Design Evaluation: The Performance of the Earth Materials - Essay Example

Constructability is one of the many performance attributes that must be considered during the design process for a building or other constructed facility. Constructability must be analyzed along with all other attributes such as: Structural strength and stability, Level of complexity of structural assembly, Cost of labor, materials and equipment, Lighting performance, Acoustic performance, Maintainability, Durability, Ease of facility operation and others. Design evaluation is a dynamic process. However, constructability analysis should be performed at least at two important stages. Globally it is estimated that a third of the worlds population live in houses of earth construction. These are both modern and traditional and occur in most cultures and climates. In the U.K. there are estimated to be 500,000 inhabited earth buildings. Earth was the principal material used in U.K construction until the 18th century and Scotland retains a rich heritage of earth construction with much regional variety. Many surviving buildings are not recognised as being of earth construction and much work has been done on this in recent years by Historic U.K and others.( CIRIA Special Publication 116, Environmental Impact of Materials, vol A, 199) In the United Kingdom today copper is a popular material used for facades, roofs and other external building elements on some of the most exciting modern designs. But this has not always been so. Historically, copper roofs several hun­dred years old can be seen on many British city skylines, although usually limited to churches, civic buildings and other important structures. During the twentieth century, copper roofs became more widely used for ordinary buildings – although many were of little architec­tural quality. Unfortunately, poor de­tailed design and installation techniques resulted in technical failures and the material fell out of fashion until the 1980s. Then, the copper industry intro­duced modern installation techniques to the UK – including the long-strip meth­od – and launched a promotional cam­paign to make architects aware of cop­per as a thoroughly modern architectural material. This ‘Copper in Architecture’ campaign continues today.(Article by Tom Woolley in Sustain magazine, vol 3 no 3) It highlights the ability for copper sheets to be easily formed to suit any three-dimensional shape, making it a suitable weatherproof covering for virtually any external surface including roofs of all pitches, vertical cladding, gutters, soffits and even sculptural elements. Architects now recognise that it is one of the few materials that can offer complete mate­rial continuity and real freedom of form in architectural design. Copper’s natural development of a patina, with colours changing from bright copper to chocolate brown and eventually to the distinctive blue-green, is one of the unique characteristics making it popular with British architects. This patina can take years to develop and in some circumstances may never appear at all – for example on vertical surfaces. So, one of the most popular recent innovations has been the devel­opment of patination treatments to provide a green, textured surface straightaway, similar to the natural patina which gradually develops in the open. Pre-oxidised copper sheets are also available with a darker colour than the bright, mill-finished copper - con­cealing hand marks or other blemishes that can affect bright copper for a short time after installation. Apart from its inspirational design potential, British architects are also Collective professional bodies were first organised in Britain in the 19th century in response to an increasingly complex, industrialising world. These bodies began to establish a codified corpus of knowledge and methods of practice for each discipline. In architecture it also involved an assumption of the role of protecting the building client and the title and status of architect. These processes became enshrined in statute in the 1930s. The education of architects at the time was ad hoc, and largely took the form of office based tutelage. Concurrently, British architectural education was growing within the existing forms of higher education. The past 40 years have seen it become firmly embedded in the university structure, helping to make explicit the distinction between architectural education and architectural practice. It is for this reason that this document sets out a benchmark standard for undergraduate architecture courses whether they are professionally recognised or not (XCO2 Conisbee, Insulation for Sustainability: A Guide for BING, XCO2, 2000.) The Building Act and Building Regulations deal with detailed issues on an individual building level. They aim to ensure the health and safety of people in and around buildings and deal with issues such as conservation of fuel and power, ventilation, fire safety and access for all. The planning system in England is designed to help ensure that suitable land is available for development in ways that accord with environmental, social, and economic policies, and that such development is consistent with the principles of sustainable development. Unlike the building regulations, which are prescribed centrally, the planning system has the opportunity to take a holistic view in ways sensitive to local circumstances and concerns. There are currently a few designers with expertise in this field. Easier access to information and technical support in the U.K., as well as an accepted standard, would facilitate design opportunities( Building for a Future magazine, vol 11, no 4) . There is currently no accepted standard for earth construction within the U.K. This lack of control documents is a significant restraint on the development of earth construction. A small amount of testing and research in earth construction has been carried out in the U.K., mainly focussing on traditional practices. This field of research is growing in Europe and is necessary to demonstrate the credibility of new earth building. There are potential testing facilities in Scotland for earth building materials but a lack of expertise to carry out this work. In the U.K. training and education initiatives in earth construction exist on a small scale attached to specific projects or as part of wider university or college courses. German experience illustrates the potential for official recognition with industry-based qualifications in earth building. Wider acceptance of earth building technologies has also been promoted through regional interest groups and specialist publications as well as coverage in the generalmedia. Earth can be used in a wide variety of ways within construction to form walls (both load bearing and non-load bearing), floors, roofs and other elements. It can provide good thermal and acoustic insulation and has a particularly good ability to regulate internal air humidity and quality. If properly used, it is a durable and beautiful material. The most common techniques of earth construction are: Mudwall. This is a simple historical technique of monolithic walling, using an earth straw mix. Rammed Earth. In this technique earth is compressed between temporary shuttering to create dense monolithic walls. Earth Brick. This is an ancient material comprising un-fired bricks of varied composition. Compressed Earth Block. This is a modern material similar to earth brick, but having better load bearing capacity. Earth Infill in Timber Frame Construction. This involves light earth/fibre mixes either formed on site or in block form. It can give good thermal insulation and is particularly appropriate to Scottish construction practices. Earth Products. A range of prefabricated products is available, including blocks, boards and panels. These are currently imported from Germany. Earth Plasters. These are effective as either traditional wet plaster or as plasterboard There are numerous tools and assessment methods available for designing and building more sustainable and the choice is often confusing. A traditional objection to increasing the role of planning in promoting sustainable development is that it is a profession concerned solely with land use issues, and that building techniques, choice and source of materials are best dealt with by Building Regulations. However, as Part One explains, Building Regulations are prescribed centrally, are more narrowly focused, and have a role in ensuring minimum standards. Planning, on the other hand, has the opportunity to take a holistic view in ways sensitive to local circumstances and concerns. Planners need to be able to consider the full range of sustainability issues. The main justification for involving the planning system in determining anything more than issues of land use and location is the need to advance quality design, in environmental and social terms. However, identifying sustainability issues that can legitimately be covered in development plan policy is still a contentious issue and has led in some cases to conflicts with, and formal objections from, regional planners and the Secretary of State. In addition, the resources needed for achieving good quality design are substantial. Therefore, from practitioner.s point of view, there is need for a clearer national planning framework. (Becky Little and Tom Morton, Building with Earth in Scotland: Innovative Design andSustainability, Scottish Executive Central Research Unit, 2001) There are many lessons to be learnt from traditional earth building practice which could inform a modern vernacular for earth building: The longevity of earth buildings is due not only to the materials and techniques employed, but also to the quality of workmanship and appropriateness of the design to a particular setting and region. The durability of earth buildings is also determined by appropriate maintenance and repairs that are compatible with the original construction. In the past earth building was generally a seasonal occupation reliant on good weather conditions. Prefabrication of dry earth components, such as blocks, and protected working environments could widen the scope for year-round use of these materials. Traditional earth building techniques, which are simple and labour intensive, could be adapted to modern self-build forms of construction. With developments in mechanisation these techniques could also have relevance for modern industrial applications. Surviving earth structures in Scotland illustrate the appropriate use of local materials, which has resulted in diverse and distinct cultural patterns. The maintenance of this cultural diversity and local knowledge is central to the debate on sustainability. Earth used in building has good strength in compression, but less strength in tension, especially in its damp state. When earth is used as a load bearing material, forces must pass down within the thickness of the structure to the ground. For this reason monolithic loadbearing walls tend to be thick (450-900mm)( Anink, Boonstra & Mak, Handbook of Sustainable Building, James & James, 1996). However, it is possible to construct slender walls, arches and vaults in earth if care is taken to support these structures while they are drying out. The compressive strength of earth can be increased by compaction, which raises the density of the material. The lasting qualities of soil as a construction material are apparent in the traditional buildings that have survived over two centuries of use. Earth buildings in cold damp climates need to be protected from prolonged contact with water. This can be done by placing the earth walls on a water-resistant plinth out of reach of groundwater and splashing; by protecting the walls from rain with an overhanging roof; and by protecting exposed surfaces with breathable surface coatings or cladding. Impermeable membranes such as cement floors and renders should be avoided as they can trap water within the walls and encourage rising damp. Earth surfaces are sensitive to abrasion. Durability can be improved by compaction, application of surface coatings or by changing the earth mix. Additives and stabilisers are also used to improve wearing qualities. The longevity of earth buildings is due, in part, to the regular maintenance regimes that were integral to traditional practice A change of attitude is necessary if modern earth buildings are to survive equally well as current construction practice promotes ‘maintenance free’ products such as cement renders and masonry paints. These are incompatible with earth backgrounds. (You Build’, magazine of the Walter Segal Self Build Trust, no 14) It could be that the actual design of build­ings is at fault. In fact many people think that we may have something to learn from ancient systems of architecture, because they clearly addressed fundamental design issues such as layout, proportion and even orientation of buildings. Every building, it is said, must have right orientation and correct proportions and measurement. The various activities to be undertaken in the building must be placed in the appropriate part of the structure; and the site should be clearly defined by a boundary fence. When all the ingredients are right, the finished effect is said to have proper vastu, a sanskrit term which refers to the overall qualities of the site. It is with these prescriptions for proper vastu that the system extends the usual concepts of natural building. The theory is that we are all a part of nature in its widest sense and so need to construct buildings which take into account the full range of environmental influences. The most powerful influence - as detailed in the feature on solar energy two issues ago - is from the sun. Rammed earth technique is the suitable and safe in this modern era and also the demand of the famous architects.It is important to temper enthu­siasm for the advantages of using a particular material, with an aware­ness of its limitations. Architects recognise that exposing an unprotected earth wall to the weather, especially in our wet Welsh climate, is unlikely to be successful and have therefore elimi­nated that risk. Architects also realise that an external earth wall in itself is not going to achieve the high levels of insulation which we regard as desir­able. The building, therefore, is designed with load bearing rammed earth wall panels and columns, located within the footprint of the building and surrounded by a super ­insulated, timber stud, external wall. With the earth components protected from the elements, we have then concentrated on demon­strating the earth’s structural, load bearing capacity, of which we are confident. We have also incorporated issues of ‘build ability’ into our design. It is important with rammed earth construction that the materials be kept as dry as possible. We therefore needed a sheltered area in which to install it, and a post and beam timber frame was used, so that the roof could be constructed, temporarily propped and made weatherproof, before ramming commenced. Similarly, access had to be given at the top of the wall panels and columns, for the builders to ram the top section. This would not have been possible if the panels and columns had been located at the eaves and so they were positioned in the centre of each truss, under the kingpost. A special shuttering system was devised for the wall panels, which were designed to suit the length of a standard sheet of plywood, with 150 mm gaps in between each panel to accommodate the cramps which held the shuttering together. The Architects also tried very hard to avoid the ‘mud hut’ image of earth construction. Our rammed earth columns and wall panels have crisp straight profiles and smooth polished surfaces, which, paradoxically, seem to enhance the modernity and tall well-lit spaces associated with contemporary commercial buildings. The process of preparing the earth mix for ramming or block-making was quite labour intensive. It was found necessary to pass the earth through a screen again, to break up compacted areas and remove the few remaining items of large aggregate. Careful batching was necessary to ensure the correct proportion of clay and where neces­sary, lime was added. These components were mixed dry in a large drum mixer and water was then sprayed on cautiously and spar­ingly until the mix was moist but still crumbly. A certain amount of trial and error went into getting the moisture content just right, but even­tually the builders knew how many sprays were required for a given quantity of soil. The shuttering was struck as soon as the ramming was finished. The results were generally very pleasing, although there were occasional areas of ‘pull-off’ where earth had adhered to the shuttering. In some instances, surface cracks appeared which were The rammed earth elements have taken an enormous amount of time and effort, both pre-contract and during construction, to bring to fruition. We consider this to have been worthwhile, partly because of their stunning finished appearance and their major contribution to the aesthetics of the building. In addition, CAT is in the business of testing and demonstrating new tech­nologies which will hopefully inspire others to further innovations. Compressed earth blocks may however, offer a simpler route to introducing earth construction into mainstream building practice. Given that the form and function of an earth block are similar to those of a concrete block, the construction method is conventional, and quality control is relatively straightforward, there may well be a greater take-up of this particular earth-based tech­nology. �Correct proportion is regarded as equally important. Proper proportion is a feature of everything in nature, including our own bodies - the heart is always in the same place and proportion in relation to the mouth, eyes, legs. Likewise, MSV prescribes extremely precise proportions for a house - it says there is literally an ideal proportion for every room, which relates to the rest of the struc­ture and to the proportions of the people who live there Bernard McKeon, a town planner and civil engineer from Galway, built a 2500ft2 MSV home three years ago, having seen various examples in the United States. “It’s an extremely similar process to building a regular house,” he says, “the main difference being the consultation process at the begin­ning, where we sent our drawings off to the international Maharishi Sthapatya Veda consultation service (nowadays based in North Carolina), and received feedback on correct proportions and so on.” The results, he reports, are “a million times worthwhile. “ He, and his wife and children are delighted with their new home. “If there’s one element that’s really strong, it’s the feeling that you’re protected here, that there’s nothing you can’t accomplish. It’s the most extraor­dinary experience of my life, it’s hard to imagine that a physical structure has that kind of influence. (Environmental Building News, vol 11, no 9) CONCLUSION The performance of the earth materials was assessed in the following respects: a) Design: how the earth materials were designed to work with other materials and within the whole building, the use of technical data, compliance with regulations, predictability of performance. b) Buildability: ease of construction, adaptability to standard labour skills, site storage, waste management, health & safety issues, robustness through construction. c) Durability: shrinkage, damage from abrasion & impacts. d) Thermal Performance: field monitoring of energy used in space heating and of steady state heat flows in the occupied house over one year. e) Moisture Performance: field monitoring of relative humidity in a number of key locations in the occupied house over one year. The durability and versatility of this type of earth construction is demonstrated by traditional Scottish earth buildings. Earth materials have significant environmental advantages when compared to many other building materials. In particular they have significant potential to reduce greenhouse gas emissions and waste generation within the sector. There are a diverse range of earth materials and construction methods which can fill a variety of roles within a building. Applications as light infill for timber frame construction and as earth bricks in internal partitions have perhaps the most immediate potential in the uk context. There are no technical reasons why earth materials should not be used in contemporary Scottish construction. There is sufficient professional expertise within the uk construction industry to successfully use earth materials, though the knowledge and skills base is very small. There is, however, a considerable body of expertise within Europe, and international links have been established by Scottish practitioners. There are no earth materials currently being mass produced in Scotland. Some are being imported from Europe and the existing Scottish manufacturing infrastructure could be readily adapted to produce these materials. The lack of accepted standards is a significant restraint on increased use of earth materials. There is a significant role for training and education in the wider acceptance of earth construction techniques in UK. At present this involves a small range of initiatives focussed within university education and specialist training events. References [2] CIRIA Special Publication 116, Environmental Impact of Materials, vol A, 1995 [3] Eco Tech magazine, November 2000 [4] ‘You Build’, magazine of the Walter Segal Self Build Trust, no 14 [5] Hastoe Housing Association, Timber Frame Housing, London, Sustainable Homes [6] TRADA Technology Ltd, Sustainable Timber, Sustainable Homes, High Wycombe, [7] Environmental Building News, vol 6, no 3 [8] Bjorn Berge, Ecology of Building Materials, Butterworth Heinemann, 2000 [9] TRADA Technology Ltd, British Grown Hardwoods, High Wycombe, 1996 [10] XCO2 Conisbee, Insulation for Sustainability: A Guide for BING, XCO2, 2000 [11] Building for a Future magazine, vol 11, no 4 [13] Building for a Future magazine, vol 12, no 2 [ [15] Borer, P. & Harris, C. The Whole House Book, Machynlleth, Centre for Alternative Technology Publications, 1998 [ [17] Lime Technology Ltd. website, accessed 04/11/04, www.limetechnology.co.uk [18] From MSc thesis by Sean Quinn, University of East London. [19] Anink, Boonstra & Mak, Handbook of Sustainable Building, James & James, 1996 [20] Becky Little and Tom Morton, Building with Earth in Scotland: Innovative Design and Sustainability, Scottish Executive Central Research Unit, 2001 [21] David Olivier and John Willoughby, Review of ultra-low-energy homes – 10 UK Profiles, BRECSU, 1996. [22] Hockerton Housing Project Launch Brochure [23] Barbara Jones, Building with Straw Bales, Green Books, 2002 [24] Environmental Building News, vol 11, no 9 [26] Article by Tom Woolley in Sustain magazine, vol 3 no 3 [27] Gernot Minke, Earth Construction Handbook, WIT Press, 2000 [28] Personal communication with Dr Peter Bonfield, BRE Read More