Urban Ecology
Hassan sajadzadeh; Mohsen Taban; Maryam Jafari
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 ...
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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.
Urban Design
Farzaneh Amoozadeh; Sara Soleimani
Abstract
HighlightsUrban designs that allow the incorporation of natural elements lead to improved environmental quality.Deepening urban valleys facilitates greater wind flow from lake surfaces, enhancing cooling effects.Reducing building surface coverage enhances airflow and improves thermal comfort.Increasing ...
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HighlightsUrban designs that allow the incorporation of natural elements lead to improved environmental quality.Deepening urban valleys facilitates greater wind flow from lake surfaces, enhancing cooling effects.Reducing building surface coverage enhances airflow and improves thermal comfort.Increasing building height and decreasing the surface coverage factor (SC) reduces temperature levels. IntroductionUrban areas are responsible for two-thirds of the world’s primary energy consumption, which contributes significantly to urban heat islands (UHI) (Keirstead et al., 2012). UHIs are a major environmental issue, characterized by higher urban temperatures due to concentrated human activities. This study examines the cooling effects of Chitgar Lake on its surrounding urban area, aiming to mitigate future heating issues in Tehran by exploring how urban lakes can influence UHI. Specifically, it analyzes the role of urban geometric configurations in mitigating heat around lakes, which serve as urban open spaces.Theoretical FrameworkUrban planners utilize indicators like Floor Area Ratio (FAR), Surface Coverage (SC), and Building Height (H) to regulate urban forms. FAR relates to building volume, while SC denotes the proportion of built surfaces, indicating building permeability. Figure 1 illustrates the calculation of FAR and SC.Figure 1: Illustration of Urban Planning Indicators - FAR and SC.Among urban morphology elements, water bodies (e.g., rivers and lakes) significantly impact urban heat islands (Sarralde et al., 2015). The cooling effect of urban water bodies results from two main mechanisms: (a) evaporation, and (b) latent heat absorption, both of which lower surrounding temperatures compared to areas without water.MethodologyThis research compares two time periods—before and after the construction of Chitgar Lake—to assess the lake’s cooling effects on its surroundings. Two critical thermal conditions were selected from each period: one representing the environment after the lake’s construction and another before it. Meteorological data from these periods were analyzed, and simulations were conducted using the ENVI-met modeling software. The Physiological Equivalent Temperature (PET) was subsequently calculated with Biomet software (Wang et al., 2021).Figure 2: Research Process Diagram (a) and Sample Model Descriptions (b).Results and DiscussionComparison of Conditions Pre- and Post-Lake Construction: Simulation data reveal a general temperature decrease in the area following Chitgar Lake’s construction. Model A, representing the current urban fabric, acts as a heat absorber. Although it generates a warmer atmosphere, the shadowed areas remain cooler, providing enhanced thermal comfort. In Model A, humidity intensifies during pre-dawn hours, gradually decreasing as sunlight increases.Impact of Height-to-Width Ratio: Taller buildings deepen urban valleys (H/W > 1), casting longer shadows that lower temperatures and improve thermal comfort. However, these deep valleys tend to retain moisture due to limited sunlight and airflow. In contrast, shorter valleys (H/W < 1) permit more sunlight and airflow, leading to reduced humidity but higher temperatures, resulting in less favorable thermal comfort.Comparison of Urban Form Layout: Analyzing the SB-1 and SB-2 models showed that increasing building height and reducing surface coverage (SC) lead to temperature reductions due to higher FAR (increased density). Larger cross-sectional areas hinder wind flow, retaining humidity in street valleys. The urban form model with the best thermal comfort index was CC-2, characterized by high humidity and optimal thermal conditions. Conversely, SB-1, with a high occupancy coefficient and high permeability, exhibited the most critical thermal state, acting as a heat absorber with elevated temperatures.ConclusionThis study demonstrates that urban open spaces with natural cooling elements, such as water bodies, along with wind flow and shading, significantly improve thermal comfort during hot summer days. Models show that urban spaces allowing natural factors to penetrate are of higher quality. As building height increases and urban valleys deepen, extended shadows help lower temperatures and create areas with balanced thermal comfort. Streets oriented from northeast to southwest, and to a lesser degree east-west, experience the lowest temperatures while maintaining high humidity, which improves thermal comfort through lake-enhanced wind flow.Additionally, denser urban street valleys with low permeability hinder wind flow, contributing to inadequate thermal comfort. This study found that modifying urban form, building orientation, and the height-to-width ratio can enhance urban valley permeability, reducing thermal pollution effects and lowering cooling energy demands.
Urban Ecology
mahsa samadpour shahrak; Mehrdad Karimimoshaver
Abstract
Highlights- The research considered the effect of planting patterns on thermal comfort.- The research addressed population increase and its effect on the morphology of cities.- The results of comparison between the scenario without trees and the others demonstrate that the thermal comfort conditions ...
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Highlights- The research considered the effect of planting patterns on thermal comfort.- The research addressed population increase and its effect on the morphology of cities.- The results of comparison between the scenario without trees and the others demonstrate that the thermal comfort conditions exhibit great changes, and all the scenarios create better environmental conditions than the scenario without trees.- The findings show that simply moving vegetation and trees without changing their nature and dimensions and the environment can improve comfort to some extent. IntroductionThe increasing population has changed the morphology of cities and caused changes in the surrounding environmental conditions. Green space per capita is about 4.5 square meters in Iran, which is quite different from the global standard: 20 to 25 square meters per person (Haashemi et al., 2016). As a result, it seems necessary to increase the amount of greenery in cities. Lee et al. (2016) introduce shading and ventilation as the main factors in the improvement of thermal comfort conditions in the environment using trees. Vegetation reduces mean radiant temperature and improves environmental conditions through evaporation and daylight control and reflection (Salata et al., 2017). It plays a major role in the regulation of weather conditions by controlling and conducting wind flow and reducing wind speed and pressure (Perini et al., 2018).Theoretical FrameworkThermal comfort involves conditions of perception in which the surrounding environment is thermally satisfactory (Ashrae, 1997). In their review of the studies conducted in the field of thermal comfort in outdoor spaces, Johnson et al. have introduced the predicted survey average index as one of the most widely used indices among ones such as SET and UTCI. (Johansson et al., 2013). This index has been widely used in different regions with different climates (El-Bardisy et al., 2016; Salata et al., 2015; Abdi et al., 2020).This model was designed by Fanger in 1970, considering factors such as air temperature, average radiant temperature, and relative humidity and two personal variables including clothing resistance and activity level, used as a composite index. This index specifies the coefficients that are measured according to Asher’s thermal scale and indicates the average thermal sensation of a large group of people in a certain space (Fanger, 1970). Therefore, considering and measuring this index causes other microclimatic factors to be taken into account and obtained through the following formulae:PMV=(0.303e-0.036m+0.028)[(M-W)-H-Ec-crec-Erec]E=3.05×10-3(256tsk-3373-pa)+EswEc=3.05×10-3[6.99×5733(M-W)-pa]+0.42(M-W-58.15)Crec=0.0014M(34-Ta)Erec=1.72×10-5M(5867-Pa).The value of H can be measured directly and calculated using the following equation:H=Kcl=tsk-tcl/Icl.Moreover, previous research has pointed out the importance of planting patterns, trees, and vegetation and their impact on the environmental and microclimatic conditions of the region. The question that arises now is what kind of tree planting pattern, among the common ones, can have a better impact on the environment. In this study, therefore, the four common planting patterns of sextuple, quadruple, row, and scattered were selected to be applied in the same conditions and with the same number of trees.MethodologyIn this research, the ENVI-met software was used because the output provides most of the parameters required for thermal comfort, such as Ta, Tmrt, and wind speed (Taleghani et al., 2015), and the results have been validated and used by researchers (Taleghani et al., 2018). For data measurement, five receptors were selected at the central points of the site. These receptors were located so as to be scattered in the site and be capable of expressing the general state thereof. Therefore, three receptors at the central points of the site and two located around the site were selected. Moreover, because the average human height between the positions of sitting and standing is 1.50 meters, the simulation measurement was carried out at this height. The environmental data and information on the receptors were extracted during the study hours (10 am to 9 pm), and the average value was calculated for the predicted survey average index.Results and DiscussionThe analysis of the data and figures extracted from the software demonstrates that a more uniform shade is created in the environment in the scattered pattern than in the others, and because the trees are scattered in most parts of the site, solar access is more limited there than in the other scenarios. Moreover, ventilation conditions are easier in the row pattern than in the scattered pattern, and the warm wind passes through the trees more easily there due to the regular arrangement. Therefore, the best planting pattern is the one that creates the more uniform shade and better ventilation conditions. However, the results of the scattered pattern are the same in most parts of the site, and there is only a little difference between them in some cases. As a result, the scattered and row patterns of tree planting are better than mass planting and concentrated in certain parts of the site.ConclusionThe results of comparing the treeless scenario to the others demonstrate that the thermal comfort conditions change to a large extent, and all scenarios create better environmental conditions than the treeless state. Moreover, because the row pattern exhibits a lower average PMV for most receptors and most hours of the day, it is the best pattern. The sextuple pattern has high indices in most cases, and the quadruple pattern has a similar function to the sextuple one. Therefore, it can be concluded that the row and scattered patterns create better comfort conditions than the others. The results of this research can be used by architects, landscape designers, and urban designers. In this research, different patterns of trees have been compared, so future research can involve comparison of other plantings such as grass and shrubs and of the effects of different planting patterns.
Urban Sustainability
seyed majid mofidi shemirani; seyedeh maryam hoseini; haniyeh sanayeiyan; gholamreza japalaghi
Abstract
Throughout the past century, cities have lost their vital connection with the nature due to the fundamental changes in their functions and physical forms. The development of urbanization and attachment of villages to metropolises in recent years have led to destruction of vegetation in these regions. ...
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Throughout the past century, cities have lost their vital connection with the nature due to the fundamental changes in their functions and physical forms. The development of urbanization and attachment of villages to metropolises in recent years have led to destruction of vegetation in these regions. The importance of identifying the effects of cities on their climates can be indicated only through accurate research and quantitative assessment. The overall increase in air temperature as a result of urbanization is 1-3 degrees Celsius. In stable climatic conditions, however, the air temperature difference between urban and suburban areas can be as high as 10 degrees Celsius. Increasing the amount of vegetation, planting trees, and developing ecological networks are some of the effective passive methods available for improvement of microclimates. Similar methods have been used in the ancient cities of Iran, where the temperature inside the cities has always been lower than that of the surrounding areas due to the utilization of a special type of urban planning which has been capable of providing appropriate climatic conditions at micro scale by controlling climatic elements. Ozgol is one of the northern neighborhoods of Tehran, where green spaces have diminished as a result of the development process and space quality at the centralized focal points has decreased. This study attempted to identify the relationship between green areas and temperature decrease on the hottest day of the year to help improve the quality of the public spaces and increase thermal comfort at the focal points of the neighborhood. This research used a hybrid methodology based on logical reasoning and software-assisted assessment to study a site in the Ozgol neighborhood under two conditions: current status and optimal design. The data on the current situation of the neighborhood were obtained by field measurements, and those on the latter situation were obtained via computer simulation and addition of plants to the area. Then, the PMV model was used for assessment of the comfort conditions and specification of the exact effect of plants on microclimate elements. The two conditions were compared, and the impact of urban design with plants on environment quality was evaluated. The evaluation criteria included temperature and relative humidity. The measurements were made at a height of 1.65 meters to prioritize pedestrian comfort. The findings suggested that allocation of a low percentage of city space to greenery can greatly improve microclimatic conditions. The computations indicated that every square meter of green space added to the area under study would expand the comfort zone by 3.71 times. The results also demonstrated that retention of the amount of relative humidity can reduce air temperature by 1.5-2 degrees Celsius. The findings of this study highlighted the significance of preserving the current green spaces over the neighborhood and the necessity of avoiding any change in the land use of the remaining gardens (about 6,000 m2 in the 4-hectare area of the site). The computations also showed that addition of the existing green spaces over the area by 2.69% can expand the area within the range of thermal comfort to twice as wide as the pre-intervention area. One the other hand, the issue of global warming, the 1-degree rise in the world’s temperature during the past century, highlights the value and significance of this 1.5-degree temperature decrease. Thus, it is possible to make significant changes through extension of the results of this study to a larger scale to involve the entire city.
