Material Failures and Embodied Energy - Assignment Example

?Material Failures and Embodied Energy 518537) Introduction Conservation of energy is an important facet of building construction in recent times. Ways and methods of creating low cost and low energy buildings form an integral part of the new construction process. Low cost buildings by reducing the embodied energy of building materials are an important part of the new design process. (Lucuik Mark, 2007) The new building regulations have increased the stringency in using low carbon materials to safeguard the environment. Reducing the embodied energy in building materials form an important part of the new construction process. Source: Embodied energy in house construction, Energy Efficiency, 2006 Embodied Energy The Green Book brings out 18 recommendations on methods to reduce carbon emissions. This book forms an effective guideline in the designing of building using low cost materials. Embodied energy is the total energy that is required to construct buildings using materials like cement, aluminium and steel. However, this energy is not just the direct energy used but the total energy that would be required to source the material, transport it and ultimately use it in the construction. (Lucuik Mark, 2007) A few examples to further elaborate this point are as follows. Concrete blocks used in the construction industry involve not just the energy used in manufacturing the block but is the summation of the energy that would be involved in transporting it from the sourced location like China to its destination location like Saudi Arabia. It would also involve the additional energy that would be further required to process the bricks at the site to enable it in laying. Therefore any amount of energy that is used in the drilling and excavating machines to the energy that is used to sustain the people engaged in the excavation operations all sum up to form the total embodied energy of the product. (Lane Thomas, 2010) Source: Embodied environmental effects results comparisons: single family home, Lucuik mark, 2007 Source: Embodied environmental effects results comparisons: high rise, Lucuik mark, 2007 Measure of Embodied Carbon Sturgis Associates have brought a tool called RICS which gives a measure of the embodied carbon in different buildings. On an average it is said that a distribution warehouse has 60% embodied carbon, a supermarket which is always well lit up and uses lot of external energy during its operational time has an embodied carbon of 20%. A normal house has an embodied content of 30% which is somewhere between a warehouse and supermarket. The RICS further provides a certain degree of lifespan to each kind of building ranging from 20 to 75 years. (Lane Thomas, 2010) Therefore apart from the kind of construction, the total life span of the building structure all go into accounting the embodied carbon efficiency of materials. Measuring the carbon footprint of a building is a twofold process. It involves calculating the energy that is required in constructing the building and also adding the embodied energy of the materials that are replaced over a period of time during the building lifecycle. A number of tools apart from the RICS are available in the market that can predict exactly the embodied energy of the materials that are used in the design of the building structure. These give an idea about the embodied energy in construction and also the operational energy that would be used in the years to come. The problem however in using the different software’s that are available in the market are that each tool provides a different value of embodied carbon data. Hence the results that are obtained from different tools might differ. The other problem includes some industries like the Steel Industry providing blast furnace slag to the concrete industry. This enables them to claim that embodied energy of steel industry is lesser than concrete industry since they are actually conserving energy by utilising the energy used in the kilns to other industrial areas. However standardization of these embodied energy parameters are being laid down by the International Standards Organisation. (Lucuik Mark, 2007) Life Cycle Assessment Embodied energy is usually measured in units of mega Joules (mJ) or giga Joules (gJ) per unit weight (kg) or area (square metre) (Alstone Peter et al, 2011) This involves assessing the entire life cycle of a building product right from its inception stage to the time in which it is disposed off. This involves the energy that is summed up through all its intermediate stages through processing, transportation and construction. This is also called ‘cradle to grave’ and the method of analysing these steps in detail through each process is called Life Cycle Assessment (LCA) Source: Embodied energy in LED task lights, Alstone Peter et al, 2011 LCA assess the embodied energy of these building materials and also the operational energy that is contributed to the embodied energy in the form of extraction, water use and pollution caused during operation. The BRE ‘Green Guide to Construction’ contains the data base of all the major construction items used in the industry. A grading system is introduced ranging from A+ to E. A+ is considered a product having the best performance as far as compatibility with environment is considered. E is rated as having the worst performance. (HVAC applications, 1995) Embodied Energy Regulation Embodied carbon efficiency of different materials are being tabulated in the Green Book to regulate the carbon emissions target. Calculations could also be carried out to ascertain the embodied energy in building materials. These regulations could prevent developers from demolishing existing buildings and constructing a new one since this would increase the net carbon value of the buildings. The summation of carbon content is that of the building being demolished and the one that is coming up instead. Embodied Energy of common construction materials 1. Masonry Walls 2. Masonry Walls in terms of volume 3. Timber Products 4. Structural parts in terms of volume 5. Embodied energy of Insulation materials Building Sustainability and Different Construction Materials Sustainable Development forms the basis of conserving energy and reducing carbon content. It should satisfy the following criteria. (Joseph Paul & Tretsiakova Svetlana, 2010) 1. It should be energy efficient 2. The amount of waste generated should be minimal. 3. It should not pose health hazards. 4. It should not cause loss of precious water resources. 5. It should come at an affordable price. 6. Maintenance costs should also be less. 7. It should provide a radiant feel and generate a feeling of warmth to the occupants of the building. 8. Providing greater adjustability in terms of design and also one that provides greater space flexibility is an important parameter of sustainable building materials. Researchers have classified construction materials into six groups. These consist of concrete, wood, plastic, ceramic, stone and engineering metals. (Joseph Paul & Tretsiakova Svetlana, 2010) 1. Concrete and Cement- Concrete is the most widely used constructional material which is quite cheap and resistant to fire. The strength and flexibility of concrete can be improved using steel fibre reinforcements. However it is estimated that close to 7% of the CO2 emissions is generated by the cement industry. Concrete manufacturing also releases products like carbon monoxide and nitrogen oxides. (Cole R.J, 1999) The Cement Sustainability Initiative (CSI) is an initiative by the ten major cement companies to reduce the potential damages to environmental and also to human life during cement manufacturing. 2. Wood- Use of wood is always a matter of debate in construction industry. On one hand the argument is that use of wood cause lot of deforestation and reduces the forest cover over land. This in turn reduces production of oxygen. On the other hand, use of wood materials used in construction also reduces mans dependence on fossil fuels leading to energy conservation. ( Joseph Paul & Tretsiakova Svetlana, 2010) The following specifications are laid out for the use of timber in construction. (i) Use of low quality of wood for creating structures of simple design. Wood waste needs to be reduced and structures of robust design needs to be manufactured with the addition of minimum preservatives. (Levine S.B and Buchanan AH, 1999) (ii) Wood used should be certified. (iii) Recycled wood to be used wherever possible. (iv) The varnish or chemical used for providing surface finish to the wooden structures needs to be of low toxicity. Recycled fibreboard can be combined with coconut husk and also added with synthetic binders to be used in the manufacture of low cost flooring panels 3. Bricks and Stone- Bricks are usually made of materials like clay and shale which are considered to be in sync with nature. Solid wastes can also be utilized in brick production thus enhancing sustainability. (Energy Efficiency, 2006) Research has shown that energy input was found out to be in the range of 660MJ/ ton compared to fired bricks that utilize 4187 MJ/ton. Ceramics on the other hand consume 32240 MJ. (Joseph Paul & Tretsiakova Svetlana, 2010) 4. Glass and Plastics- Glass in windows provide for several important parameters of the operational energy of a building. Window spacing accounts for heat transfer and also forms an important facet of in house temperature on account of ventilation and the insulation that is provided. (HVAC applications, 1995) New Technologies like chromogenic technology have come up which change the colour of their surface on interaction with an electric field. Therefore on being exposed to ultraviolet rays these windows change in colour and can therefore control the amount of heat entering the building spaces. Further gasochromic windows have a layer of tungsten oxide covered with thin platinum. When exposed to hydrogen gas tungsten oxide reduces and the surface layer changes colour. On being exposed to dilute oxygen this process can be reversed. These windows are also referred to as ‘on’ and ‘off’ windows. (Joseph Paul & Tretsiakova Svetlana, 2010) The importance of plastics in building construction is that it provides increased resistance and low weight. Plastic products can be recycled however wastage of plastics can lead to degradation of the environment. Common plastics used are polystyrene, polyethylene and polyvinyl chloride. Source: Embodied energy, Sustainability 2010. Recent developments in the field of composite materials have found increased use in construction. These are also called self repairing composites. Pang and Bond have developed hollow fibre reinforced polymer composites that release dyes when there is a fracture of the composite fibre. It therefore provides method of locating cracks that may have occurred in the inner layers of the building materials. University of Illinois has developed a capsule containing a healing agent along with a catalyst that is in built into the composite material. When a crack is formed, the healing agent is released which combines with the catalyst and fills up the crack. The mechanical strength of such materials is considered very high along with good resistance to moist environments. (Joseph Paul & Tretsiakova Svetlana, 2010) Failure of Common Structural Materials Structural materials fail by the following methods 1. Aesthetic failure- The paint surface of buildings might experience flaking due o extreme weather conditions or on being exposed to torrential rain. 2. Functional failure- This involves leakage of roofs and walls on exposed to wet conditions. 3. Structural Failure- These include building parts experiencing failures in alignment due to different degrees of settlement that affect certain portion of the building. 4. Material Failure- Corrosion due to reactions with chemicals or formation of fungus due to moist conditions is the main reason for this failure. Metals degrading under severe conditions also cause material failure. 5. Non-structural Failure- Plaster peeling off surfaces and the polished planes of plywood coming off are examples of non-structural failure. 6. Reversible Failure- Failures on account of doors and windows that get stuck due to presence of foreign material or parts of the wooden frames undergoing expansion during summer months. 7. Irreversible Failure- Incorrectly designed columns tend to experience buckling on account of excessive column heights and also on interactions with chemical atmosphere or acid rain. Methods to prevent failures 1. The new methods to prevent failures involve using sustainable construction materials that are energy efficient and pose no health hazards to the environment. The most recent advances include using various types of reinforcements in the form of bamboo fibres and agricultural wastes in the strengthening of constructional materials. This reduces the brittle nature of concrete to a large extent. Apart from preventing structural failure it also reduces net weight of the structure. Bamboo is also finding increased uses in the laying of floors and fibre boards. Earth that is compacted earth along with straw and bamboo posses’ high compressive strength and have been finding increased uses in the construction industry. Materials that are produced as a mix of several ingredients tend to posses increased resistance to acid rains and chemical attacks. Use of High performance concrete (HPC) which have low water to cement ratio is another development. These use super-plasticizers which enhance the compressive strength to 40-50 MPa and its low porosity makes it capable of withstanding low temperatures and chemical attacks. (Joseph Paul & Tretsiakova Svetlana, 2010) New products like SCC or self compacting concrete are being used to reduce the embodied energy at the same time reducing cost. These can take any form and therefore energy required for vibration is minimal. Complicated shapes can also be designed using SCC. Source: Embodied Energy Comparisons, Lucuik Mark, 2007 Production of compact reinforced composite (CRC) and Ductal CRC which are fibre reinforced has lead to further increasing the compressive strength of concrete to 150-400 MPa. Considering the embodied energy aspect Ductal technology uses 65% raw goods and 51% of energy. (Ductal Concrete, 2010) Compared to regular concrete the CO2 emission is only 47%. Use of nanotechnology by strengthening concrete with nano fibres is the latest technology that increases the compressive strength of concrete multi fold and also cleans the surface of buildings automatically. TiO2 molecules present in this mix release an electric charge on exposure to sunlight. These oxidize the organic or non-organic wastes that are formed on wall surfaces which are then cleansed away by rain. TiO2 present in this concrete can also remove harmful gases like nitrogen oxide. Nanosensors that are incorporated in these building structures have the added advantage of getting a database of stress levels, pH levels, temperature, moisture and corrosion that is taking place over time. (Nanotechnology for Green Building, 2007) This helps in the designer plan his buildings accordingly for that particular area of location and for similar type of loadings that are envisaged. Conclusion New developments have been taking place to assess the net carbon content of buildings. UK has made rapid progress in carbon content profiling using the RICS tool. It has found that 42% of emissions of the new rise buildings have been of embodied form while 58% of the carbon content is of operational form. (Cole R.J, 1999) Developments are in progress to reuse the existing building materials on demolition of a structure so that the net embodied energy content is kept at a minimal. However such a development would make the contractors an unhappy lot since use of new construction materials would be restricted resulting in lower profits to these contractors. The clients on the other hand would be a happy since they would be able to construct the building of their choice using reduced carbon content and lower costs. Reference List 1. Lucuik Mark, 2007, Estimating the Environmental Consequences of Building Envelope Failures, ASHRAE 2. HVAC applications, 1995, ASHRAE Handbook, American Society of Heating, Refrigerating and Air-Conditioning Engineers. 3. Energy Efficiency, 2006, Foxcliffe Farm Ecovillage, Person & Hulme Developments. 4. Alstone Peter et al, 2011, Embodied Energy and Off-Grid Lighting, The Lumina Project Technical Report 9. 5. Joseph Paul & Tretsiakova Svetlana, 2010, Sustainable Non-Metallic Building Materials, Sustainability Journal ISSN-2071-1050 6. Ductal Concrete, 2010,Available at http://www.ductal-lafarge.com/wps/portal/Ductal, [accessed on 7th Aprul, 2011] 7. Nanotechnology for Green Building, 2007, Green Technology forum, available at http://www.greentechforum.net, [accessed on 7th April 2011] 8. Levine S.B and Buchanan AH, 1999, Wood based building materials and atmospheric carbon emissions, Environmental Science Policy. 9. Cole R.J, 1999, Energy and greenhouse gas emissions associated with the construction of alternative structural systems, Building Environment. 10. Lane Thomas, 2010, Embodied energy: The next big carbon challenge, available at http://www.building.co.uk/technical/embodied-energy-your-next-crisis-is-on-its-way, [accessed on 8th April 2011] Read More