An Evaluation of Thermal Performance of Urban Fabrics in Tehran Climate: Implications for Micro Climate-Sensitive Urban Design

Document Type : Research Paper

Authors

1 Professor, School of Urban Plannig, College of Fine Arts, University of Tehran, Tehran, Iran.

2 Professor, School of Urban planning, College of Fine arts, University of Tehran

3 PhD Student, School of Urban Planning, College of Fine arts, University of Tehran

Abstract

Over-urbanization negatively affects on urban temperatures and results in the formation of urban heat islands. Outdoor thermal comfort (OTC) occurs in such exacerbated conditions, influencing health, well-being, and productivity of urban dwellers. Therefore, cities need to urgently evaluate the OTC and act to ensure providing acceptable OTC in built-up settings. As such, many studies envisaged to understand outdoor thermal performance of urban environments based on their geometrical features and suggest mitigation strategies against the negative effects of heat stress. Reviewing the literature reveals that most of the previous studies are focused on the urban scenarios of a single canyon or a limited number of individual buildings with simplified and uniform geometrical features without including the effect of surrounding urban neighborhoods. Furthermore, most studies only calculate OTC at a certain time and location in the space where field measurements are conducted. Since these field measurements are scattered in time and space, the comprehensive tempo-spatial distributions of OTC cannot be achieved to have a comprehensive understanding of outdoor environments performance. In this regards, the OTC tempo-spatial visualization is essential in outdoor environments. This study aims to develop a framework to comprehensively evaluate the performance of OTC and assess the effect of geometrical features on the spatial and temporal distribution of thermal comfort in residential neighbourhoods. The proposed framework is applied to the case study of Tehran city where three residential urban configurations are selected with different geometrical features (organic, orthogonal and apartments block) to conduct a series of high-resolution simulations. This study follows a step by step process to understand the impact of built-up urban areas on their thermal comfort performance: (1) development of 3-D models of three selected neighborhoods, (2) tempo-spatial OTC analysis, (3), and understanding the impact of geometrical parameters on the thermal comfort performance. The study reveals that all the selected areas have a significant deviation from the acceptable comfort range with mostly moderate and strong heat stress. The differences in OTC performance of these areas is related to the geometrical features of buildings and canyons including neighborhood layout and proportion of open and built-up areas and canyons’ profiles (building’ height, aspect ratio and orientation). The spatial variation of OTC is more significant in orthogonal areas and apartment complexes while organic settings provide a less distributive comfort performance with lower hours of heat stress and discomfort. Results show that the cooling effect of organic neighborhoods is higher due to the higher rate of aspect ratio in canyons. Orthogonal and apartment cases have higher mean radiant temperature mostly above 40°C. In the apartment complex, open spaces show the highest rate of heat stress, due to the long exposure to shortwave solar radiation. In this area, the most important domain of retrofitting strategies should be focused on landscape planning for green planting and water bodies. The results of this study help to identify design solutions that should be incorporated in the planning studies and as a result, a holistic perspective would be achieved for better decision-making via this tempo-spatial comprehensive analysis.

Keywords

References

توسلی، محمود (1381)، ساخت شهر و معماری در اقلیم گرم و خشک ایران، پیوند نو، تهران.
حیدری، شاهین (1393)، سازگاری حرارتی در معماری نخستین قدم در صرفه جویی مصرف انرژی، موسسه چاپ و انتشارات دانشگاه تهران، تهران.
حیدری، شاهین، منعام، علیرضا (1392)، ارزیابی شاخصه‌های‌ آسایش حرارتی در فضای باز، جغرافیا و توسعه ناحیه ای، سال یازدهم، شماره 20، صص 216-197.
طاهباز، منصوره (1386)، طراحی سایه در فضای باز، هنرهای زیبا-معماری و شهرسازی ، دوره 31، شماره 31، صص- 27-38.
مجیدی، فاطمه، حیدری، شاهین (1397)، تفاوت فصلی حدود آسایش حرارتی در محلات قدیم و جدید شهر اصفهان (مطالعه موردی: محلات جلفا و مرداویج)، هنرهای زیبا-معماری و شهرسازی، دوره 23، شماره 2، صص 42-31.
 
Ahmed-Ouameur, F. and Potvin, A. (2007), Microclimates and thermal comfort in outdoor pedestrian spaces a dynamic approach assessing thermal transients and adaptability of the users, in Proceedings of the solar conference, p. 592.
Ali-Toudert, F. and Mayer, H. (2006), Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate, Building and environment, Elsevier, 41(2), pp. 94–108.
Alznafer, B. M. S. (2014), The impact of neighbourhood geometries on outdoor thermal comfort and energy consumption from urban dwellings: a case study of the Riyadh city, the kingdom of Saudi Arabia, p. 344.
Blazejczyk, K., Epstein, Y., Jendritzky, G. and Tinz, B. (2012), Comparison of UTCI to selected thermal indices, International journal of biometeorology, Springer, 56(3), pp. 515–535.
Chen, L., Yu, B., yang, F. and Helmut, M. (2016), Intra-urban differences of mean radiant temperature in different urban settings in Shanghai and implications for heat stress under heat waves: a GIS-based approach, Energy and Buildings, Elsevier, 130, pp. 829–842.
Cheung, P. K. and Jim, C. Y. (2018), Subjective outdoor thermal comfort and urban green space usage in humid-subtropical Hong Kong, Energy and Buildings, 173, pp. 150–162.
Deng, J.-Y., and Wong, N. H. (2020). Impact of urban canyon geometries on outdoor thermal comfort in central business districts. Sustainable Cities and Society, 53, 101966.
Fiala, D., Havenuth, G., Brode, P., Kampmann, B. and Jendritzky, G. (2012), UTCI-Fiala multi-node model of human heat transfer and temperature regulation, International journal of biometeorology, Springer, 56(3), pp. 429–441.
Galindo, T. and Hermida, M. A. (2018), Effects of thermophysiological and non-thermal factors on outdoor thermal perceptions: The Tomebamba Riverbanks case, Building and Environment, 138, pp. 235–249.
Gharai, F., Masnavi, M. and Hajibandeh, M. (2018), Urban Local-Spatial Resilience: Developing the Key Indicators and Measures, a Brief Review of Literature, Bagh-e Nazar, 14(57), pp. 19–32.
Hsieh, H.-F. and Shannon, S. E. (2005) ‘Three approaches to qualitative content analysis’, Qualitative health research. Sage publications Sage CA: Thousand Oaks, CA, 15(9), pp. 1277–1288.
ISO Standard (1998), ISO 7726: Ergonomics of the thermal environment—Instruments for measuring physical quantities, International Organization for Standardization.
Jamei, E. and Rajagopalan, P. (2017), Urban development and pedestrian thermal comfort in Melbourne, Solar Energy, Elsevier, 144, pp. 681–698.
Kim, J., Schiavon, S. and Brager, G. (2018), Personal comfort models – A new paradigm in thermal comfort for occupant-centric environmental control, Building and Environment, Elsevier, 132, pp. 114–124.
Li, K., Zhang, Y. and Lihua, Z. (2016), Outdoor thermal comfort and activities in the urban residential community in a humid subtropical area of China, Energy & Buildings, Elsevier, 133, pp. 498–511.
Lindberg, F. et al. (2016), The impact of urban planning strategies on heat stress in a climate-change perspective, Sustainable Cities and Society, Elsevier, 25, pp. 1–12.
Nazarian, N., Sin, T. and Norford, L. (2018), Numerical modeling of outdoor thermal comfort in 3D, Urban climate, Elsevier, 26, pp. 212–230.
Oke, T. R. (2002), Boundary layer climates, Routledge, London.
Perini, K. and Magliocco, A. (2014), Effects of vegetation, urban density, building height, and atmospheric conditions on local temperatures and thermal comfort’, Urban Forestry & Urban Greening, Elsevier, 13(3), pp. 495–506.
Taleb, H. (2014), Enhancing the thermal comfort on urban level in a desert area: Case study of Dubai, United Arab Emirates, Urban forestry & urban greening, Elsevier, 13(2), pp. 253–260.
Taleghani, M., Kleerekoper, L., Tenpierik, M. and Dobbelsteen, A. (2015), Outdoor thermal comfort within five different urban forms in the Netherlands, Building and Environment, 83, pp. 65-78.
Thorsson, S., Lindberg, F., Ingegard, E. and Holmer, B. (2007), Different methods for estimating the mean radiant temperature in an outdoor urban setting, International Journal of Climatology: A Journal of the Royal Meteorological Society, Wiley Online Library, 27(14), pp. 1983–1993.
https://www.google.com/earth/
 
 
Journal of Fine Arts: Architecture & Urban Planning
Volume 25, Issue 1
March 2020
Pages 5-15

Files

Share

How to cite

Statistics