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Timber for Low Impact Buildings --Material for Low Impact Buildings Name: Chenlu Ouyang Course: ARC6821 Tutor: Lucy Jones Registration No: 110118622 1 Timber In Low Impact Buildings —— Materials for Low impact Building Essay Type B Abstract: The climate change and energy crisis require more sustainable buildings than before. Timber is a traditional building materials which is eco-friendly and sustainable and can be used for the modern sustainable architecture. This essay describes some of the traditional and modern ways constructions of timber buildings. Then discuss the possibilities to adopt this material in my hometown of Hunan Province in China. Key words: sustainable, local, renewable, recycle, climate 2 Introduction: Due to the climate change and energy crisis, now “sustainable” has became the theme of this time. Architecture is one of the important part of energy consumption, and it needs to be much more sustainable than before. Some modern materials such as concrete and steel seems can not meet the requirement of sustainable. In order to minimize the environmental impact of the buildings, by embodying the low impact building materials is very helpful especially in minimizing the energy and carbon dioxide emission. There are many kinds of low impact building materials such as straw bales, rammed earth, compressed earth blocks, hemp-lime blocks, timber. In this essay I will discuss timber as a material for low impact building and also discuss some new technology of timber construction and the management of the manufacture for timber and timber component. General description of timber: Timber is one of the oldest building materials which has been widely used worldwide from ancient time. It is a natural, renewable material and very easy to use. Timber products can store more carbon dioxide, and will continue to store it throughout their longsevice life, than the carbon dioxide emitted during their process of manufacture. According to the natural characteristics of timber, it is strong in both tension and compression and has a high strength to weight 3 ratio. Almost any size of design structure can be made by timber. Another important characteristic of timber is that it is light and versatile, so it can be used not only for the structure, it can also for interior or façade, including framing, lining, cladding, flooring, roofing, covers almost every parts of buildings. Traditional use of timber: The use of timber in architecture can be dates back to thousands of years ago. In China, timber structure was in the dominant position for ancient times and used extensively in traditional architecture. It starts from the house in the southern part of China that has a humid climate and rich in timber resources. Then different form of the timber buildings developed and been widely used in different kinds of architecture such as palaces and temples. This may due to the traditional Chinese philosophy that the ancient Chinese believes in reincarnation, and timber is the kind of the material that has an endless cycle and represent a symbol of eternal life. Though compared to stone, timber is weaker in ruggedness and durability, and it will also be Ancient timber structure of China limited in the natural size of trees. 4 So the ancient timber buildings were usually one or two stories. While the craftsman has developed a construction system to make full use of the flexibility of timber. The main structure of timber building was beam and column system, the main loan-bearing part is the column and beam, the wall works just as the retaining structure. In this way even though the wall falls down, the building will not collapse. This endows the building a good seismic performance. A complete set of timber construction system has been developed after thousands of years. At the same time, a module co-ordinator system is developed. Different components of the timber structure were made according to the specific module. Mortise and tenon: The most common traditional construction techniques for timber architectures is the mortise and tenon. This technology may be developed because of the natural characteristics of easy to cut and handle of timber. The most simple and basic mortise and tenon Generally, the mortise and tenon joint is the method to join timber by working a solid rectangular projection in the one piece and cutting a corresponding cavity to receive it in the adjoining piece. There are different kinds of mortise and tenon, and in China, this 5 technique has been developed to extreme, it is not only for the purpose of structure, but also a way of decoration to show the natural beauty of timber. Modern use of timber: The development of timber architecture had been stopped for a period of time. This may due to the development of technology and the contemporary construction especially after the industrial revolution, new material such as steel and concrete has become the main building material. Another factors is the deforestation caused by inappropriate logging that prevent the development of timber construction. But great quantities of energy or other resources will be consumed during the process of the modern construction operation and eventual demolition of buildings that is made by some modern materials. Take steel as an example, the manufacture of steel burns non-renewable fossil fuels and releases about 2 tonnes of carbon dioxide for each tonne of steel produced. With the increasing awareness of environmental issues, such as the energy crisis and climate change, much more concern has been made to the environmentally sustainable development, especially into the environmental performance of buildings. Timber, which is readily available and easy to work can be redeveloped as the sustainable and natural building material for modern architecture. Another advantage of timber is that it can store the carbon and has a low embodied energy. 6 Obviously, the traditional way of timber construction can’t meet the requirements of the modern needs, and some natural weakness of timber should be overcome. So some new technology of timber developed. One important progress of timber construction is that to combine it with some other modern materials. For example the joint of timber now has combined with steel component to make it more stable and have a better seismic performance. The timber component will have a series of special to enhance the ability of fireproof, moistureproof and anticorrosive. In traditional timber buildings, the majority way to use timber was to use it to make the framework. While the function and form of modern timber has become more diverse than ever before such as timber panels, timber strings, etc. It can be used in different aspects of buildings. In the large commercial building of One Omotesando which was designed by Kengo Kuma, the structure is made of steel, the timber works as the decoration both interior and exterior. In this way , nature has been bring to the urban space. The purpose of this project was to relocate the sociation in Tokyo, in order to better display the various possibilities of timber, and in the hope of reviving its popularity as an urban construction material. 7 8 Prefabrication of timber: The traditional way of timber construction is mainly handcrafting. It is extremely detailed, and needs exacting precision and craftsmanship. But this way of manufacture which needs intensive labour and will take a long time that can’t meet the requirement of modern timber construction. One of the solution is that to automate the production process, it is also very important to continue the timber construction. To use the precut technology for timbers, crafting the holes, pegs, and jointing by modern machinery for frames in the building industry. The precut system produces accurate sized timber frames. Logged woods warp, twist and shrink when moisture evaporates. One of the successful examples of the prefabrication timber house is the Japanese Onjuku beach house. It is a example of the fully automated technology. It was erected only in 1 day by a small construction team led by two carpenters. It all starts at the factory, where the architectural drawings are turned into shop drawings that the computers can read. From here, the raw wood goes through a series of mills and routers, labeled, and finally packaged for shipping off to the site. Once the wood 9 pieces arrive at construction the site, the collection of milled beams and columns can be read and assembled like a puzzle. Mortises and together perfectly allows joints tenons to fit which be fully exposed and embraced in the architectural aesthetic of the building. Furthermore, this method preserves the age-old tradition of detailing and construction with wood for future generations to appreciate. ( www.archdaily.com ) The life cycle and forest management: In order to make timber to be a truly renewable material, a new lifecycle and forest management should The be trees developed. will be harvested to exploit their wood, and have to be Life cycle of timber replaced by growing new trees that will in turn, grow and absorb carbon dioxide. In order for this, it requires management of the forests in which timber grown. 10 Once a tree or forest has reached its limit it can be harvested, the carbon remains stored in any products produced whilst new tree can be planted allowing further carbon dioxide to be extracted. Europe has managed to reverse the issues of forest depletion and is actually increasing its forested area by approximately 650,000 hectares a year. This is thanks to successfully executed legislation that demands forest owners to replace harvested trees, as well as the Forest Stewardship Council [FSC] who promote the responsible management of forests internationally. Recycle and Reuse: Recycling and reuse capabilities are one factor that contributes to the great potential of timber to reduce the amount of construction waste going to landfill. Another benefit comes during the construction, using timber, as different from using concrete, results in no wet trades, and the associated waste, on site. It is also possible that all the timber used in a project can be pre-fabricated in the factory as mentioned before which means that there is possibly no timber waste production on site. Any waste created in the factory can be efficiently recycled or reused. Besides, timber used in construction has the potential to store large amounts of carbon, therefore the longer the timber is kept in use the greater the carbon stored in it. Therefore this requires any timber products to be reused and recycled wherever possible. For recycling and reuse of timber to be most effective this requires most consideration at the design stage, not just once a building is demolished. Using the specific module may do great help. We need to be aware that one day the building will become available as a material stock for potential reuse or recycling. There are three ways timber can be used after its initial use, that is material recycling, energy use [as biomass], and biological 11 decomposition. Another reason for carefully designing and detailing of timber for reuse is that: The demand for services and housing will change a lot depending on the changing circumstances and development of the society which requires buildings to be more flexible and temporary. We can draw a conclusion that, make timber component able to recycle and reuse is one of the most important aspect to develop sustainable timber buildings of low impact. Timber is Hunan Province: Timber has been used as the low impact building materials in many countries and many places, and there are many successful examples. While in China, where the timber was in the dominant position of building material for thousands of years, is it possible to reuse timber as the building materials in a new sustainable and eco-friendly way? Then I will take my hometown Hunan Province to discuss how to revival and develop this building materials. Overview: Traditional timber construction has been highly developed in China,but it has been replaced by some modern materials such as concrete and steel. With the sustainable requirements of buildings, timber should be reused and redeveloped in some area of China. The modern timber architectures has been developed successfully and been widely use in UK, Japan, Australia, etc. According to some survey, 47% of the new built house and 20.7% of the UK new built house were timber house. This evidence indicates that the traditional material can be revival after modern technology and construction which we can get some successful 12 experience from them, especially on the lifecycle of timber, forest management and prefabrication techniques of timber. Hunan Province located in the hilly area in the middle-south of China. Also this is an area of continental sub-tropical monsoon climate with four distinctive seasons and abundant in rainfall. The weather is humid especially in summer. One of the main tributary of Changjiang River flows across the region and there are numerous rivers and lakes in Hunan. The climate contributes to the growth of trees and the forest resource is abundant in Hunan: the forest coverage rate of Hunan has reached 57.1% these recent years. Many timber factories has been set up near the forest and woodland of Hunan Province, which endows this area the potential to develop new timber industries and timber construction. As belonging to the traditional Chinese timber construction system, Hunan has a long history of using timber as one of the local material as well. Besides, timber is not only used of building material in Hunan, but also can be used in different areas. For example, the timber furniture , the craftsmanship of the carving on the timber and the mortise and tenon of the joint has developed to extreme. Now the timber furniture is still very popular among local people. Some infrastructure are also made by timber as well, such as the timber bridge, and timber leisure facilities. Traditional timber buildings of Hunan: The timber buildings of Hunan started as the stilted style house, which looked like a bird’s nest that can protect the local people from the beast attack and the humid ground. Then after years of 13 experience, a unique local construction techniques and timber culture has been developed. The form of the timber buildings was developed because ancient Chinese focus a lot on the combination of the climate into architecture. Chinese believe that the nature and human beings is a integrated whole part, this idea was also reflected in the buildings and the organization of the garden and buildings. A series of theories about the climate and architecture has been developed to work as the guide of the architecture construction such as the location of the buildings, the directions of the buildings, etc. The most common form of the buildings in Hunan is the garden house. This form is developed according to the characteristic of the local climate. Since Hunan has abundant rainfall, in the typical garden house there will be a pool in the inner garden in the middle of the building. The gradient of the roof is quite deep than the house in north China, the slope of the roof is towards the inner garden, the rainwater will run into the pool rather than remain on the roof. It also do great help to the ventilation of the house, especially in cooling down the house in the hot summer. 14 Another interesting prototype of the timber house in Hunan was the . This prototype was developed from the original stilt style architecture. The formation of this hanging house is the combination the local climate and topography into the form of house. is because the humid weather of this area. To elevate the ground floor by stilt could protect the buildings from the humid and wet ground especially Hanging house of Tu-ethnic in spring. At the same time this form can also prevent some insect from destroy the building. The elevated structure can improve the ventilation as well. This special form of house has been developed in many areas of Hunan province especially at the riverside or in the hilly area. This type of house is totally eco-house that makes full use of the local nature resources, combine timber with local stone and brick. It shows some of the ancient sustainable and the willing to keep in harmony with nature of ancient Chinese. There is a traditional concept that to make full use of the material, from large panels to tiny piece of fragment. The ancient Chinese 15 has put great importance in stay in harmony with nature that we should learn a lot from that. Development Prospects of the Timber Buildings in Hunan: The modern urban development has ignored some of the local culture and local context. Overusing the modern construction and modern material has caused many problems not only in environmental aspects but also in the local context. In Hunan, the speed of development is so fast, many highrises and modern architecture made of steel, concrete and glass has been constructed in these decades. In order to make space for the modern architecture, many hills and valleys has been made flat, which made the local topography being totally destroyed. The micro-climate of the urban area has become not that confortable for people to live in. Also some air pollution and energy crisis made this situation much worse. By redevelop and reuse the timber buildings could be one of the way to solve these problems. For example, take full advantage of the special and unique prototype of the local hanging house could be a great way to protect the existing slopes. The local context could also be brought back by the revival of some of the traditional architectural language by using the timber. Combine the traditional construction techniques with the modern technology and materials to make it more stable and have a better seismic performance. At the same time overcome some of the weakness of the timber. Though it is not realistic to make all types of architecture by timber especially of some large-scale architecture. But it is possible to 16 start with some small-scale buildings such as timber residential buildings at the suburban area which is close to the forest and nature woodland. The prefabrication manufacture of the timber component can be introduced into this area, set up a module system for the timber manufacture could also be a way to recycle and reuse some of the timber component. Another important and helpful aspect is introducing the proper life cycle and forest management that has been mentioned before and develop a system of a recycling and reuse circulation of the timber materials. In this way, some of the existing problem about pollution and climate change might be relieved to some extent. Then with the development of the timber construction technology, the carbon can be stored into the fabric of buildings which is the sustainable and eco-friendly way. Conclusions: From the discussion above, we can draw a conclusion that the modern use of traditional material--timber as the building material is a sustainable and eco-friendly way to deal with some problems of climate change and energy crisis. By proper develop appropriate timber life cycle and the forest management and prefabrication of timber, it is possible to recycle and reuse of the timber products, and make it totally low impact and sustainable. This modern way can also be used in some area in my hometown. With the help of some of the existing successful experience, by combining the traditional form of timber house with the modern techniques could bring new life to the local buildings in Hunan Province. 17 References: Website: http://www.archdaily.com/158918/japanese-precut-timberconstruction/ http://oak.arch.utas.edu.au/tbia/article_srch_topic.asp?area=env&t opic=14 Fu, Phobe and Chapman, John. (2007) Timber Design Journal. Vol 12, Timber in Ancient China. Lin, Xiande. (2007) Green Architecture[M]. Beijing, Industrial Architecture Press. Zhao, Guangchao. (2006) Buzhi Zhongguo Mujianzhu, Shanghai, Shanghai Science and Technology Press. Shan, Deqi. (2004) From Traditional Residential House to Local Architecture, Beijing, Industrial Arhictecture Press. Huang, Jiajin and Qiu, Canhong. (2006) Hunnan Traditional Residential House, Changsha, Hunan University Press. Lu, Jiansong. (2008) Research on Timber Architecture in Hunan hilly Area, Changsha, Hunan University Press 18