Document Type : Research Paper
Authors
Department of Urban Planning and Design, Faculty of Art & Architecture, University of Shiraz, Shiraz, Iran.
Abstract
Highlights
- The historical design of the Sang-e Siah neighborhood passively harmonized with climatic conditions, ensuring high spatial quality and thermal comfort.
- Physical modifications in Shiraz's historical urban fabric have weakened the ability of urban geometry to regulate microclimatic conditions effectively.
- Neglecting the microclimatic effects of urban geometry leads to a decline in both thermal comfort and environmental quality in urban open spaces.
- The principles embedded in Shiraz's historical urban design provide valuable insights for sustainable and climate-responsive urban development.
Introduction
The rapid pace of urbanization and its associated environmental challenges, coupled with the rising demand for energy to regulate thermal conditions, have underscored the necessity of addressing the microclimatic consequences of urban development. Given the increasing global temperatures and the urgency of climate adaptation, it is essential to examine the impact of urban form on microclimatic conditions and thermal comfort.
The historical urban fabric of Shiraz, particularly in the Sang-e Siah neighborhood, represents an exemplary case of passive adaptation to climatic conditions. Through careful spatial planning, traditional urban layouts optimized thermal comfort by minimizing solar exposure and enhancing ventilation. However, recent modifications to the city's historical districts have undermined these adaptive strategies, leading to increased urban heat stress and a reduction in outdoor comfort levels.
Meteorological records from Shiraz indicate a persistent rise in average temperatures, aligning with global climate change trends. These data highlight the importance of incorporating climate-sensitive urban design strategies to improve thermal comfort. The traditional design of Shiraz’s historic districts, characterized by narrow alleys, shaded pathways, and strategically oriented streets, exemplifies an effective response to the city's climatic challenges. This study aims to quantitatively assess the impact of geometric transformations in the Sang-e Siah neighborhood on microclimatic conditions and thermal comfort.
Theoretical Framework
Urban geometry consists of key parameters such as the sky view factor (SVF), height-to-width (H/W) ratio, and street orientation, all of which play a critical role in influencing climatic factors such as solar radiation exposure, wind flow, temperature distribution, and humidity retention. These elements collectively determine the thermal comfort of outdoor urban spaces.
A reciprocal relationship exists between urban microclimates and broader climatic systems, with urban geometry serving as a crucial intermediary. By adopting climate-responsive urban design principles, planners and designers can mitigate unfavorable microclimatic effects, ensuring more livable and thermally comfortable urban environments. This study examines the extent to which changes in urban form influence these parameters and provides recommendations for sustainable urban planning practices.
Methodology
This research employs a descriptive-analytical approach and falls within the category of applied studies. Data collection was carried out through a combination of historical document analysis, field surveys, and meteorological data evaluation. The ENVI-met software, a highly reliable microclimate simulation tool, was utilized to model the impact of physical alterations on thermal comfort in the Sang-e Siah neighborhood.
To ensure the accuracy of the findings, simulated results were compared against on-site temperature, humidity, and wind speed measurements. The study focused on the hottest day of the year—July 1, 2022—to capture extreme temperature conditions and their effects on urban microclimates. This methodological approach provides a robust basis for assessing the thermal performance of the historical urban geometry and its contemporary modifications.
Discussion and Findings
The findings of this study underscore the significant impact of geometric transformations in the neighborhood on microclimatic conditions. Specifically, the increase in SVF and the reduction in H/W ratios have resulted in the following effects:
Elevated ambient temperatures due to increased exposure to solar radiation.
Enhanced radiant heat effects, leading to a measurable decline in thermal comfort.
Increased wind speeds in specific areas, contributing to dust dispersion while simultaneously reducing humidity levels.
Decreased humidity, which intensifies heat stress and exacerbates outdoor discomfort.
These combined effects have significantly reduced outdoor thermal comfort in the study area. The results emphasize the importance of maintaining traditional urban design principles to ensure microclimatic stability in historic districts.
Conclusion
This study confirms that urban geometry variables such as SVF, H/W ratio, and street orientation play a fundamental role in shaping microclimatic conditions. The historical structures in Shiraz were designed in harmony with local climatic conditions, employing passive cooling strategies that enhanced thermal comfort in outdoor spaces. However, modern transformations—particularly the widening of streets and reductions in building heights—have disrupted this balance, exacerbating urban heat stress.
To promote sustainable urban development, urban planners and designers should integrate lessons from Shiraz’s historical urban fabric. Strategies such as limiting SVF through shaded pathways, maintaining optimal H/W ratios for improved thermal regulation, and orienting streets to maximize natural ventilation can serve as effective guidelines for improving urban thermal comfort in Shiraz and other arid cities experiencing similar climatic challenges.
Keywords
- Thermal comfort
- climate-responsive design
- urban geometry
- urban microclimate
- Sang-e Siah Historical Quarter
- Shiraz
Main Subjects
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