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A “ONE SYSTEM APPROACH” TO GLOBAL CHINESE URBAN GROWTH

A PROTOTYPE OF ECO NEIGHBORHOOD IN SHANGHAI

SERGE SALAT CAROLINE NOWACKI

CSTB URBAN MORPHOLOGY LABORATORY 84, avenue Jean Jaurès/ Champ- sur-Marne 77447 Marne-la-Vallée cedex 2

Tel: (33) 01 64 68 82 34, fax: (33) 01 64 68 89 12, e-mail address: serge.salat@free.fr

A second urban China with half a billion new urban population will be built during the next 20 or 30 years. At the present levels of efficiency and sprawl, this urbanisation process would need the resources of more than one planet Earth for China itself and would double or triple China’s entire built up area increasing tremendously transportation needs and threatening China’s food autonomy. The first question the paper will address is where to develop this new urbanisation. A compared morphological approach of densities in Chinese cities, Europe and Japan will challenge the current assumption about building new Eco cities and will pave the way to a global conception of the whole process of urban growth tapping on the potential of growth of the existing cities. The paper will then present the application to China of ‘A One System Approach’ proposed by the World Bank that enables cities to realize the benefits of integration by planning, designing, and managing the whole urban system. The One System Approach includes integrating urban ‘form’ with urban ‘flows’ by coordinating spatial development (land use, urban design, and density) with the planning of infrastructure systems. The paper will present a metrics of city forms and flows, with the development of indicators to implement this “One System Approach” in Chinese cities. Last, the paper will present a Catalyst ECO Neighbourhood Prototype project that builds on the traditional Chinese urban forms of the Jiangsu area and make them evolve towards a High Tech Eco Design. The design and technological conception of the buildings will be based on CSTB cooperation with SRIBS for Shanghai Eco Home in the Framework of Shanghai 2010 Expo. This ECO Neighbourhood Prototype Catalyst project is targeting an explicit objective of global optimisation of forms and flows and an ability (beyond its immediate project scope and objectives) to drive China’s urbanisation forward on a sustainable Eco pathway by catalyzing a process of change.

1. Introduction

Chinese cities today are facing the challenge of sustainable urbanization in front of climate change. According to the World Bank*, some 90 percent of global urban growth now takes place in developing countries. Urbanization may be the single greatest

* Hiroaki Suzuki, Arish Dastur, Sebastian Moffatt, Nanae Yabuki. (2009). Eco2 Cities, Ecological cities as economic cities. Banque Mondiale.

challenge in our century. It is projected that developing countries will have tripled their entire built-up urban area between 2000 and 2030—from 200,000 square kilometers to 600,000 square kilometers. These 400,000 square kilometers of new urban built up area, which are being constructed within just 30 years, equals the entire world’s total built up urban area as of 2000. One could say we are building a ‘whole new world’ at about 10 times the speed, in countries with severe resource constraints. We are doing so in an increasingly globalized context with many new, constantly fluctuating, interlinked, and uncontrollable variables.

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This unprecedented urban expansion places cities, nations and the international development community in front of a historic challenge and opportunity. China itself is the biggest part of the global urban challenge with the emergence of a second urban China of half a billion urban dwellers within the next 20 or 30 years. The future large-scale urban structure and city fabric morphology of Chinese cities is a key to meeting successfully the challenge of their sustainable development. Among the 4 factors leading to an increased productivity of energy, urban form is the first to be optimized.

Due to the severe shortage of land, water, energy and the severe levels of pollution attained in certain regions of China, is the creation of a second urban China possible? Should this second urban China be located as an extension of the existing one? Or should it be located within the existing one? According to current sustainability thinking, higher densities are the key to increase energy efficiency, thus increasing the density of existing Chinese cities is the key to reveal their potential of hidden energy efficiency. While transitioning towards even higher-density populations, they must also dramatically reduce their energy usage and carbon emissions. For several years now, the CSTB (The French Scientific Centre for Building Science) International Urban Morphologies Laboratory, with Chinese partners such as The University of Hong Kong and the University of Tongji, has been investigating the structure and city fabric energy performance of Chinese different urban morphologies. Our focus on Chinese cities, including Hong Kong, Shanghai, Guangzhou, and comparison with Paris, Tokyo, and Kyoto urban fabric has highlighted the issue of building mass organization in high-density situations. This paper will propose a model of urban development, presenting the assets and defaults of different urban typologies to show that dense cities of medium size courtyard blocks allow to save at least half of nowadays

consumption in energy and carbon emissions, associated with a method to link forms with flows in order to again double the savings in energy, so that China can reduce by a factor 4 to 10 according to the sectors its energy consumption and carbon emissions. Factor 4 is a concept that has been introduced by Ernst Ulrich von Weizsäcker, Amory B. Hunter et L. Hunter Lovins in their report to Club de Rome of the same name. Since the industrial revolution, progress has meant an increase in labor productivity. Factor Four describes a new form of progress, resource productivity, a form that meets the overriding imperative for the future (sustainability). It shows how at least four times as much wealth can be extracted from the resources we use. As the authors put it, the book is about doing more with less, but this is not the same as doing less, doing worse or doing without. The basis of the factor 4 thinking is that resource productivity can be substantially raised through a cascade of multiplying factors. An example is the ultra light cars with hybrid propulsion. In a normal car 99 per cent of the energy is wasted and only 1% is actually used to move the car. Only 75 % teaches the wheels and most of it is dissipated in heat. The key issue is the weight of the car, which obliges to provide very heavy motors dissipating a lot of energy. Once the weight of the car has been lowered with new materials such as carbon fiber, the technology of the motor can be changed to hybrid propulsion that recovers electronically a part of the dissipated heat in the brakes. If the weight reduction leads to a factor 2.5 increase in the energy efficiency of the car and the hybrid propulsion to a factor 2, the final result is that efficiency factors multiply and that the global energy productivity of the new type of car has been multiplied 5 fold. For cities, the parameter that has the biggest impact and corresponds to the weight of the car is density. Increased density leads to mixed uses, well connected and accessible cities that reduce the need for car transportation. As we will see, the energy needs for transportation and for heating of cities and thus their carbon emissions are inverse functions of their densities. Multiplying the densities by 4 divides by itself the energy needs by 4 and thus multiplies by 4 the richness and wellbeing created by a unit of energy spent in the city. But this is not the only advantage of density. As with the ultra light car, the dense city can shift to a different technological paradigm, moving from

Figure1:The factors influencing the energy-efficiency of cities

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hierarchical systems such as huge remote power stations with tremendous losses during the transportation of energy to distributed, locally produced renewable energy. Density allows for closed loop metabolism and cascade use of resources that will be described in this paper. We will show that density and urban form can account to a factor 2 to 4 by themselves, building technology to a factor 2.5, the efficiency of energy systems to a factor 2 and people behavior to another factor 2. By multiplying these factors that act in synergy, the global energy productivity of the city can be multiplied by 10, creating wealth and well being while keeping in planet Earth global limits. Finally, we will illustrate these theories thanks to a prototype of neighborhood, and present its features and environmental performances. 2. Achieving redevelopment of existing city

through adapted dense morphologies

2.1. The importance of city fabric on the energy efficiency of Green Buildings

The stakes are high for reducing cities energy consumption and carbon emissions, and every influential factor must be considered. An integrated, global approach to sustainability, based on the synergy of multiplying factors, drawing upon both the disciplines of science and design, is needed to achieve the maximum energy-efficiency of Green Buildings. The CSTB (The French Centre for Building Science) has responded to this global call for sustainability through a strong, long- term cooperation with the Chinese MOC, leading to the publication of the Sustainable Design Handbook China in 2006, and cooperation with Chinese major municipalities including Tianjin in 2002 and Shanghai from 2007. We need first to present the importance of city fabric in achieving sustainability and energy-efficient building performance. The CSTB Urban Morphologies Laboratory has launched a research program for measuring internationally the key parameters of urban morphology in order to define the most efficient forms for low carbon cities (building forms and sizes; street patterns; urban and building design). This study of urban fabric is a mean of discerning the underlying structure of the built landscape and the impact of morphologies on the energy efficiency of cities. It

involves mapping and describing patterns of land use. Urban morphologies are related to energy and carbon efficiency through the organization of the building mass, the street network, and the density. Urban Morphology is an influential factor on the energy performance of a city building stock that has unfortunately received little attention in comparison to other ‘greening’ strategies. However, with research showing that urban morphology alone has an impact on energy performance of the order two to four, it is a lever of change too large to ignore.

2.2. Transportation energy and the importance of density in the energy performance of cities

Density is the key factor in the energy performance of cities both through transportation energy and through urban typology. The first key aspect of energy-efficiency of the urban fabric is transportation energy. Transportation energy is linked to density by a simple law. The Newman-Kenworthy curve shows that the amount of transportation energy is an inverse function of demographic density: E=k/D. This law implies that the amount of energy spent in a metropolitan region varies with the square of the size of the region. In other terms, a metropolitan region whose span is 5 times larger than another one will tend to use 25 times more energy.

Figure 2: The Newman-Kenworthy curve linking demographic density and transportation energy In the following parts of this paper we will use the concept of urban density which is the ratio of the total number of built square meters divided by the entire surface of the site including public spaces and roads. Plot ratio does not describe correctly the urban form as in traditional European urban fabric the building

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footprint on the site can be as high as 65% while in American sprawl or modernist urban fabric it may be lower than 10%. In modernist utopian visions such Le Corbusier’s city of 3 million inhabitants, the ground was left empty for the enjoyment of city parks. Sadly in reality, the space between buildings has been occupied by giant highways and turnpikes and by immense parking lots. In most parts of Paris the urban density is between 4 and 5, while in Shanghai or Guangzhou it is around 1 at neighborhood scale and much lower at global city scale. Now the level of motorization in Shanghai is extremely low (5.9%) but due to the improvement of living conditions and to the sprawled form of the city, it may reach in the future the same level as Los Angeles (80 %). Just due to the huge size of the urban region, the energy of transportation per inhabitant in Shanghai will then tend to be 5 to 10 times higher than in the dense cores of European cities. Already an 8 to 16 fold difference in car-energy use can be observed between some dense Asian cities such as Hong Kong, Seoul, and Tokyo, and the sprawled West-coast cities of America such as Los Angeles.

2.3. Urban typology and density

The different levels of density are statistically associated to different urban block typologies. As explained below, urban density does not equal verticality. In fact modern vertical urban forms are 4 to 5 times less dense than traditional European urban blocks. The explanation is very simple. In Paris, 65% of the ground is built with 7 floors buildings. If we divide the occupied space on the ground by 6,5 to obtain 10% of the ground occupied as it is in Pudong, in order to obtain the same density, we need to multiply the number of floors by 6,5, which leads to building towers of 45 floors. We checked this results by analyzing numerous Chinese urban fabrics. To describe the relationship between density and urban form, we will rely on the work by Agma “density and urban forms in the metropolis of Marseille”. In this book density is measured at the buildings block scale using the FAR (floor area ratio). Six urban forms, called “housing categories”, are analyzed:

Figure 3: Three typologies of urban forms • Scattered detached houses FAR = 0,04 • Pavilions FAR = 0,25 • Traditional village FAR = 1,5 • Terraces FAR = 1 to 1.2 • Courtyards 4 to 7 floors high FAR = 5 • Slabs and tower blocks FAR = 1,25. Detached houses are the less dense urban form. The density of a traditional village is identical or even higher than the one of some slabs and tower blocks, high but scattered. Again we see that density does not correspond to verticality. The traditional courtyard of 4 to 7 floors is the urban form creating the higher density. Slabs and tower blocks are generally 4 times denser than pavilions, and traditional courtyards are 4 times denser than slabs. This leads to a factor 16 of densification between pavilions and traditional courtyards. ! Statistically, densities are associated with specific typologies of forms. To achieve the higher density, the most appropriate urban form is the one of the traditional courtyards, like Haussmann courtyard blocks in France, and not the modernist isolated high rise forms. These variations from 1 to 16 depending on urban forms have sizeable consequences on energy consumption. Jean Pierre Traisnel studied this energy consumption for 3 typologies recurrent in Ile de France.

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Figure 4: The progressive loss of density in Ile de France from 1900 to 1969, to 1990 The first typology corresponds to the centre of Paris made of dense traditional medium size courtyard blocks. They date back from the past century and are not well isolated, yet their heating consumption is not so high because the exterior envelop surface is reduced. The second typology is a slab built in the sixties with a large surface of windows, the surface of loss is higher and it is located in suburbs with very few public transports and mixity. The third one groups pavilion built recently in a suburb of Paris. There are very few public transports there. Though its houses have been built recently and benefits from a much higher isolation of the walls and roof than the two other typologies, its needs for heating are basically 30 to 40% superior to isolated collective housing. The new pavilions use as much heat as the buildings of the past century which are not isolated. The first typology allows to create a dense urban fabric, with a mix of activities and good connections by public transports. This is why transfers account only for 25% of the total consumption of energy of their inhabitants, versus 50% for the pavilions and slabs. Total energy consumption for a new construction in the centre of Paris is of 800 MJ/m2.year versus 1300 MJ/km2.an for a new pavilion (+60%) and more than 2000 MJ/km2.year for an old pavilion. Unless by reducing individual transfers, which is not possible due to the form and organization of the suburbs, it is impossible for pavilions to be as energy efficient as courtyard blocks in the town centre: they would need to have 0 loss through the envelop. Carbon emissions due to transfers in the suburbs are 2 to 3 times higher than

emissions for heating in the suburbs. Moreover they are twice higher than the emissions of the centre of Paris. The emission rate in new slabs in the suburbs is 40% higher than the one of Paris. When considering energy consumption for buildings only, it is 20% higher in the suburbs in comparison with Paris. This shows that new technologies cannot be a solution alone since someone living in a very well isolated pavilion creates twice as much carbon emissions as an inhabitant of a renovated old building in central Paris. Urban forms are a sizeable factor in energy efficiency and the CSTB urban morphologies laboratory works on finding the measurable factors to describe the relationship between the two.

2.4. A measurement of parameters describing the interaction of the city fabric with its environment

Figure 5: Four sets of morphological parameters influencing the energy efficiency of the city fabric

1. Building mass organization (built-up area, FAR, contiguity, building height, compacity…)

2. Openness to the sky (occlusivity, solar admittance)

3. Passive volume (that is the volume less than 6m from the envelope)

4. Street networks Through Urban Morphology Analysis, it is possible to calculate the underlying morphological parameters of a given area, including: compacity, porosity, proportion of passive zone, built form density, and solar admittance. By selecting various samples of urban fabric in a particular city, calculating their morphological parameters, and associating these with their respective energy consumption, it has then been possible to determine the energy-efficiency of different urban textures: the most relevant parameters; and their respective impacts. Further analysis of a city fabric’s street network provides a measure of the connectivity and diversity of

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choices of routes in the area. Various characteristics can be calculated such as: density of streets; density of intersections; distance between intersections; and the average number of connections between two points (cyclomatic number). These results indicate an area’s degree of connectivity and accessibility, and can then be used as indicators for traffic flows and congestion, and the resultant fuel-usage and pollution effects. The results can be used to inform more energy-efficient urban development by: identifying the most /least efficient urban areas in the city and thus areas requiring priority attention; assessing the urban growth potential of selected sites and identifying areas for low-impact development; assessing the energy performance of development proposals; and guiding the design of future urban developments. The benefits of such an analysis to a city’s urban planning policies and strategies are great, with the possibility to: evaluate current design guidelines for their energy performance; inform more ‘energy-efficient’ urban design guidelines; and assist in the calculation of a set of sustainability indicators for the city.

2.5. The urban fabric in Asian, Chinese and European cities

We have analyzed the entire city of Paris, the entire cities of Tokyo and Kyoto at different periods of time, and 10 to 40 urban square frames of 800m*800m for each of the other cities. This database of 10,000 different urban textures has much to tell about the sustainability of these various urban fabrics. Paris, Kyoto, and the ancient fabrics of Guangzhou and Shanghai, have very similar parametric profiles. Hong Kong is different (2 times denser than Paris in built form and 10 times higher in building height with severe problems of solar admittance, stagnation of pollutants and heat island effect, that show the limits of achieving high-density through very tall buildings). Some high-rise districts of over 45 floors, in Shanghai and Hong Kong, have similar or lower urban densities than 7 floor neighborhoods of the historical centre of Paris. This was predictable for geometric reasons and because of land use, but still remains a very striking result: very high rise is in reality medium or low density even if it is perceived as imposing and dense

This has important effects on the sustainability and adaptability of this type of vertical urban fabric.

Figure 6: Kyoto low-rise areas of 2 to 5 floors, have the same density as Shanghai areas of 10 to 25 floors, while Guangzhou recent developments need to multiply the building height by 10 and reach 30 floors to multiply only by 2.5 the density of low-rise Kyoto.

2.6. Building mass and street grids: the effect of a fine-grained texture of small buildings versus large-scale buildings in a larger, loosely-connected urban grid

Street patterns are also very different among the studied cities. We have used the theory of graphs to assess the efficiency of street networks. An important parameter among others, the cyclomatic number (the number of different paths between 2 points in a network) is high in Paris, Hong Kong, Kyoto, Tokyo and the ancient parts of Chinese cities but is divided by 15 in the new Chinese developments The average distance between intersections is more than 3 times higher in Guangzhou CBD than in Paris, while the density of intersections is 10 times lower in Guangzhou than in Kyoto. There appears a clear pattern of urban types. On one side Kyoto and Tokyo have a very finely grained street pattern with an average distance between intersections of 50 m and very high levels of connectivity (cyclomatic numbers higher than 90 and going up to 150). The street pattern in Tokyo is organic and follows the topography, while in Kyoto the square shapes of the neighborhoods (chô) are a 1200 years old heritage of Heiankyô, planned in 794, and inspired by the Chinese

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Chang’an capital of the Tang dynasty. Nevertheless the mathematical analysis of the street grid reveals the same underlying structure in both Tokyo and Kyoto, planned almost 1000 years one after the other. Both are typical walking cities in Asia, influenced by Chinese culture.

Figure 7: Three very different patterns of street grids In the middle stands the XIX th century European fabric, with striking similarities between Paris, Hong Kong and the centre of Melbourne, all planned by Europeans. The average distance between intersections is usually 150m and the cyclomatic numbers range from 60 to 90. These cities were planned as walking cities and provided with good public transport. At the other end are contemporary Chinese developments showing huge distances between intersections (between 500m and 600m) and very weak levels of connectivity, with cyclomatic numbers around 6 (thus 15 times weaker than in Europe). These street patterns are typical of car-oriented cities.

2.7. The new Chinese urban fabric: a new model of high-rise buildings characterized by low or medium overall built density with huge urban blocks loosely connected.

These findings challenge many current assumptions about the density of modern Chinese cities. They appear like a new model of high-rise buildings. This model is nevertheless characterized by low or medium overall built density as there is a lot of empty space between towers. Thus huge urban blocks are loosely connected with highways. This has a strong impact on their sustainability that needs to be thoroughly investigated.

The city fabric is a key driver to ensure the global sustainability of these Chinese cities as shown by the studies we have undertaken. The transition of the Chinese city fabric towards a radically new model needs to be investigated. 2.8. Traditional medium rise and connected

urban blocks are more energy efficient than isolated high rise buildings

To summarize, our analyses have shown that for both lighting and thermal comfort energy (the parameters of compacity and passive volume) as well as for transportation energy, the compact, low-rise urban blocks of traditional European cities are more efficient than recent low-density, high-rise Chinese developments by at least a factor of 4. The only reason why Chinese cities do not spend 4 times more energy than European cities is the low level of motorization in China and the relatively low level of thermal comfort. However, with an increase in motorization and in the criteria of comfort, the car-oriented large-scale and loosely-connected patterns of contemporary Chinese urban fabrics have the potential to lead to an explosion in energy demand. Therefore, improving the design of Chinese cities fabric and orienting it in the direction of more compact transit-oriented development, is key to the future sustainability of Chinese cities. 3. Optimizing forms and flows: multiplying by 10 to 25 the productivity of resources in cities Our studies have shown that the combination of all influential families of factors of energy-efficiency at urban scale can lead to a 25-fold difference in energy consumption. Among them, the efficiency of the urban fabric is an important one.

Figure 8: Combination of the 4 sets of influential factors

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This huge multiplying factor in energy and resource productivity is the result of the multiplication of smaller sub factors, which create a great effect when put in synergy. Thus we need to examine now the technological factors of urban energy efficiency, which can multiply the positive effects of urban density

3.1. A one system approach

We just showed how adopting a dense city with medium rise buildings could halve or divide by 4 energy consumption and carbon emissions. That was working on the form of the city, but what is linked and subsequent is that all sorts of flows are dependent on forms, and that building a city without including and coordinating the flows inside the forms will prevent from benefiting from another reduction by two of energy consumption. In fact, implementing new systems and technologies for flows of water, energy, people and waste can also halve energy consumption and so carbon emissions, but it is important to keep in mind that this will be much more efficient if the form of the city is adapted and that dividing by 2 or 4 through densification and choice of optimum morphologies and dividing again by 2 by efficient technological systems does not lead to dividing by 2 but to dividing by 8. Factors multiply their effects

That is why new working methods must be adopted in urban planning, as reminded the World Bank this year in its book eco2 cities. In fact, all actors of the city must work together to conciliate morphology and technologies. To do so, some tools are very efficient and should be adopted to plan cities and to measure their performances.

3.2.Integrating flows with Infrastructure System Design and Management

Figure 9: integrating forms and flows, source: World Bank, eco2 cities

All the sectors of flows in the city: transport, energy, water or waste management can be optimized by applying some simple tools. First, when considering demand and supply, it should be thought of the possibility to invest to lower demand instead of building new infrastructures to answer it. This is illustrated with the problem of transports: to answer problems of cramped roads, it is better to try to build more pedestrian ways and to facilitate travelling by bike, rather than to build more roads, which would not completely answer the problem and deteriorate the environment. Here the correct answer was to reduce the need for cars instead of supplying the demand for more cars and roads. It can be applied to heating too. If demand for energy for heating increases, instead of building a new plant, it would be better to improve the insulation of the buildings in order to lower the demand, allowing the same comfort for the inhabitants but for a smaller production of carbon. Second, the problem of peaks of demand and the means to answer them should be resolved by performing Peak load management. All sectors, transport, water, energy, and even space suffer from daily or seasonal peaks of demand which results in oversized systems and external

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supplies. A specific attention must be paid to these problems to find the better alternative solutions. Third, resources must be reused and forms should allow systems permitting cascading resource use and looping resource use. At the scale of the house or of a block, cascading resource use is achieved by matching the quality of a resource to the requirement of the end user. It can be applied to water: clean water is used in the kitchen and then the used water is redirected and reuses for the toilet flush or in the garden. At the city scale, an example can be the burning of waste to produce energy. Looping refers to the closed looped systems that ultimately return water and materials to their point of origin. We can think of a house that treats with special planted gardens the water it uses and can so reuse it after local treatment. Hierarchical, unidirectional systems should be replaced by distributed systems for omnidirectional flows. The aim is to reduce the distances of transports of energy, water, and so on, responsible for a lot of waste of the resource. Each part of the town, sometimes even each building should be productive and answer a part of its needs. Placing photovoltaic panels on buildings can allow them to benefit from their own resource of energy, but with our omnidirectional system, it can do better: it can also provide energy to other buildings around which would need energy not used by the producer. Producing locally and giving the possibility to share between a lot of producers reduce risks of lack and reduce waste.

3.3. Spatial planning and urban design to integrate flows in forms

Buildings can be designed to be used differently at different time of the day or of the season. This would be a gain of space. For example, a school can be a market place on the week end and a theatre in the evening. When building a block, it should be thought of the way the building will treat its used water and recycle waste, along with planning solutions which can be implemented locally. A compact city which is not sprawled and fragmented at the scale of the urban region will use a smaller length of canalization and minimize the waste of resource.

Nature and natural systems should be better used thanks to the city form. Medium size buildings with courtyard allow not making too much shadow on others and integrate multiple social spaces. The courtyard can be used for plenty of things such as green spaces for treating water, but also places of leisure for the inhabitants, protection from sun in summer… Green spaces are very important because they play multiple roles. They gain to be everywhere in the city, in long green corridor along axes of transfers, in courtyards, private or public, and in parks. In fact, plants allow to capture carbon, it can so help to diminish its quantities in the city and then in the atmosphere. They also produce shadow and fresh air during summer, thanks to their leaves. During winter, trees lose their leaves, allowing the light to pass. They are so really useful near the roads and form agreeable paths for pedestrians and bike. They can sobe an incentive for people to walk or ride a bike, since green paths are more pleasant and less dangerous than ordinary roads. Finally they also help holding the soil and prevent mudslide, which is more and more often a problem today.

4. A prototype of eco neighborhood in Shanghai area

4.1. Structure of the prototype

We focused on a neighborhood of 800m x 800m, which we decided to place in Tong Li, so in the surroundings of Shanghai, with the specificities of its climate and environment. This space of 640 000 m2 is divided between different uses so that 10% represents the canals naturally present on the site, 15% are dedicated to roads, 35% are buildings and 40% are green spaces. The buildings are contiguous and with a mean of 4 floors each. They are open on courtyards, which represent 25% of the site and shelter green spaces. So blocks are equally divided into buildings and green spaces creating a pleasant feeling for the inhabitants. Thanks to medium rise buildings, we achieve a high density of 250 inhabitants per hectare and 150 jobs per hectare. By comparison, there are 201 inhabitants per hectare in Paris. There is so 16000 inhabitants and 9600 jobs in this neighborhood.

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Figure 10: Blocks with courtyards and green spaces

4.1 . Mixity and movements

Mixity of uses and spaces is a very important factor to allow that all basic needs and even work can be accessible by walking or riding. This neighborhood is entirely made for moving without cars whose access inside is restricted. Streets are reserved for public transports, pedestrians and bikes. Cars are kept in car parks outside the neighborhood. We so hope to minimize carbon emissions without restricting people movements. A dense net of public transports is settled: a tram station is reachable at most at 600 m from every point of the city. Place to keep bikes are also planned in buildings and public spaces. Canals are used to transport goods and waste. Thanks to this mixity, no places are desert during some times of night or day which makes the neighborhood livable and attractive. Moreover it creates a pleasant feeling of knowledge of places and people thanks to the small businesses where people do shopping and the walking streets.

4.2 . Water management

Water is partially treated locally, at the scale of the block, thanks to planted gardens. Rain water is kept in pools in the courtyards and can be used for toilets or to provide plants with water. Drinking water from a water purification plant is available in the house for the kitchen, then it is reused for toilets and then treated in the pool of the courtyard. This treated but non drinking water is reused for shower, toilets, and washing machine.

4.3 . Energy

Needs for heating in winter and fresh air in summer are reduced thanks to a good isolation and intelligent placement of the windows and opening of buildings, along with the management of winds through the streets and the freshness brought by the trees. The buildings have almost only passive volume and only need artificial light at night. Thanks to all that, the amount of electricity needed for heating water, electricity, heating and cooling in the neighborhood should not exceed 45 GWh of primary energy per year. A part of the electricity would be produced by photovoltaic cells placed on the roof of the buildings. Another part will come from systems of heat recuperation from the plants.

4.4 . Waste management

Waste would be sort between organic and non organic first by the inhabitants. Organic waste would be taken on the canals to incineration plants to make electricity. A more precise selection would be made by people for plastic, paper and metal, collected by workers with bicycles from recycling plants.

4.5. Carbon footprint and Eco foot print We aim at having a carbon footprint near zero as have other eco neighborhood like Malmö in Sweden or Bed Zed in United Kingdom. This is possible thanks to 90% of the transfers performed by modes non producer of

Figure 11: Looping resource use

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carbon (pedestrian, bikes, electrical tram with green electricity). We try to lessen the demand in energy so that green methods of production can provide it for the neighborhood. Then the 40% of green spaces help absorb a part of the CO2 produced.

5. Conclusion

Nowadays, cities assess the economic value of their projects by calculating the short term return on investment, and earnings are often judged adopting the point of view of a unique actor. Investments are only computed in monetary terms, and what cannot be put a figure on easily is put aside. Investment decisions are dominated by immediate cost of capital whereas 90% of the lifetime project costs come from operations of maintenance. This non consideration of the project lifetime creates critical debts for generations to come. Natural goods are often ignored because they are hard to put a figure on. Nonetheless, they are a true asset thanks to the numerous services they provide which can substitute some industrial services, as drainage or temperature lowering, thus representing a monetary value. Therefore, we suggest adopting new projects assessing methods in order to consider long term earnings brought by eco friendly solutions. The aim is to encourage investments that have favorable results for all the city actors, that preserve all the assets (industrial, human, social, natural), and that lead to a fiscal good health. Risks must also have a place in the assessment, to draw a portrait close to reality, and to allow predictions and protections of the cities from natural disasters which could become more and more frequent in the near future. Finally, new indicators and benchmarks, as the lifecyle costing advised by the World Bank, should be adopt in order to have a truer idea of the value of an investment, which cannot spare the long term vision. We would like to conclude on the fact that eco friendly measures are not only necessary but are a real opportunity to save money. The methods we proposed allowed reducing by a factor ten energy consumption and carbon emissions, that means saving money for the creation of energy plants and for the treatments of the bad environmental effects they have, without necessarily make the growth stop since other green solutions, much more valuable and creators of money

develop at the same time. Growth can be achieved by putting aside old polluting systems and letting develop new systems. Lowering carbon emissions now means saving the money which would be necessary in the future to reduce it and whose amount is increasing with the amount of carbon emitted. Inversing processes are much more costly than acting at the beginning that is why applying eco friendly measures now will cost less money than in the future and will allow immediate savings thanks to the factor 10 lowering.

6. Bibliography

AGMA. (2005). Densité et formes urbaines dans la métropole de Marseille. IMBERON. Hiroaki Suzuki, Arish Dastur, Sebastian Moffatt, Nanae Yabuki. (2009). Eco2 Cities, Ecological cities as economic cities. Banque Mondiale. Jean Pierre Traisnel. (2001, avril). Habitat et développement durable, bilan rétrospectif et prospectif. Les cahiers du CLIP, n°13 . Ernst Ulrich Weizsäcker, Amory B. Lovins, L. Hunter Lovins. (1997). Factor four: doubling wealth - halving resource use, Earthscan.