Extended Abstract

Introduction

Traditional Iranian cities have historically been shaped upon principles of morphological harmony, social cohesion, and climatic adaptability. Among the fundamental components of this urban fabric, passageways (gozar) played a multidimensional role, functioning not only as routes of mobility but also as spaces for social interaction, cultural exchange, and economic activities. With their spatial-climatic configuration, these passageways substantially contributed to the thermal comfort of residents. In contemporary times, however, morphological transformations induced by urban expansion, the reduction of vegetative cover, and the intensification of impervious surfaces have triggered severe thermal stresses in urban environments, underscoring the necessity of re-examining historical spatial models. While numerous studies have addressed outdoor thermal comfort, most have focused either on limited thermal indices or on single-dimensional elements, leaving comparative typological studies of historical passageways in relation to microclimate largely unexplored. The present research seeks to analyze and classify the typologies of Shiraz’s historical passageways through the theoretical framework of climatic comfort and microclimatic simulation, and to propose strategies for improving their environmental performance.



Methodology

The methodology integrates literature review, field analysis, and simulation modeling using ENVI-met. First, the theoretical foundations of outdoor thermal comfort and key indicators—including Mean Radiant Temperature (MRT), Potential Air Temperature (Ta), Relative Humidity (RH), Wind Velocity, and the Universal Thermal Climate Index (UTCI)—were reviewed, leading to the development of the conceptual framework. The historical fabric of Shiraz within District 8, encompassing 360 hectares with multiple historically significant passageways, was selected as the study area. Within this scope, twelve passageways with diverse morphological and orientational characteristics were identified and classified into four principal typologies. From each typology, one representative passageway (Sang-e Siah, Emamzadeh Zanjiri, Shahzadeh Mansur, and Haft-Pitch) was chosen for microclimatic simulation under extreme summer conditions (1 July, 14:00). Meteorological data were extracted from the 50-year EnergyPlus database, while standardized human and climatic parameters were defined for UTCI calculation. Simulation outputs were generated as climatic maps and numerical datasets, further analyzed through Leonardo and Microsoft Excel. Additionally, several receptors with varying morphological parameters (height-to-width ratio, presence or absence of sabats, pavement materials, and vegetative cover) were embedded in each passageway to allow precise evaluation of individual factors.



Results and discussion

Findings revealed that morphological and spatial variations across passageways exerted significant and direct impacts on microclimatic indices. Regarding Potential Air Temperature, Sang-e Siah—with its high openness and lack of shading—registered the highest temperatures and lowest comfort levels, whereas Shahzadeh Mansur, benefiting from favorable height-to-width ratios and the presence of sabats, demonstrated cooler and more balanced conditions. Mean Radiant Temperature emerged as the most decisive factor: in Sang-e Siah, MRT peaked at 73°C, indicating severe inefficiency in solar radiation control, while Haft-Pitch—with its twisted geometry and narrow profile—recorded markedly lower values. Relative Humidity analysis indicated that, despite its thermal shortcomings, Sang-e Siah benefited from vegetative cover and openness, performing better than other passageways, though still unable to achieve comfort thresholds. Conversely, Emamzadeh Zanjiri exhibited the poorest RH values. In terms of wind velocity, Emamzadeh Zanjiri, owing to its alignment with prevailing winds, achieved relatively effective ventilation, while Sang-e Siah and Haft-Pitch experienced poor airflow due to blockages. The integrated UTCI analysis—representing human thermal perception—demonstrated that Shahzadeh Mansur offered the most favorable comfort conditions, Haft-Pitch performed moderately, and both Emamzadeh Zanjiri and Sang-e Siah fell within the category of severe heat stress.

Comparisons across receptors further underscored the critical influence of morphological parameters. Results showed that increasing the height-to-width ratio (H/W) could lower MRT by several degrees, with taller and narrower passageways yielding more favorable climatic conditions. Vegetative cover, in certain segments, reduced MRT by over 6°C, while the presence of sabats—a vernacular architectural element—proved highly effective in moderating peak summer heat and sustaining pedestrian usability. Pavement material, although less impactful, revealed asphalt to slightly intensify ambient heat due to higher solar absorption.

Conclusion

Overall, the study emphasizes the decisive role of morphological configuration and spatial design in enhancing outdoor climatic comfort. Shahzadeh Mansur, characterized by effective climatic modifiers such as sabats, shading devices, and optimal height-to-width proportions, performed most successfully, while Sang-e Siah, with excessive openness and absence of climatic mediators, experienced the most critical conditions. Haft-Pitch offered moderate success in controlling radiation and air temperature yet was deficient in ventilation and humidity regulation. Emamzadeh Zanjiri, despite acceptable airflow, provided overall the least favorable comfort levels. These findings highlight that the revitalization of historical passageways and the design of contemporary urban corridors must prioritize proportional street canyons, effective shading structures, integration of vegetation, climatically responsive materials, and facilitation of wind flow.