Document Type : Research Paper
Authors
1 Associate Professor Of Urban Design in University of Hamadan Bu-Ali Sina University, Faculty of Art and Architecture, Hamadan, Iran
2 Department of Urban Planning, Jundi-shapour University, Dezful, Iran
3 Department of Urban Planning , Bu-Ali Sina University, Hamedan, Iran
Abstract
Climate change and accelerated urbanization have made the redefinition of public space design patterns with a climate-oriented approach inevitable. Despite numerous studies in hot climates emphasizing increased enclosure and shading, a significant knowledge gap exists in explaining optimal massing and spatial enclosure patterns for thermal comfort in cold and semi-arid climates. This research aims to fill this gap by quantitatively investigating the impact of physical indicators—including height-to-width ratio (H/W), shadow angle, and spatial openness—on pedestrians' perception of thermal comfort in Shahid Noubahaar Street, Kermanshah.
The methodological approach of this study integrates three complementary strategies: first, field microclimatic measurements conducted on February 15, 2016, using instruments for temperature, humidity, wind speed, and radiation at 1.5 meters above ground level; second, microclimate simulation using ENVI-met software version 5.5 with 1-meter grid resolution, validated against field data; and third, shadow mask analysis using a protractor tool to calculate shadow angles of eastern and western building fronts at different times of day. Noubahaar Street was selected as the case study due to its enclosure diversity across four distinct sections (A, B, C, D), active land use with high pedestrian traffic, and suitable access for field measurements. Kermanshah, located at 34°19' north latitude and 1,322 meters above sea level, has a cold mountainous climate.
The findings demonstrate that reduced enclosure (lower H/W ratio) during the cold season significantly increases the relationship between mean radiant temperature (Tmrt) and the Predicted Mean Vote (PMV) index. Linear regression analysis confirms a strong correlation (R² = 0.77) between these two variables, meaning that approximately 77% of the variation in pedestrians thermal perception on winter days is explained by received solar radiation. Conversely, high enclosure with stable shadows leads to reduced Tmrt and intensified cold sensation. Shadow angle analysis across the four street sections revealed that the western front (29° angle) and eastern front (23° angle) create significant thermal asymmetry in the existing condition.
Based on these analyses, contextual and quantitative design strategies have been proposed. In Section A, reducing the western front's shadow angle from 29° to 20° through stepped setbacks (second-layer buildings up to 18 meters height followed by 9-meter deep setbacks) along with controlled increase of the eastern front's angle to 30° using strategic evergreen tree planting is recommended. In Section B, permitted height increase in future developments conditional on maintaining 26° shadow angles for both fronts is proposed. Section C, which has the most unbalanced conditions (eastern front 8°, western front 35°), would benefit from reducing the western angle to 32° and increasing the eastern angle to 15°, resulting in significant reduction of shadow coverage at street level by noon and shifting thermal conditions from "cold" to "neutral-comfortable." In Section D, creating spatial openings 7.2 meters deep within building masses, planting deciduous trees with horizontal canopies in the median strip, and installing a horizontal lattice canopy at 4 meters height are proposed.
The discussion reveals that the findings are significantly aligned with existing theoretical and empirical literature while extending and localizing prior knowledge. Unlike hot climates where increased enclosure is the primary strategy, in Kermanshah's cold climate, reduced enclosure and increased spatial openness play a more determining role in winter thermal comfort. This finding fully aligns with Guo et al. (2024) in China's cold climate, confirming the necessity of redefining "optimal enclosure" independently for each climate. Furthermore, the strong correlation between Tmrt and PMV (R² = 0.77) emphasizes the vital role of solar radiation in outdoor thermal comfort, consistent with Ji et al. (2022) and the foundational theories of Höppe (1999) and Matzarakis (1999).
The design strategies demonstrate a multi-seasonal and dynamic approach, not only optimizing winter radiation but also addressing the inherent contradiction of thermal needs across seasons through summer shading. This aligns with Taleghani et al. (2015), who identified semi-open forms as providing the best radiation-shade balance. The creation of spatial openings and small plazas (as proposed for Section D) extends beyond purely climatic solutions to create collective spaces and enhance social life, directly corresponding to Paale and Ginge (2025), who emphasize the link between urban form, thermal comfort, and public space dynamics, considering thermal comfort a necessary condition for civil life and citizen presence in the public realm.
This research, by providing a quantitative and contextual model for intelligent enclosure management in urban streets within cold climates, not only contributes to the development of climate-responsive design knowledge but also provides operational tools for urban designers and planners to enhance environmental quality and public space vitality. The findings conclusively demonstrate that massing and spatial enclosure have direct and significant effects on pedestrians' thermal comfort perception. In cold climates, street design must ensure pedestrian comfort through maximum solar radiation absorption in winter and appropriate shading in summer. The use of deciduous trees, high thermal mass materials, and stepped building setbacks at higher elevations are among the effective strategies in this context.
The research concludes that in north-south oriented streets within cold climates, the height of eastern building fronts affects morning radiation reception, while western front heights influence late-afternoon reception. Through physical modifications and passive solar design strategies—even modest increases in solar radiation—thermal comfort can be meaningfully enhanced. The innovation of this research lies in three levels: methodologically, integrating field measurements, microclimate simulation, and shadow mask analysis; analytically, separately analyzing eastern and western fronts to explain thermal asymmetry; and strategically, extracting quantitative, contextual setback patterns with specific angles (reducing western shadow angle from 29° to 20°, increasing eastern angle from 23° to 30°) that maximize winter radiation while maintaining building density.
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