Assessment of The Effect of Material Type Used in Urban Surfaces on Heat Island Potential

ARCHITECTURAL SCIENCES AND SUSTAINABLE APPROACHES: URBAN RESILIENCE Editors Prof. Dr. Ömer ATABEYOĞLU Prof. Dr. Ertan DÜZGÜNEŞ October 15, 2025 Copyright © 2025 by İKSAD publishing house All rights reserved. No part of this publication may be reproduced, distributed or transmitted in any form or by any means, including photocopying, recording or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law. Institution of Economic Development and Social Researches (The Licence Number of Publicator: 2014/31220) TÜRKİYE TR: +90 342 606 06 75 USA: +1 631 685 0 853 E mail: [email protected] www.iksadyayinevi.com It is responsibility of the author to abide by the publishing ethics rules. Iksad Publications – 2025© Architectural Sciences and Sustainable Approaches: Urban Resilience ISBN: 978-625-378-337-2 Cover Design: Prof. Dr. Ertan DÜZGÜNEŞ October 15, 2025 Ankara / Türkiye Size = 16x24 cm PREFACE Dear Professors and Colleagues, We are pleased bring to life that Architectural Sciences and Sustainable Approaches: Urban Resilience, which was published as an e-book by IKSAD Publishing House with the editors Prof. Dr. Ömer ATABEYOĞLU and Prof. Dr. Ertan DÜZGÜNEŞ. This book project, entitled “Architectural Sciences and Sustainable Approaches: Urban Resilience,” aims to address sustainability-oriented approaches to urban resilience from theoretical, methodological, and practical perspectives. The volume seeks to establish a multi-layered platform of discussion, ranging from the scale of individual buildings to the entirety of the urban fabric. Within this framework, it welcomes contributions from scholars and researchers working in architecture, urban design, landscape architecture, urban and regional planning, environmental engineering, and related disciplines. With the valuable contributions of our chapter authors working in the professional disciplines of landscape architecture, architecture, city and regional planning, urban design and sustainability, we have completed Architectural Sciences and Sustainable Approaches: Urban Resilience book study has been completed with 24 book chapters. We would like to thank you, our esteemed authors, for their contributions to the preparation of the book. We would also like to thank the editorial board and IKSAD Publishing House. We wish to continue this process we have started in the coming years. In addition, we would like to express our sincere appreciation to Prof. Dr. Atila GÜL, the book coordinator of IKSAD Publishing House, for his guidance and support throughout the publication process. We hope that our book ‘Architectural Sciences and Sustainable Approaches: Urban Resilience’ will be helpful to the readers. Best regards. 15.10.2025 EDITORS Prof. Dr. Ömer ATABEYOĞLU Prof. Dr. Ertan DÜZGÜNEŞ EDITORS Prof. Dr. Ömer ATABEYOĞLU Prof. Dr. Ertan DÜZGÜNEŞ AUTHORS The authors were listed in alphabetical order Alper ÇABUK Ayça GÜLTEN Ayşe ÖZYETGİN ALTUN Ayşe Özge ŞİMŞEK SOYSAL Ayşegül TANRIVERDİ KAYA Demet EROL Deniz DEMİRARSLAN Ebru Vesile ÖCALIR Eda ŞENTÜRK Elif Kübra ÖZTÜRK Emine BAYDAN Esra KESKİN Feran AŞUR Feyza Sena ŞENOCAK Filiz KARAKUŞ Furkan AKDEMİR Gencay ÇUBUK Gülşah BİLGE ÖZTÜRK Halil DUYMUŞ Hamza ALTAŞ Hande AKARCA İnci OLGUN Kemal Mert ÇUBUKÇU Kumru ÇILGIN Mehmet Akif IRMAK Mehmet Emin DAŞ Mehtap ÖZENEN KAVLAK Merve ALICI AKA Mesut GÜZEL Muhammed Akif AÇIKGÖZ Muhammed Emir GÖRAL Murat YEŞİL Olcay Türkan YURDUGÜZEL Özge DÜZGÜN EREKİNCİ Pervin YEŞİL Rabia Nurefsan ACIKGOZ Sedef ŞENDOĞDU Seher Simay KUŞOĞLU Serim DİNÇ Sevilay YILDIZ Sinem SEYHAN Şevval ERGİNDOĞAN Şuheda ALTUNOK Temuçin Göktürk SEYHAN Tuba Nur OLĞUN Tuna BATUHAN Ufuk Teoman AKSOY Yusuf Eminoğlu REVIEWER LIST The authors were listed in alphabetical order Aslıhan TIRNAKÇI Nevşehir Hacı Bektaş Veli University Atila GÜL Süleyman Demirel University Ayşe Kalaycı ÖNAÇ İzmir Katip Çelebi University Bige ŞİMŞEK İLHAN İstanbul Medipol University Burcu YILMAZEL Eskişehir Technical University Eda KOÇAK Siirt University Ekrem BAHADIR Ankara Yıldırım Beyazıt University Elif KUTAY KARAÇOR İstanbul Technical University Hakan ARSLAN Ondokuz Mayıs University Hilal TURGUT Karadeniz Technical University Meliha AKLIBAŞINDA Nevşehir Hacı Bektaş Veli University Murat AKTEN Süleyman Demirel University Nihan Sümeyye GÜNDOĞDU Atlas University Okan Murat DEDE Amasya University Ömer Lütfü ÇORBACI Recep Tayyip Erdoğan University Selcen Nur Erikci Çelik Beykoz University Sibel AKTEN Isparta Unıversıty Of Applıed Scıences Sinem ÖZDEDE Pamukkale University Şeyma ŞENGÜR Ordu University Turgut KALAY Kütahya Dumlupınar University Tendü Hilal GÖKTUĞ Aydın Adnan Menderes University 288 1. Introduction Urbanization and industrialization, while improving the quality of human life, also bring several problems such as global warming, industrial waste, and air pollution. In addition to the negative impacts of these issues on a global scale, urban areas characterized by industrial interaction and the use of synthetic construction materials are also affected. Consequently, the natural environment and ecosystem are adversely impacted, leading to an ecological imbalance (Rizwan &Dennis, 2008). One of the most significant local-scale changes caused by urbanization is its impact on climatic elements. To analyze these changes effectively, it is essential first to understand the concept of the Urban Heat Island (UHI). When discussing urban climate, temperature is the primary element to be examined. It has been a well-established fact for over a century that metropolitan areas are warmer than rural areas (Gulten & Oztop, 2020) In contemporary urban environments, green spaces have been mainly replaced by tall buildings and various urban elements such as streets, avenues, and sidewalks. The use of motor vehicles, heat emissions resulting from industrialization, and human activities that directly release heat contribute to urban warming. Moreover, surfaces such as concrete pavements, asphalt roads, and buildings constructed with materials like concrete, brick, and cinder blocks absorb solar radiation during the day. This stored energy is subsequently released into the atmosphere as longwave thermal radiation during the night, leading to an increase in nighttime air temperatures. This phenomenon is known as the Urban Heat Island (UHI) effect (Kum, 2006). 289 Although the UHI effect is typically observed at night, it is fundamentally the result of energy absorption during the daytime and its delayed release. Therefore, the amount of solar energy absorbed during the day, along with the physical and thermophysical properties of the urban environment, plays a crucial role in the formation and intensity of the UHI effect (Givoni, 1998). At this point, the extent to which different types of materials used on urban surfaces (such as asphalt, concrete, stone, and permeable surfaces) affect the heat island effect emerges as an important research question. This study aims to investigate the role of different material types used in urban surfaces, such as roofs, building facades, pavements, and streets, on the heat island potential and to compare these materials in terms of their thermal properties. The effects of different materials on Heat Island Potential (HIP) are examined by Computatioanl Fluid Dynamics (CFD) simulations. It identifies which materials are more advantageous for reducing HIP in horizontal and vertical urban elements, and how the right material for each urban element affects HIP. 1.1. Formation of the Urban Heat Island In urban areas, the temperature increase caused by human necessities leads to the upward movement of atmospheric particles through convective processes. As altitude increases and air temperatures decrease, these particles encounter colder air masses, resulting in a horizontal displacement toward the urban periphery. In these boundary regions, the particles tend to subside (Figure 1). 290 Figure 1. Urban heat island mechanism (Kum, 2006) As a result, an urban heat island and a “dust dome” are formed, characterized by higher intensity at the city center and decreasing intensity toward the periphery (Göksu, 1993). The particles constituting the heat dome are transported upward from the source area by rising warm air and tend to accumulate most densely in the urban core. The thickness and impact of the heat island vary depending on the anthropogenic heat sources and the physical characteristics of the city (Figure 2). Figure 2. Urban heat island profile varies according to different residential areas (EPA,2008) This effect becomes particularly pronounced during nights with clear skies. The urban heat island phenomenon is most clearly observed when 291 comparing urban temperatures with those of surrounding rural areas. The primary reason for this discrepancy lies in the differing thermal storage capacities of surface materials in urban and rural settings. In addition, heating of residential buildings and the release of waste heat from fossil fuel use in urban areas contribute to this effect. Based on the main factors affecting urban climate, the causes of urban heat island formation can be summarized as follows (Kum 2006; Moonen et al 2012): • Urban surfaces and building materials with high solar absorption capacity, • Impermeable surfaces that prevent infiltration and cause rainwater to be diverted through drainage systems, • Urban geometry and building height reducing wind speed and air circulation, • Limited green spaces that reduce evapotranspiration, leading to increased energy retention, • Decreased advection and convection along with temperature inversion, • Heat emissions from vehicles, heating systems, and industrial activities, • Use of low-quality fossil fuels resulting in incomplete combustion and increased waste heat release. 1.2. The Impact of Urban Heat Island on Climatic Elements The impact of materials used in urban areas on the heat island is directly related to climatic elements. Factors such as the amount of radiation acting on a surface, its relationship with wind, or humidity and precipitation rates 292 can alter material behavior and, consequently, the heat island effect. Therefore, this section briefly describes the relationship between the urban heat island and climatic elements. Climatic elements in cities differ from rural areas due to the urban heat island effect. Table 1 shows the differences in the main climate elements. The effects of the urban heat island on the climate elements are also explained. Table 1. Main Climate Elements Climatic Element Parameter Urban Area (Compared to Rural) Temperature Annual average +0.7% Winter maximum +1.5% During cold season +2% to -3% Wind Speed Annual average -20% to -30% Extreme wind -10% to -20% Calm conditions variation +5% to +20% Humidity Annual relative humidity -6% Average (winter) -2% Seasonal (summer) +8% Cloudiness Total cloud cover +5% to +10% Fog +100% (winter), +30% (summer) Precipitation Total +5% to +10% Number of rainy days +10% Number of snowy days -4% Urban temperature increases are typically more pronounced toward city centers, where building density and, consequently, population concentration are higher. Although thermal variations may show irregularities due to urban morphology and construction intensity, the general trends in temperature fluctuations within cities—both rising and falling—are distinguishable. Major metropolitan areas can generate their own microclimatic conditions, largely independent of their surroundings (Moonen et al, 2012). 293 The most significant urban temperature increases are usually observed in the average minimum temperatures. For instance, the central area of London records an average minimum temperature approximately 2 °C higher than that of the surrounding rural zones. Nevertheless, because the shape and intensity of the urban heat island vary considerably depending on time and location, relying solely on average values may result in an inaccurate representation of thermal dynamics (Kum, 2006). In Turkey, which is located in the mid-latitudes, the Urban Heat Island (UHI) effect can have a beneficial aspect by contributing to milder winter conditions in urban centers. However, during the summer months, increased solar radiation combined with the influence of hot air masses affecting the region exacerbates thermal discomfort and the prevalence of heat-related health issues in cities (Memon, Leung &Chunho, 2008) All surfaces on Earth gain heat through incoming solar radiation (shortwave) and lose heat by emitting longwave radiation back into the atmosphere. On dry surfaces, solar radiation absorbed during the day is converted into sensible heat, leading to an increase in surface temperature. Conversely, solar energy absorbed by vegetated or moist surfaces is transformed into latent heat through evapotranspiration, resulting in a relatively lower rise in surface temperature. The emission of longwave radiation, which facilitates cooling, is a continuous process occurring both day and night (Givoni, 1998). A portion of the incoming solar radiation is absorbed by the surface and converted into either sensible or latent heat, while another portion is reflected back into the sky, having no direct effect on surface temperature. Although urban and rural areas with similar geographical conditions 294 receive approximately the same amount of solar radiation, urban areas may experience reduced radiation due to air pollution. In such cases, a portion of the incoming radiation is either absorbed or reflected by the urban atmosphere, particularly under polluted conditions. This phenomenon is quantified using the extinction coefficient (α, 1/m), which describes the atmosphere’s absorptive capacity (Reiss et al., 2007). In densely built urban environments, the path of solar radiation to building surfaces becomes increasingly complex. A significant amount of radiation strikes rooftops, some reaches vertical surfaces such as walls, and only a small fraction reaches the ground. Especially in areas with tall buildings and narrow spaces, minimal radiation reaches the surface. The radiation that reaches wall surfaces is partly reflected and partly absorbed. Reflected radiation often strikes adjacent buildings, initiating a continuous series of inter-reflections among urban surfaces. Only a minor portion escapes into the atmosphere, while the majority is absorbed by building facades and later released as longwave radiation during evening and nighttime hours. Urban elements, such as walls, streets, and pavements, emit longwave radiation into the sky. However, the magnitude of this heat loss is closely tied to the surface’s ability to "see" the sky. For instance, a wall in an open environment can view only half of the sky dome, resulting in significantly reduced radiation emission compared to a horizontal roof. Consequently, the longwave radiation emitted by a wall is typically about half of that emitted by a roof surface. In urban settings where buildings are of similar height, rooftop heat loss can be considered comparable to that of rural areas. However, when building heights vary, taller buildings absorb the longwave radiation 295 emitted by shorter rooftops, thereby decreasing overall heat loss within the urban canopy—the volume between the ground surface and rooftop level. In conclusion, urban areas experience more intense warming compared to their rural counterparts due to the thermal effects resulting from the absorption of solar energy and the physical characteristics of the built environment (Givoni,1998). In urban areas, wind effects, particularly at ground levels, have a direct impact on the amount of energy consumed for heating and cooling, on human health and comfort, and on the formation of air pollutants. During periods of rising average temperature, increasing wind speed reduces the stress that hot weather creates on people, and the urban heat island effect decreases as wind speed increases (Givoni,1998). In urban environments, tall buildings, due to their height, distance, and orientation, significantly impact the wind speed and direction. A portion of the wind striking a tall building is directed downward in the forward direction, causing undesirable wind circulation and increased speed near the surface. Another portion of the wind drifts toward the edges of the building, resulting in increased wind speeds in these areas. Wind speed decreases at the rear of the tall building. As the building height increases, the amount of calm area at the rear increases (Kural, 2007). 2. Material and Method In the study, an area in the Elazığ city has been chosen and some simulations have been performed by Ansys Fluent, which is a CFD-based program. Results obtained from simulations were evaluated over a parameter called Heat Island Potential (HIP). 296 2.1. Heat Island Potential The concept of heat island potential was first introduced in a study conducted by Akinoru Lino and Akira Hoyano (1996). Defined in the study, "Development of a Method to Predict the Heat Island Potential Using Remote Sensing and GIS Data," heat island potential is a parameter that examines surface temperature distributions and the urban thermal environment in urban areas based on sensible heat flux. Sensible heat flux is a convenient index that allows estimating the effects of the atmosphere on the urban canopy and can indicate how air temperature affects a metropolitan area. The sensible heat flux for a given area can be defined by the formula given below; 𝑄 = ∑ 𝛼𝑐𝑇𝑦−(𝑇𝑠+𝑇𝑎)𝑑𝑦 𝐴 (1) Here, Q is the sensible heat flux (W/m2), αc is the heat transfer coefficient, Ty is the surface temperature (°C), Th is the average air temperature (°C), Ta is the local (at the urban canopy level) and average air temperature difference (°C), and A is the area of the microscopic surface (m2). In their study, Lino and Hoyano made some assumptions for the heat transfer coefficient and the urban canopy and air temperature difference above it (Lino&Hoyano, 1996; Asawa, Hoyano & Nakaohkubo, 2008). Accordingly; • If the wind speed above the urban canopy is 1-2 m/s, turbulent flow occurs under both natural and forced convection conditions. This precludes the calculation of the heat transfer coefficient for any surface. However, suppose the wind speed within the canopy is assumed to be 297 equal to the wind speed above the canopy level. In that case, it is possible to calculate the heat transfer coefficient using the Jurges Formula. • The difference between the air temperature at and above the canopy level is generally 1°C. This difference was ignored in this study, and the temperatures were assumed equal. Consequently, the heat island potential is calculated based on the sensible heat flux, ignoring the heat transfer coefficient and air temperature difference, and is derived as (Lino&Hoyano, 1996). 𝐻𝐼𝑃 = ∑(𝑇𝑠−𝑇𝑎𝑖𝑟)𝑑𝑦 𝐴 (2) Here, HIP is the heat island potential (oC), Ts is the surface temperature (oC), Ta is the air temperature value taken from meteorology (oC), dy is the surface area (m2) and A is the floor area of the urban area whose HIP will be calculated (m2). 2.2. CFD Analysis In this study, Fluent, a CFD software that utilizes the finite volume method, was used. Fluent has been used in many industries worldwide since 1983 and is the most preferred CFD software. Thanks to its advanced solver technology and diverse physical models, it is capable of providing fast and reliable solutions to problems involving conduction, convection, and radiation heat transfer in laminar, transitional, and turbulent flows, problems involving chemical reactions, fuel cells, acoustic flow-induced noise, and multiphase flows (Ansys Fluent,2023). In this study, Fluent was integrated into Ansys Workbench. The Ansys Workbench platform is a system built on the superior knowledge of advanced simulation technology. It enables users to perform all simulation tasks on a single 304 Figure 6. HIP values vary depending on different wall materials Figure 7. Surface temperature values obtained with concrete and asphalt for the Street Figure 8 shows the surface temperature values obtained from simulations using natural stone, which was selected as an alternative material for sidewalks. Compared to concrete pavers, natural stone—having a lower specific heat capacity and a higher thermal conductivity coefficient— caused significant temperature increases, particularly on the south-facing sidewalks. While both material types yielded similar surface temperatures 305 for the north-facing sidewalk, the use of concrete pavers appears to be more appropriate for the south-facing sidewalk in terms of urban heat island potential. Figure 9 presents the HIP values obtained from simulations in which the material type of each urban element was altered. The use of natural stone on façades resulted in the highest increase in HIP, followed by the use of natural stone on sidewalks, which led to the second highest HIP value. The lowest HIP value was obtained from simulations in which concrete was used instead of asphalt for the street, while all other urban elements retained their existing materials. Therefore, it can be stated that materials with high thermal conductivity and high solar absorption coefficients, such as natural stone, have a negative impact on urban heat island potential, regardless of whether they are used for vertical or horizontal urban elements. Figure 8. Surface temperature values obtained with natural stone and concrete paving for pavement 306 Figure 9. Varying HIP values for different surface coating materials Moreover, it is evident that the material chosen for the street—which is the horizontal urban element most exposed to solar radiation in an urban canyon—plays a crucial role in terms of urban heat island potential. Indeed, even replacing only the asphalt material—characterized by a high solar absorption coefficient—resulted in a noticeable reduction in the HIP value. For this reason, when selecting materials for horizontal urban elements that significantly affect urban heat island potential, particular attention should be paid to their thermal conductivity, solar absorption, and emissivity coefficients. 4. Conclusion and Suggestions In this study, which employs computational fluid dynamics, it is possible to create and evaluate different scenario conditions for the examined urban area or any other area by incorporating various parameters. Thanks to the effective use of this method, significant parameters that may influence urban areas have been simulated, allowing for the desired comparisons to be made. Due to both the method employed and the use of the HIP 307 parameter for evaluating results, this study presents a unique application that addresses an issue, potentially providing valuable insights for designers regarding the urban heat island effect in urban design. The use of different materials generally resulted in minor changes in HIP values. The most significant difference was observed when the material used for the street—the horizontal urban element most exposed to solar radiation—was changed. Therefore, when selecting materials for urban areas, greater emphasis should be placed on their thermophysical properties rather than their visual appearance. Materials with lower thermal conductivity, solar absorption, and emissivity coefficients should be prioritized. The conscious selection of urban surface materials not only mitigates the heat island effect but also directly contributes to the health and quality of life by improving the thermal comfort of urban residents. However, further research is needed to gain a more comprehensive understanding of the issue. In the future, comparative analyses using innovative and smart materials for different climate zones will provide practical guidance for urban planners, architects, and policymakers. 308 Acknowledgements and Information Note Ethics Committee approval was not required for the study. Author Contribution and Conflict of Interest Declaration Information All authors contributed equally to the article. There is no conflict of interest. 309 References Ansys Fluent User’s Guide, 2023. Asawa, T., Hoyano, A., & Nakaohkubo, K. (2008). Thermal design tool for outdoor spaces based on heat balance simulation using a 3DCAD system. Building and Environment, 43(12), 2112-2123. Çengel, Y., 2011. Isı ve Kütle Transferi , Güven Bilimsel Yayınevi, İzmir. EPA (2008). http://www.urbanheatislands.com (29.07.2025) Givoni, B., 1998. Climate Consideration in Building and Urban Design, Van Nostrand Reinhold, NY, USA. Google Earth. (www.google.com.tr/intl/tr/earth) 8.02.2023. Göksu, Ç., 1993, Güneş ve Kent. 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Journal of environmental sciences, 20(1), 120-128. 311 Prof. Dr. Ufuk Teoman AKSOY E-mail: [email protected] Educational Status: Prof. Dr., University Member License: Beykent University, Faculty of Engineering and Architecture, Department of Architecture Degree: Fırat University, The Graduate School of Natural and Applied Sciences, Building Education Department. Doctorate: Fırat University, The Graduate School of Natural and Applied Sciences, Building Education Department. Assoc. Prof. Dr. Ayça GÜLTEN E-mail: [email protected] Educational Status: Assoc. Prof. Dr., University Member License: Anadolu University, Faculty of Engineering and Architecture, Department of Architecture Degree:Fırat University, The Graduate School of Natural and Applied Sciences, Building Education Department. Doctorate:Fırat University, The Graduate School of Natural and Applied Sciences, Building Education Department.