Urban Sustainability
Samaneh Heidari; Golnaz Mortezaei
Abstract
Highlights The effect of some urban planning criteria on wind flow has been evaluated through a new method called Large Eddy Simulation. Simulation analysis of different scenarios confirmed that among density, lot coverage ratio and altitude, lot coverage ratio is the most influential parameter on the ...
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Highlights The effect of some urban planning criteria on wind flow has been evaluated through a new method called Large Eddy Simulation. Simulation analysis of different scenarios confirmed that among density, lot coverage ratio and altitude, lot coverage ratio is the most influential parameter on the air flow. Examining the effect of only density factor on air flow cant lead us to good conclusions about how wind flows. Fluctuations in different scenarios indicate that at the beginning and the end of the streets, the wind speed is faster than the middle. Introduction Along with the rapid growth of urbanization and the issues of global warming, environmental pollution, the urban heat island, and climate change, thermal comfort has turned into one of the most influential factors in adaptation of the design of climate-related urban open spaces. Today, the high temperature in human-made areas has doubled the need to consider thermal comfort in open urban spaces. Thus, wind flow is regarded as one of the most influential climatic parameters, where the speed and movement of the wind affect human thermal comfort. Theoretical Framework The traditional architecture and urban planning applied in the city of Isfahan, Iran makes up a unique local examples of Iranian architecture, which has been forced to provide many climatic solutions due to the hot, dry climatic conditions. In the past half century, however, a new pattern has emerged in building massing models as a result of the changes in the forms of housing space into different types of dense multi-family housing. Due to their extension and pervasiveness in Iran, these terraced housing models can be considered as part of the new urban planning trend in the country. Because of the increase in density and building surface ratios, however, part of the self-purification capacity of the urban environment has vanished, and certain construction models have become common in different climates with unfavorable conditions. As many cities are looking for solutions to apply compression and massing as far as possible, the drawbacks of the previous model have become more prominent, and a need has arisen for solutions to the current situation, in order to reduce the probable adverse consequences in the future. The consequences that may arise from this trend include a lack of thermal comfort in open urban spaces, an increase in heat exchange between indoor and outdoor spaces, and a rise in energy loss as a result. A master plan and an auxiliary force to urban designers and planners, the Booklet for Urban Planning and Building Regulations of the city of Isfahan always seeks to modify this pattern in the current situation. In the present study, therefore, attempts are made to consider the existing directions in the booklet and examine the role of physical factors in wind flow and its extent in the new fabric of the city. Methodology Due to its applied nature, this research uses the descriptive-analytical method and documentary and field techniques for data collection. Moreover, the large eddy simulation (LES) model is used for analysis of the defined scenarios. Results and Discussion. In order to achieve its purposes, the present study was designed in three phases. Thus, the effective physical indicators were first extracted through examination of the theoretical foundations related to thermal comfort, and their overlap with the directions in the Booklet for Urban Planning and Building Regulations of Isfahan was then studied. In the final step, LES was conducted through definition of the probable scenarios based on terrace housing models of the dominant line in the new fabric of Isfahan. An analysis of the simulation of different scenarios confirmed that an increase in lot coverage ratio, among the extracted indicators, caused a sharp decrease in speed ratio, while an increase in building height led to a decrease in speed ratio, and density exhibited a different effect, which could be interpreted along with the other criteria. Conclusion Based on the results, lot coverage ratio is the most effective parameter on air flow in the area, and density is not a suitable criterion for such measurement. Moreover, the effect of a change in lot coverage ratio on wind speed is greater than that of a change in building height. As for passage width, the fluctuations in speed ratio on narrow streets are far more limited than those on wide alleys and streets. Thus, speed is higher at the beginning and end of an alley than at the middle. In scenarios where building height is set between 10.5 and 14 meters, therefore, proper conditions are provided for urban air quality, ventilation, and air pollution.
Urban Sustainability
Golnaz Mortezaei; Mahmoud Mohammadi; Farshad Nasrollahi; Mahmoud Ghalehnoee
Abstract
Rapid progress in technology and, consequently, the increasing growth of urban population has inevitably led to the development of residential neighborhoods. Changes in the form of urban texture and their inconsistency with climatic features, together with the rise of energy demand, have had manifold ...
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Rapid progress in technology and, consequently, the increasing growth of urban population has inevitably led to the development of residential neighborhoods. Changes in the form of urban texture and their inconsistency with climatic features, together with the rise of energy demand, have had manifold adverse consequences such as global warming and climate change. According to previous research, most energy in cities is consumed by residential buildings which is highly affected by the city shape, an issue which needs to be amended. Therefore, since buildings account for a significant portion of energy consumption in cities, wise decisions should be made for designing new urban textures that reduce energy consumption. Research on urbanism and energy efficiency has offered different views. The vast majority of studies conducted on the optimization of energy consumption in urban areas have focused on the impact of urban shape on fuel consumption in transportation or have evaluated energy consumption in micro scales. But, as thermal performance changes in scales beyond the building scale, researchers must analyze the thermal performance of buildings in larger scales such as neighborhoods. The missing part in this field is the assessment of energy consumption in neighborhoods. To fill this gap, the present paper attempts to assess the primary energy consumption of cooling, heating and lighting systems in new patterns of residential texture on neighborhood scale. Afterwards, on the basis of primary energy criterion, efficient and inefficient patterns are identified and, finally, some strategies are provided for optimizing energy consumption in new residential areas. The present study is an applied research conducted using descriptive-analytical method. Data was collected by documentary and field methods. In the first step, the concepts of primary energy, energy efficiency, and typo-morphology approach are described and analyzed in order to formulate the theoretical framework of the research. The relationship between microclimate and morphology is also investigated. Then, following the typo-morphology approach, the residential texture of Sepahan Shahr, Esfahan, Iran, is categorized on the neighborhood scale. Finally, simulating the primary cooling, heating, and lighting equipments’ energy consumption in the residential textures via Design Builder software, results are analyzed based on the comparative approach and statistical tests. The results show that there is a strong correlation between primary energy consumption and indicators of design layout, mass placement, form of the building, height of the building, and open spaces. Also, there is a moderate correlation between primary energy consumption and block proportions. Moreover, based on the results from the variance analysis, common row patterns and square-shaped patterns are the most and least efficient patterns of new residential textures, respectively, though the lighting systems’ energy consumption is lower in square-shaped patterns. Other patterns, such as H, T, I, and L shapes are in mid-level for primary energy consumption. Among these patterns, the H-shape is the best choice for four-storey buildings with high-density.
