting the input of the urbanarea to be tested. The second step is editing the configuration file, where the information about temperature, wind speed, humidity, and databases for soil types and vegetation are entered. The simu- lation is then processed using both input and configuration files. ENVI -met outputs binary files which have to be imported into the visualization pro- gram LEONARDO .
The fundamental equations for fluid motion have been known since the 19th century which can be solved using a number of numerical solutions (Blocken & Gualtieri, 2012, p. 1). These numerical solutions attempt to solve the fundamental equation. However, numerical solutions can be suited to different applications and involve different levels of computer intensity. For example, calculating wind around a building would use a different numerical solution than calculating air or fluid flow through a heating, ventilation, and air conditioning system. The numerical solutions required for calculating wind patterns in an urbanarea are classed as part of Environmental Fluid Mechanics (EFM). In EFM, the numerical solutions are attempting to solve turbulence flows, meaning that the flows (the wind) have irregular fluctuations with their magnitude and direction. There are three main numerical solutions for solving these turbulent flows, Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and Reynolds-Averaged Navier Stokes (RANS) (Blocken & Gualtieri, 2012, p. 3).
Key words: city squares, area usage, Physiologically Equivalent Temperature (PET), behavioural adaptation
Due to a rapidly growing global population more and more people need to live and work in cities. Therefore, the question of urbanthermalcomfort, i.e. which thermal conditions are the most comfortable and enjoyable in urban environments, becomes of even higher importance. The increasing number of cities transform the natural areas, and inhabitants unavoidably become subjects of the strain of the new environment such as noise, air pollution, accelerated lifestyle and last but not least thermal stress (Unger 1999). Since the ’green islands’ in settlements have significant positive effects on life quality, the role of human comfort investigations in these places grows permanently. These public areas provide not only an aesthetical and pleasant environment for the citizens, but also increase the duration of their outdoor activities (Nikolopoulou et al. 2001, 2003, Thorsson et al. 2004).
ii) U drugoj fazi koristi se komponenta Outdoor Solar Temperature Adjustor koja je takođe neophodna za računanje vrednosti UTCI indeksa i odnosi se na računanje prilagođene srednje temperature zračenja (engl. Solar Adjusted Mean Radiant Temperature - SAMRT). Ova komponenta sadrži deo sa ulaznim i izlaznim podacima (Slika 9). Za ulazne podatke neophodno je uključiti informacije iz komponente Weather data file o lokaciji područja (longitudu, latitudu i altitudu), difuznu i direktnu solarnu radijaciju, kao i temperaturu vazduha. Zatim, u okviru ove komponente neophodno je izvršiti podešavanje parametara koji podrazumevaju elemente koji se odnose na model tela čoveka za koga se računanje vrednosti UTCI indeksa vrši. Ti podaci podrazumevaju položaj tela, ugao rotacije tela, nivo odevenosti i lokaciju tela. Elementi izgrađenog okruženja koji svojom geometrijom utiču na ishod SAMRT temperature takođe su neophodni u procesu računanja. Zatim, refleksija parterne površine i period godine za koji se sprovodi analiza. Svaki od ovih parametara je detaljno objašnjen u daljem tekstu.
As heat waves are the first natural cause of mortality [5, 21-25], this research focuses on the impact of UHI on thermalcomfort of people in urban open spaces. During a two week heat wave in August 2003, 70,000 people passed away . Heat related mortality occurs when human body absorbs more heat than it dissipates. This is more serious for elderly and people with cardio-vascular problems who have weaker thermoregulatory body system . Several studies have shown strong correlations between heat waves and excess mortality [21, 23, 26]. In this way, making cities cooler seems vital for public health.
The Reynolds Averaged Navier Stokes (RANS) approach is a modeling method in which the major variables such as temperature and velocity are divided into time-averaged and turbulent fluctuation, and then the turbulent model is used to model the turbulent fluctuation (Nielsen et al., 2007). Blocken and Persoon (2009) used RANS in studying an urban setting to evaluate wind comfort on pedestrian level around a large football stadium to study the effects of adding new high-rise buildings in the surroundings. The advantages of RANS include its availability in all CFD codes, inexpensive and widely validated, but it is not as accurate as LES because of the lack of capturing smaller length scale (eddy scale) in RANS. Blocken et al. (2009) and He and Song (1999) indicated another shortfall of RANS, which is that RANS solves only the mean flow and small eddies, whereas the LES solves the large and most important turbulent eddies. Santiago et al. (2010) have used LES model and RANS model to evaluate the effect of the direction of incident wind on the flow plume dispersion. It was noticed that LES requires greater computational cost than RANS, and the use of RANS with turbulent kinetic energy (k- ɛ) model is reasonably suitable for simulating wind flow in urban environments, and has increasingly been used for wind studies at pedestrian level (e.g. Blocken et al., 2004; Yoshie et al., 2007; Blocken and Persoon, 2009). In LES model, large scale structures in turbulent flow are created directly, this is due to unsteadiness of the mean flow (shear or buoyancy effects) that are simulated directly as they are problem reliant, anisotropic and play a key part in transportation of mass, momentum and energy. LES modeling is most appropriate for the simulation of air pollutant, which is because of its ability to solve the large eddies in the field of the fluid flow (e.g. Walton et al., 2002). In contrast, small scale structures can be modeled in LES with less effect on the prediction value (Uddin, 2008). The grids in LES are more refined compared to RANS and hence need more computational power for simulation. The employment of LES in urban environment studies could be seen in Salim et al. (2011), Li et al. (2009), and Tominaga, et al. (2008). Researchers such as Tominaga et al. (2008) applied LES simulation to high-rise building geometry to study the wind flow around it within the surface boundary layer, flow within an urban complex and around a tree.
Vegetation is rare in this part of the city, except an urban square adjacent to City Hall building which is rich in greenery and is considered as an important urban park. Streets are paved with asphalt and there are concrete and brick paths on sides. Building facades are made of brick and stone in variety of colors and wit h 33 to 75% window to wall ratio . Masonry material with individual windows characterizes the buildings in western side of Main Street and the Canal District as Historic District while in Innovation District, including Washington Square, precast concrete, glass, and metal panels are preferred . Downtown Worcester is characterized by municipal buildings and it is the site of important business, cultural and civic activities . Diverse uses in addition to historic identity of this area make it a potentially livable and walkable urban community. Considering relatively high level of pedestrian users in downtown Worcester, it is necessary to study thermalcomfort at pedestrian level in this area. The study area represents different forms and geometric configurations of open spaces and streets. Study locations were chosen based on variation of the Sky View Factor (SVF), height to width (H/W) ratio and orientation and listed as following: 1- east-west canyon (Mechanic Street), 2- north-south canyon (Main Street), 3- urban square (City Common), and 4- surface parking (Fig. 2). Detailed description of study locations including major surface material, SVF, and H/W ratio are illustrated in Table 1.
The third section included open personal questions such as gender, height, weight, level of activity and type of clothing.
Essentially, the questionnaire questions were designed so that in a short period (10 minutes), pedestrians in the neighborhood of different age and gender groups could be interviewed to extract information about their level of perceived thermalcomfort (Figure 4). The total score from the questions is presented as an indicator of the perceived thermalcomfort (PTC). However, the inquiry of PTC was ambiguous for occupants, so this question was addressed by asking how comfortable do you feel in terms of temperature (not too hot not too cold)? For the second inquiry, the question that was also directly asked was how much heat do you feel? Therefore, data relevant to this question was considered in reverse form to determine the perceived thermalcomfort index (very high = 1 to very low = 5). It should be noted that in order to accurately derive the research data, prior to the start of summer on 22 May, 18 experimental micro-climatic data and questionnaires (six questionnaires at each intersection) were compiled (10 minutes at each intersection) in order to address the issues and queries of questionnaire gaps and to identify bio-climatic notions amidst the main questionnaire compilation stage.
practice, these models are to be supported by both human-biometeorological and physiological information. The indexes were originally dependant on the energy fluxes between the human body and the environment. The Predicted Mean Vote Index (PMV), Effective Temperature (ET in °C), and Standard Effective Temperature (SET* in °C) (Fanger, 1982; Gagge, Fobelets, & Berglund, 1986); are examples of indexes originally developed for indoor thermalcomfort studies and were later adapted to be applied in outdoor settings (Cheng et al., 2012; Nikolopoulou et al., 2001; S Thorsson et al., 2004). The Outdoor Standard Effective Temperature (OUT_SET* in °C) (Spagnolo & de-Dear, 2003) and the Physiological Equivalent Temperature (PET in °C) (Mayer & Höppe, 1987) are thermo- physiological assessment variables that were purposely designed for outdoor settings. PET is the most predominant thermalcomfort index used in the OTC studies (da Silveira Hirashima et al., 2016; Elnabawi, Hamza, & Dudek, 2016; Holst & Mayer, 2011; Kántor, Égerházi, et al., 2012; Lee et al., 2013; Lee & Mayer, 2018; Lee, Mayer, & Chen, 2016; Lee, Mayer, & Schindler, 2014; Lin & Matzarakis, 2008; Lin, 2009; Liu et al., 2016; Mayer et al., 2008; Ng & Cheng, 2012; Salata et al., 2016; Yang, Wong, & Zhang, 2013).
The way of designing urban fabric, has a major effect on reducing the temperature of open space and can be used in a manner that enables users to use space in a permanent and convenient way. Thus, the relationship between the qualitative and quantitative effects of various parameters should be considered based on the orientation of the streets and time. Design and development of the urban environment requires the application of its components for improving the performance of elements that can be either the buildings and their orientation and shape, or the smaller objects in micro level such as trees, water and floor coverings. Tehran has three urban fabrics including open spaces, high-rise buildings and urban intense fabric that each one has their own optimum performance in thermalcomfort. Since the street acts as a linear urban spaces and the main connector of noted texture, thermalcomfort is very important for its users. Micro scale design for pedestrians to benefit from the sufficient wind and temperature is equally effective as the height of masses, location and orientation of buildings to lead the wind flows and receive adequate radiation in an urban site. The main question is what is the role of these elements in a linear open space design? Some of the urban landscape features such as the trees and water features (stream in streets) and sidewalks floorings have an influence in the amount of solar energy and wind flow in different ways and they can be useful in helping energy efficiency. 2.1. Methods
This paper explores the effect of outdoor microclimatic environment upon indoor conditions for different urban block types in hot-humid climate. The main focus here is on courtyard patterns, considering its potentials for hot-humid climate is not fully understood yet. Courtyard spaces have been examined in conjunction with the internal spaces of surrounding buildings with the aim to create a link between both. Based on theoretical models, it intends to devise strategies to optimise both indoor-outdoorthermalcomfort and building energy performance while enabling the building designers and urban professionals to consider these essential issues at the early design stage. For this study, four simplified archetypal urban arrays are selected, primarily developed by Martin and March. These are: pavilions, enclosed courtyard pavilions, open-square and open-rectangular courtyard pavilions. Firstly, it has observed the microclimatic characteristics of the geometric patterns through a high resolution CFD microclimatic model: ENVI-met. Thermalcomfort in the adjacent and enclosed outdoor spaces was assessed against Physiological Equivalent Temperature (PET) index with the aid of Rayman 1.2. Secondly, the energy performance of the surrounding buildings was analysed by IES-VE: a building performance modelling tool. The methodology and results from the current study can be integrated in the future urban planning processes in a high-density warm-humid context.
In this study, two thermalcomfort indices are employed to investigate outdoor human thermalcomfort within three major cities of different climates in Egypt. The indices are: the Discomfort Index (DI), and the Robaa Index (RI). The three considered cities are: Alexandria which is located in the north of Egypt, Cairo which is located in the middle and Aswan city which is located in the south of Egypt. The estimations of the two indices are based on the mean wind data of the three ci- ties, which covers the period from January 2010 to January 2011. The study results show that the thermalcomfort indices values can be employed to evaluate climate differences in urban areas. The calculated indices showed that; although extreme climate conditions are not reached in Egypt in general, the climate in the north is milder than in the south. In addition, the study results show that the RI is more practical than DI in assessing the human thermalcomfort in the outdoor envi- ronment.
Among the urban design elements, archetypal urban form, density, and geometry have important implications in matters of urban planning, such as built potential, daylighting, passive cooling potential, and walkability. The sustainable performance of urban systems is measured upon these and many other factors. The question of which urban design performs best cannot have an absolute answer. When a large number of variables are taken into account, it is likely that conflicts will emerge amongst them; terms such as “best” and “optimal” will certainly embody value judgments. One thing that is certain, however, is the need to understand the principles and dynamics that govern such variables. Only then can the entirety of their implications –and potential benefits- be used for the betterment of the society around them.