Evaluation of impact of vegetation on thermal comfort in public spaces (Case study: Jabal Al-Drak residential complex, Shiraz)

Subject Areas : architecture

Mohammadbagher Bigdeli ¹ , Seyedeh Sedigheh Mirgozar Langaroudi ² , Ahmadreza Kaboli ³

1 - Ph.D Candidate, Department of Architecture, Shiraz Branch, Islamic Azad University, Shiraz, Iran
2 - Assistant Professor, Department of Architecture, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.
3 - Assistant Professor, Department of Architecture, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran.

Received: 2024-11-13 Accepted : 2025-03-17 Published : 2025-07-15

Keywords: Thermal comfort, ENVI-met, PMV thermal comfort index, neighborhood green space,

Abstract :

Urban expansion and the need for housing have led to a decrease in green spaces and vegetation, impacting thermal comfort and temperature regulation in cities, resulting in increased air temperatures and heat stress that affect urban life. Given the importance of thermal comfort, extensive research has been conducted in various fields, including plants, building
facades and forms, and urban neighborhoods. Green spaces and vegetation can improve the urban environment and thermal comfort. Vegetation cools the surrounding environment through transpiration and shade, moderating the urban heat island effect and reducing the effects of heat stress on humans. However, the ability of green spaces to mitigate the effects of heat depends on various factors, including the type and form of vegetation and, most importantly, their arrangement in the site. Therefore, proper and intelligent design of vegetation is important for improving thermal comfort and microclimate.
Numerical simulations, such as ENVI-met software, are used to estimate and improve the environmental performance of urban spaces. Studies on thermal comfort in parks and urban open spaces, especially neighborhood parks, are important because these areas are easily affected by small-scale green spaces, and with intelligent design, microclimates can be created for thermal comfort. In this study, the ENVI-met three-dimensional urban microclimate model was used to investigate the thermal environment of an open space in a high-rise residential complex in Shiraz, Iran, on a hot summer day. By examining the site, without vegetation and also to create thermal comfort in a neighborhood park, five different vegetation patterns, including grass, plane trees, cypress trees, and combined trees (plane, cypress) arranged in the direction of the prevailing wind and combined trees (plane, cypress) arranged in the opposite direction of the prevailing wind were investigated. The results showed that increasing vegetation cover leads to improved thermal conditions of the environment, and the broadleaved vegetation pattern with more shading had the best performance compared to other patterns. However, excessive plant density may lead to a decrease in cooling efficiency. Among all the components, the main factor affecting thermal comfort was the mean radiant temperature. Also, for the software validation, field data were collected by a WBGT-2010SD device in the time interval of 10 hours in a street, in four selected points, including air temperature, mean radiant temperature, relative humidity, and air temperature, and similar modeling was done in the software with the existing buildings and also the number and type of vegetation cover. After obtaining the software outputs and examining the correlation between the obtained numbers, with a correlation coefficient of 0.85 to 0.89 in four points of the selected site in the software validation, we reached an acceptable result, which shows the high accuracy of the software. The results of this study showed that proper design of vegetation, including the number, species, and also different patterns of placement in the environment, can help to improve thermal conditions in urban spaces. There is a need for more studies in this field in different seasons.

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