**1. Introduction**

#### **1.1. Urban climate change in cities**

In recent years, urban climate change has been observed in most of the world's developed cities. In central Beijing, the annual air temperature rose 0.36°C during 1961–1980. However,

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

during the building boom between 1981 and 2000, it rose 0.94°C [1]. The correlation coefficient between the impervious surface rate and land surface temperature in Beijing reached 0.93, which means the impervious of urban surface is providing a large contribution to urban climate change [2]. Climate models indicate that due to the expected warming of up to 9°C by the 2080s in the Arctic and the southern and central Prairies [3], the number of days with average temperatures above 30°C is likely to increase in cities across Canada, especially those in the Windsor-Quebec corridor (such as Toronto) and portions of British Columbia. Thus, urbanization patterns, especially in the central parts of cities, have a large impact on urban climate change. The spatial variability of urban heat islands (UHIs) in cities has been found to be a function of urban surface properties, which in turn are influenced by land cover, especially vegetation cover and building density [4].

The deep urban canopy created by high rises can increase the wind speed in urban areas and affect the urban thermal environment. A simulation comparison of high-rise and low-rise buildings in the Lujiazui district of Shanghai found that with low-rise buildings, wind speed declined 22%, air temperature decreased 7%, and O3 decreased 9% [5]. Another study used wind tunnel measurements to examine wind velocities in Toronto, confirming that among several high-rise towers, wind often accelerated above 10 m/s; this created wind-chill effects and exerted mechanical forces on pedestrians, making it unsafe for them to walk [6]. The openness of urban geometry can be defined using the sky view factor (SVF). The correlation between SVF and the urban thermal environment has been demonstrated in Montreal, Canada [7–9]. A high SVF, which means more open urban space, could be related to a lower UHI index.

After the high-speed urban expansion, real estate developers started to have a major impact on urban reform after 1990s. New large-scale developments started occurring outside the city core. During this period, the sense of building design and construction quality became more important than that in the past. High-rise and detached houses were also developed in some

Urban Renovation and the Simulation Evaluation of Urban Climate Change in Residential…

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63

After 2000, because of the increased population density, the high-rise building has become the most common construction style in residential development projects. The first demand of residential construction has shifted from meeting the citizens' living to promoting real estate and the urban economy status. The process of urban expansion in Xi'an is showed in **Figure 1**. It is clearly showing that urban occupation has grown rapidly during 2000–2010. Meanwhile, urban building density has also increased because of the high building density of

Residential building is the most typical form of architecture in the city as some related research points out. From 2000 to 2010, area of residential land accounts for the largest proportion in urban land use type [12]. In this study, typical urban planning styles in China were selected and analyzed. Microscale residential districts in Xi'an were selected for representing the typical urban typology of residential districts that developed during different periods and used the urban simulation system scSTREAM (Software Cradle Co., 2011) to evaluate the impact of

To estimate the impact of urban typology to urban ventilation and urban air quality, four typical residential areas were selected. The first area, Sanxuejie, is a low-rise area, a traditional residential zone rebuilt after the 1950s. It retains the urban form used in China Science the Ming and Qing Dynasties (about 600 years ago), with narrow streets between residential buildings, most of which have two floors. The second area, Xitiedaminggong, is a middle-rise neighborhood developed in the early 1990s. All of the residential buildings are five floors in

of the projects, and most buildings were still 5–7 stories.

urban typology change on urban climate change.

**2.1. Urban typology in Xi'an city**

recent development projects.

**Figure 1.** Urban expansion in Xi'an [11].

**2. Methods**

Urban development largely serves the purposes of economic development. Especially in China, large-scale, rapid urban development mostly focuses on the operational efficiency of cities, with little attention to the long-term environmental effects. This is a major cause of China's current environmental crisis, and the problem is rapidly spreading to India as well as other countries of Southeast Asia and the Middle East.

#### **1.2. The urban typology changes of cities**

With the accelerated speed of urban development and the constant expansion in Chinese cities, the urban typology has undergone drastic changes in the past 10 years. Xi'an is a historical city as well as one of the most developed cities in China's central plains, which is experiencing rapid urbanization development, urban renewal and expansion. Most of the current urban buildings were constructed after 1979 [10]. Different development styles and residential building types can be observed for the different periods of rapid urban development. The urban typology changes of Xi'an is the epitome and representative that of China.

In China, the government started to pay attention on economic development and infrastructure redevelopment after 1979. In the process of redeveloping existing urban areas, new construction was continuously built on the edges of central urban areas. In order to meet the residential demand for citizens, large factories led to developed residential communities around the factories for their staff and workers. During this period, most of the buildings are built in 5–6 stories, and some of these have seven floors.

Urban Renovation and the Simulation Evaluation of Urban Climate Change in Residential… http://dx.doi.org/10.5772/intechopen.79267 63

**Figure 1.** Urban expansion in Xi'an [11].

during the building boom between 1981 and 2000, it rose 0.94°C [1]. The correlation coefficient between the impervious surface rate and land surface temperature in Beijing reached 0.93, which means the impervious of urban surface is providing a large contribution to urban climate change [2]. Climate models indicate that due to the expected warming of up to 9°C by the 2080s in the Arctic and the southern and central Prairies [3], the number of days with average temperatures above 30°C is likely to increase in cities across Canada, especially those in the Windsor-Quebec corridor (such as Toronto) and portions of British Columbia. Thus, urbanization patterns, especially in the central parts of cities, have a large impact on urban climate change. The spatial variability of urban heat islands (UHIs) in cities has been found to be a function of urban surface properties, which in turn are influenced by land cover, especially

The deep urban canopy created by high rises can increase the wind speed in urban areas and affect the urban thermal environment. A simulation comparison of high-rise and low-rise buildings in the Lujiazui district of Shanghai found that with low-rise buildings, wind speed

wind tunnel measurements to examine wind velocities in Toronto, confirming that among several high-rise towers, wind often accelerated above 10 m/s; this created wind-chill effects and exerted mechanical forces on pedestrians, making it unsafe for them to walk [6]. The openness of urban geometry can be defined using the sky view factor (SVF). The correlation between SVF and the urban thermal environment has been demonstrated in Montreal, Canada [7–9]. A high SVF, which means more open urban space, could be related to a lower

Urban development largely serves the purposes of economic development. Especially in China, large-scale, rapid urban development mostly focuses on the operational efficiency of cities, with little attention to the long-term environmental effects. This is a major cause of China's current environmental crisis, and the problem is rapidly spreading to India as well as

With the accelerated speed of urban development and the constant expansion in Chinese cities, the urban typology has undergone drastic changes in the past 10 years. Xi'an is a historical city as well as one of the most developed cities in China's central plains, which is experiencing rapid urbanization development, urban renewal and expansion. Most of the current urban buildings were constructed after 1979 [10]. Different development styles and residential building types can be observed for the different periods of rapid urban development. The

In China, the government started to pay attention on economic development and infrastructure redevelopment after 1979. In the process of redeveloping existing urban areas, new construction was continuously built on the edges of central urban areas. In order to meet the residential demand for citizens, large factories led to developed residential communities around the factories for their staff and workers. During this period, most of the buildings are

urban typology changes of Xi'an is the epitome and representative that of China.

decreased 9% [5]. Another study used

vegetation cover and building density [4].

62 Sustainable Cities - Authenticity, Ambition and Dream

UHI index.

declined 22%, air temperature decreased 7%, and O3

other countries of Southeast Asia and the Middle East.

built in 5–6 stories, and some of these have seven floors.

**1.2. The urban typology changes of cities**

After the high-speed urban expansion, real estate developers started to have a major impact on urban reform after 1990s. New large-scale developments started occurring outside the city core. During this period, the sense of building design and construction quality became more important than that in the past. High-rise and detached houses were also developed in some of the projects, and most buildings were still 5–7 stories.

After 2000, because of the increased population density, the high-rise building has become the most common construction style in residential development projects. The first demand of residential construction has shifted from meeting the citizens' living to promoting real estate and the urban economy status. The process of urban expansion in Xi'an is showed in **Figure 1**. It is clearly showing that urban occupation has grown rapidly during 2000–2010. Meanwhile, urban building density has also increased because of the high building density of recent development projects.
