Document Type : Articles extracted from Thesis
Authors
1
Department of Urban Planning & Design, Faculty of Art and Architecture, Shiraz University, Shiraz, Iran
2
Department of Architecture, Faculty of Art and Architecture, Shiraz University, Shiraz, Iran
Abstract
A B S T R A C T
In recent decades, rapid urbanization in conjunction with climate change has intensified urban warming, a phenomenon characterized by elevated air temperatures, reduced wind flow, and the accumulation of heat, which poses significant risks to the health and well-being of residents in densely populated cities. Under these conditions, climatic comfort in urban open spaces, particularly within historic urban fabrics, has emerged as a critical component of sustainable urban design. Historical passageways, as the primary structures of movement and social interaction in traditional cities, are especially vulnerable to climatic stress due to their distinct morphological and physical characteristics. This study aims to develop a typology of historical passageways in the city of Shiraz and to conduct a comparative analysis of their performance from the perspective of outdoor climatic comfort. Initially, relevant indicators affecting outdoor thermal comfort were identified through a review of theoretical literature and authoritative documents. Subsequently, based on field surveys, twelve representative passageways within the historic fabric of Shiraz were selected and classified into four typological categories according to orientation, spatial configuration, and physical attributes. From each category, one representative passageway, namely Sang-e Siah, Haft-Pich, Shahzadeh Mansour, and Emamzadeh Zanjiri, was selected for microclimatic simulation using the ENVI-met software. Five key parameters, including potential air temperature, mean radiant temperature, relative humidity, wind speed, and the Universal Thermal Climate Index, were evaluated at a height of 1.4 meters during summer conditions at 14:00. The findings indicate that the Shahzadeh Mansour passageway provides the most favorable climatic conditions, owing to its semi-enclosed form, appropriate width-to-height ratio, presence of shading elements, and effective air circulation. In contrast, the Sang-e Siah and Emamzadeh Zanjiri passageways exhibit the poorest levels of thermal comfort, primarily due to excessive openness, the absence of shading features, and inadequate ventilation.
Extended Abstract
Introduction
Traditional Iranian cities possessed a coherent and integrated structure in which physical, social, and climatic elements were formed in an organic interrelationship. In this context, the network of passages, as one of the most important elements organizing space, played a fundamental role in connecting different parts of the city, facilitating movement, and shaping social interactions. In these fabrics, connectivity was not merely a functional conceptual relationship, but rather flowed as a fundamental principle in the spatial organization of the city, such that the main passages, by linking the city center to neighborhoods, provided the setting for economic activities, presence, and social vitality. Within such a structure, climatic comfort was regarded as one of the essential prerequisites for the sustainability and livability of urban spaces.
In recent years, the rapid growth of urbanization alongside the impacts of climate change has led to the intensification of the urban heating phenomenon and increased thermal stress in open urban spaces. Rising air temperatures, reduced wind flow, and heat accumulation on built surfaces have threatened the health and comfort of citizens, particularly in high-density cities, and have further emphasized the necessity of climate-based design in public spaces. Although a substantial portion of previous research has focused on thermal comfort in indoor spaces, open urban spaces, especially passages, despite their significant role in quality of life and social interactions, have received less attention.
Thermal comfort in outdoor spaces is influenced by a set of climatic factors such as air temperature, mean radiant temperature, relative humidity, and wind speed, as well as by the physical characteristics of space, and the human thermal response to these conditions is affected by individual and psychological variables. In the historical fabrics of Iran, the alignment of spatial structure with climatic conditions is clearly observable; compact form, narrow passage widths, high enclosing walls, diverse width-to-height ratios, varied orientations, the presence of semi-enclosed elements such as sabats, and the use of vegetation were among the strategies that, by reducing direct solar radiation and increasing shading, provided more favorable thermal conditions in public spaces. Historical passages, as the primary elements of spatial organization and the movement network of traditional cities, play a decisive role in the quality of livability of historical fabrics. However, in many contemporary urban interventions, the climate-responsive capacities of these passages have been overlooked, and the reduction of thermal comfort has challenged their presence, vitality, and liveliness.
A review of the research literature indicates that studies related to climatic comfort in open urban spaces generally fall into three categories, including physical-spatial studies, quantitative research based on climatic indices, and environmental modeling using software such as ENVI-met; nevertheless, studies that address comparative analysis of passages, spatial-climatic typology, and microclimate analysis at the urban network scale remain limited. Accordingly, the present study, through the simultaneous use of typological and spatial morphological analysis, climatic data, and microclimate simulation with ENVI-met software across four types of historical passages in the city of Shiraz, seeks to identify criteria affecting climatic comfort and to present a model for the typology of historical passages, a model that can be applied in the conservation and sustainable regeneration of historical public spaces and the design of contemporary urban passages. Overall, the aim of this research is to identify the physical and climatic factors influencing climatic comfort in historical passages and to classify these passages, and the main research question of this article is which criteria and indicators affect climatic comfort for the purpose of designing historical passages? and also how can the historical passages of the city of Shiraz be classified based on the obtained criteria?
Methodology
The present study was conducted with the aim of typologizing the historical passages of the city of Shiraz and performing a comparative analysis of their climatic performance. This research is applied in nature and has been carried out using a descriptive-analytical approach. In the first step, through library-based studies and a review of the theoretical literature, the indicators and criteria affecting thermal comfort in open urban spaces were extracted and, within the framework of a conceptual model, served as the basis for analysis. In the next step, by conducting field studies in the historical fabric of the city of Shiraz, 12 valuable historical passages were identified and classified into four main types based on geographical orientation, spatial form, and physical characteristics. This typology was developed with the aim of facilitating the comparative examination of climatic comfort conditions in historical passages, with an emphasis on the role of orientation in wind flow patterns. Subsequently, one passage from each type was selected as a representative case, including the Sang-e Siah, Haft-Pich, Shazdeh Mansour, and Emamzadeh Zanjiri passages. To evaluate the climatic conditions of these passages, numerical simulations were carried out using ENVI-met software. The simulations were conducted in the summer season, at 14:00 as one of the hottest hours of the day, and at a height of 1.4 meters above ground level, corresponding to the level of human activity. In this process, five key indicators, including potential air temperature, mean radiant temperature, relative humidity, wind speed, and the Universal Thermal Climate Index (UTCI), were evaluated to enable a more comprehensive analysis of the climatic comfort conditions of the passages. Additionally, in each simulation, a number of receptors were used for point-based and more precise examination of the mean radiant temperature indicator with the aid of charts in Excel software.
Result and Discussion
The present study is devoted to the examination and comparative analysis of the historical passages of Shiraz from the perspective of climatic comfort. Although historical passages were formed as part of an interconnected network, they exhibit considerable diversity in terms of orientation, spatial form, materials, and shading elements. Accordingly, 12 valuable historical passages were identified and classified into four main types: Type I (A) includes the Sang-e Siah, Seyyed Zolfaghar, and Nasir Nezam passages with a northeast–southwest orientation; Type II (B) includes the Emamzadeh Zanjiri, Abi Zareh, Haj Zeynal, and Sarbagh passages with an east–west orientation; Type III (C) includes the Shazdeh Mansour, Mansouriyeh, and Haj Asghar Bazaarcheh passages with a northwest–southeast orientation; and Type IV (D) includes the Haft-Pich and Filliha Bazaarcheh passages with a northeast–southwest orientation. For each type, based on physical characteristics and their effects on wind flow and shading, one representative passage (Sang-e Siah Passage, Emamzadeh Zanjiri Passage, Shazdeh Mansour Passage, and Haft-Pich Passage) was selected for simulation in ENVI-met software.
Subsequently, the analysis of five climatic indicators, including potential air temperature, mean radiant temperature (MRT), relative humidity (RH), wind speed, and the UTCI index, shows that physical and morphological differences have a direct and significant impact on thermal comfort. Sang-e Siah Passage, with stone paving, brick walls, and the absence of canopies or sabats alongside vegetation in some locations, experiences the highest potential air temperature (maximum 52.62°C) and a mean radiant temperature exceeding 72°C. Wind speed in this passage is very low, and relatively high relative humidity has also failed to improve thermal comfort conditions; the UTCI index likewise indicates severe thermal stress and unfavorable conditions for human presence. In contrast, Shazdeh Mansour Passage, with a semi-enclosed form, sabats and canopies, an appropriate width-to-height ratio, and asphalt paving, has the lowest potential temperature (50.18°C) and a controlled mean radiant temperature (between 62.75 and 65.45°C). Uniform and appropriate wind flow along the passage has reduced thermal stress, and the UTCI index has also recorded the lowest value.
This passage offers the best climatic conditions, and human presence within it is more comfortable. Haft-Pich Passage, with a winding form and an initial sabat, demonstrates moderate performance. Potential temperature and mean radiant temperature are reduced compared to Sang-e Siah, but wind flow is limited in some sections and the distribution of relative humidity is also uneven. The UTCI index indicates that despite reduced direct radiation, conditions still fall within the range of relatively severe thermal stress. Emamzadeh Zanjiri Passage, with an east–west orientation and the absence of vegetation and shading elements, exhibits moderate to weak conditions; high potential temperature, a mean radiant temperature of around 70°C, and the distribution of radiation along the passage axis indicate a high UTCI index and low thermal comfort levels. Furthermore, more detailed analysis using receptors clarifies the role of physical characteristics more explicitly. In Sang-e Siah Passage, comparison of different receptors shows that ground surface material (asphalt or stone paving) has a minor effect on mean radiant temperature, while vegetation cover and the height-to-width ratio of the passage create significant differences. For example, the presence of vegetation at one receptor resulted in a reduction of more than 6 degrees in radiant temperature compared to a receptor without vegetation, and an increase in the height-to-width ratio reduced temperature by about 4 degrees. This indicates that shading and enclosure of passages are vital for heat control. In Haft-Pich Passage as well, the receptors showed that greater wall height and narrower passage width reduce radiant temperature by up to 17 degrees. In addition, the presence of sabats and shading reduced radiant temperature to about 43°C during the hottest hours of the day and played an important role in reducing thermal stress. The winding form of the passage, with its angles and bends, has caused heat accumulation and reduced natural ventilation in some areas. These comparisons indicate that physical elements, including shading devices, height-to-width ratio, path geometry, vegetation cover, and ground materials, are effective in determining thermal comfort.
Conclusion
The results of this study indicate that the thermal behavior of the historical passages of the city of Shiraz has a direct and significant relationship with the physical and morphological characteristics and climatic elements present in each passage. An examination of representative passages such as Shazdeh Mansour, Haft-Pich, Sang-e Siah, and Emamzadeh Zanjiri shows that spatial form, height-to-width ratio (H/W), passage orientation, and the presence of shading elements play a highly effective role in improving thermal comfort conditions. ENVI-met software simulations indicate that Shazdeh Mansour Passage, with an appropriate height-to-width ratio, the presence of sabats and effective shading devices, and the possibility of wind penetration, provides the best thermal comfort conditions.
Mean radiant temperature, potential temperature, and the UTCI index in this passage are noticeably lower than in the other passages, and the uniform wind flow enhances the effect of shading and reduces thermal stress. Similarly, Haft-Pich Passage, with its organic and winding form, has been able to reduce direct solar radiation and control perceived temperature, although limited ventilation and uneven distribution of relative humidity have resulted in moderate thermal comfort conditions. Receptor analysis showed that increasing wall height and narrowing the passage can reduce radiant temperature by up to 17 degrees, and the presence of sabats reduced radiant temperature to about 43°C during the hottest hours of the day and played an important role in reducing thermal stress.
In contrast, Sang-e Siah and Emamzadeh Zanjiri passages, due to excessive openness, lack of effective shading elements, inappropriate orientation, and unfavorable ventilation, experience the highest potential temperature and mean radiant temperature, and the UTCI index indicates unfavorable conditions and high thermal stress for human presence. Even the presence of relatively high relative humidity has not been able to compensate for the negative effects of the lack of shade and inadequate wind flow.
Overall, comparison of receptors and output maps shows that physical elements, including height-to-width ratio, passage orientation, sky view factor (SVF), the presence of sabats and shading devices, vegetation cover, and materials with appropriate reflectance, are more influential than any other factors in enhancing thermal comfort. Ultimately, the present study emphasizes that climate-based design and the use of strategies such as the creation of semi-enclosed spaces, appropriate shading, controlled height-to-width ratios, and favorable wind flow are key to enhancing thermal comfort in historical passages. Shazdeh Mansour Passage represents a prominent example of successful performance, Haft-Pich Passage exhibits relatively improved conditions, and Sang-e Siah and Emamzadeh Zanjiri passages require reconsideration and improvement of climatic strategies.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
Conflict of Interest
Authors declared no conflict of interest.
Acknowledgments
The authors would like to thank the editor and anonymous reviewers for their valuable comments and constructive remarks.
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