Embodied Energy in House Construction - Essay Example

?Material Failures and Embodied Energy 524202) Introduction In these times of energy recession it is very important to carry out conservation energy with the consumption of minimal energy. Research activities are being carried out to devise innovative methods of creating low cost and low energy buildings. In this aspect the the primary aim to reduce the embodied energy of building materials so that the total energy consumed right from its inception stage to its completion is kept at an optimum. (Lucuik Mark, 2007) New building regulations restrict the carbon content of materials used in the construction process and therefore indirectly reduce the embodied energy that would form part of the building materials in the new construction process.. Source: Embodied energy in house construction, Energy Efficiency, 2006 Embodied Energy There are 18 criteria laid out in the Green Book that form the basis of ways to reduce carbon emissions. This book serves an effective control in helping construction companies identify the materials that have a high percentage of embodied energy contained in them. This helps in constructing the buildings with low carbon content hence lower embodied energy. Embodied energy can be defined as the total amount of energy that is required to construct buildings using materials like cement, aluminium and steel. Total energy that is defined in this context means the sum total of all energy that would be required to build the material, transport it to the site and also the energy that would be used in construction purpose. (Lucuik Mark, 2007) To elaborate further a company engaged in construction activities in Kuwait might source these construction bricks from China. Therefore the embodied energy of this brick would include the energy used in brick construction in China, transportation energy from China to Kuwait and ultimately the energy used to lay the brick and constructing it in Kuwait. It would also involve the additional energy that would be further required to process the bricks at the site to enable it in laying. Thus all the energy that is used in machines engaged in excavation and shoring out raw materials, to the energy that is required by the human personnel in construction of the building at site go into the summation of energy of the product which is defined as its embodied energy. (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 There are a number of tools that are available in the market which enables one to assess the percentage of embodied carbon in different buildings. Sturgis Associates use a tool lnown as RICS to gauge the embodied carbon of different types of buildings engaged in operations of different nature like store house, work shop facility and supermarkets. The embodied carbon content of a storage warehouse exists in the range of 60% while a supermarket which is always lit up with snazzy lights to attract customers has an embodied carbon of 20%. A normal household is a mix of these two types of buildings and has an embodied carbon content of 30%. Another factor that defines the calculations used in RICS includes the life cycle or the total life of the building. These may vary from 25 to 80 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. Apart from the RICS there are a number of software’s available in the market capable of predicting the embodied energy of the construction materials used in buildings. Apart from this energy the operating energy that would also go into the daily functioning of the building over its entire life cycle would also be an output that are provided by these softwares. However the main concern is that none of this softwares are standardized in the sense that output values obtained from each of the softwares vary and thus an accurate calculation can never be made. However the objective of approximately estimating the embodied carbon of different buildings is attained. There are some industries like the Steel Industry which as a result of its chemical processes generate a lot of slag. This slag is passed onto the concrete industry which can be effectively used in cement production. Thus the actual energy that is consumed by the Steel Industry is less as a saving is made in the form of slag. Thus these industries can claim to have lower embodied energy. These are however being standardized by the International Standards Organisation and one should be able to accurately gauge embodied carbon in the construction materials without much of a variation. (Lucuik Mark, 2007) Life Cycle Assessment The units that are used to measure Embodied energy include mega Joules (mJ) or giga Joules (gJ) per unit weight (kg) or area (square metre) (Alstone Peter et al, 2011) Life Cycle Assessment is also referred to as the ‘cradle to grave’ process since the the total energy that is required for a construction material right from its inception stage, procurement and ultimately to its use in the actual construction process is summed up. The energy that would also be consumed during its operating stage till the material or structure is disposed off also add up to its embodied energy. Therefore the process of assimilating all these energy cycles through each stage 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 of raw materials, water consumed in the extraction and other related processes and atmospheric pollution caused during operation. All the major construction items that are likely to be used in buildings have been listed in the ‘Green Guide to Construction’. This facilitates the fabricator in selecting materials judiciously as the materials have been graded from A+ to E. A material with a grade of A+ considered as a product with superior performance while E has the worst performance. (HVAC applications, 1995) Embodied Energy Regulation New Regulations listed in the Green Book tabulates certain guidelines to help builders ascertain the Embodied carbon efficiency of different materials. There are tables and calculations to find the embodied energy in building materials. Developers who care about the environment would in such cases be disinclined to demolish old buildings and construct new ones instead since this would increase the net carbon value of the buildings. This is because the carbon content would be the sum total of the old building and the new one that is taking its place. 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. The building materials should not be high on energy consumption. 2. Waste generation should be reduced. 3. It should be eco friendly and be in sync with the environment. 4. Water usage in construction should be optimum. 5. The prices should be attractive. 6. Maintenance should not be cumbersome. 7. The occupants in the house should feel at home and the materials should radiate positive energy. 8. The use of these materials should provide greater flexibility both in design and construction. 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 commonly used construction material since it is cheap and can be procured easily. Adding steel reinforcement can reduce the brittle nature of the concrete and make it flexible to a certain extent. There are however negative traits associated with this industry as it accounts for 7% of CO2 emissions. These by products of construction include carbon monoxide and nitrogen oxides. (Cole R.J, 1999) The Cement Sustainability Initiative (CSI) is a recommendation laid out by the leading players of the cement industry on ways to reduce environmental damage and minimise health risks to humans. Source: Embodied energy, Sustainability 2010. Concrete is considered to be of highly brittle nature and therefore finds itself cut off from the construction of several equipments like storage tanks and pressure vessels. This is because concrete has the capability of taking compressive load. However, it fails by sustained tensile load. To provide a bit of ductility to the concrete steel reinforcements are put in place to allow for an expansion without failure. Yield strengths of steel being quite high, provides the concrete to take both tensile and compressive loads. (Yakut Ahmet, n.d) 2. Wood- Wood can be used in construction industry as this is the best material that is compatible with the human body. A good finish is also aesthetically more superior to concrete. However the damage to environment and to forests in particular is a deterrent to extensive use of wood. Oxygen generation is depleted on one hand but on the other mans dependence on fossil fuels is reduced. ( 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 by adding preservative that are not harmful for humans. (Levine S.B and Buchanan AH, 1999) (ii) Certified wood should be used and recycling of wood wherever possible should be encouraged. Coconut husk combined with fibreboard can be used in the production of flooring panels. 3. Bricks and Stone- Clay and shale are the main ingredients that go into making bricks and stone. These are environment friendly and are sustainable ecologically. (Energy Efficiency, 2006) Un-fired bricks generated energy in the range of 660MJ/ ton compared to fired bricks that utilize 4187 MJ/ton. Ceramics however consume 32240 MJ. (Joseph Paul & Tretsiakova Svetlana, 2010) Buildings constructed of stone usually suffer damage due to seismic loads on account of earthquakes having a intensity of MSK VII. This failure occurs mainly at the ends and at T junctions. The surfaces stones are also of pyramidal shape and hence do not have proper contact to increase bond strength. Damage to these structures can be avoided by limiting the height of buildings to 2.5m and wall thickness to a maximum of 450mm. Unsupported wall length to be kept a maximum of 7m. (IAEE manual, n.d) 4. Glass and Plastics- Judicious use of glass panes in building define the HVAC requirements of the building and ultimately its embodied energy since this controls the amount of sun rays that would be entering the rooms of the work space or living area. (HVAC applications, 1995) Similarly, there are chances that glass might break due to its highly brittle nature. Lateral cracking was observed in glass panes on contact with wind speed above a certain limit. For thin panes glasses cracks originate in the form of a star while thicker plates failure propagates in the form of cone cracking. (Grant P V and Cantwell W J, 1999) Source: Energy Efficiency, 2006 Chromogenic technology which is a new technology changes colour on being exposed to UV rays and therefore are able to control the amount of heat entering a building area at different points in time. Gasochromic windows have platinum coated tungsten oxide layers which when exposed to hydrogen change colour preventing sun rays from entering the work space. The process is reversed on being exposed to oxygen.(Joseph Paul & Tretsiakova Svetlana, 2010) Plastics like polyethylene can be easily be recycled and offer increased strength characteristics at cheaper rates. Source: Lucuik Mark, 2007. There have been many technical advances in the use of construction materials. Pang and Bond have designed hollow fibre reinforced polymer composites that on being exposed to excessive loads release dyes indicating the presence and location of a crack if formed. Certain chemicals along with catalyst are contained in capsules that act swiftly to repair minor cracks that may generate in the inside of the material. The capsule fills up the cracked space and prevents discontinuities from seeking in. The material is of high strength and resistant to wet environments. (Joseph Paul & Tretsiakova Svetlana, 2010) Failure of Common Structural Materials Structural materials fail by the following methods 1. Functional failure- Roofs and walls may develop leaks when exposed to wet conditions. 2. Material Failure- Formation of fungus and other corrosive growth that may cause material deterioration can also cause material failure. 3. Irreversible Failure- Excessive buckling loads due to long columns without sufficient bracing and supports may cause material failure. 4. Aesthetic failure- The paint may peel off from building surfaces due to extreme weather conditions. 5. Structural Failure- Differential settlement due to insufficient compaction or due to natural earth movements may cause certain portions of the building to develop cracks. 6. Non-structural Failure- Polished surfaces losing its sheen and top surfaces from mica boards coming off are examples of non-structural failure. 7. Reversible Failure- Insufficient gaps to account for minor thermal expansion of wood joints may get the windows and door parts to remain stuck during summer months. Methods to prevent failures 1. Reinforcements of different varieties are now being combined with concrete to reduce the brittle nature of concrete and using it in absorbing a certain degree of combined loads. Bamboo, jute and flax are some of the materials that are being combined with the traditional constructional materials. Reduction in weight also reduces the weight of other structural members. Bricks are being constructed using clayey earth that is being compacted along with bamboo fibres. These posses enhanced compressive strength and are also resistant to acid rains and other 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) Self compacting concrete is also used in the new generation construction materials since the energy required for vibration is less and irregular shapes can be constructed. The embodied energy of these bricks is also less. Compact Reinforced concrete and Ductal Compact Reinforced Concrete have increased the compressive strengths of concrete to 150-400 MPa. The CO2 emission is at 47% which is lower than the traditional concrete manufacturing. (Ductal Concrete, 2010) Nanotechnology is also being widely used in increasing the compressive strength of building materials. Source: Embodied Energy Comparisons, Lucuik Mark, 2007 The TiO2 molecules oxidize the organic and non-organic accumulation on the wall surface and wash it away with the rain thus maintaining the aesthetic beauty of the wall surfaces. These nano-sensors also act as a database accumulator of the kinds of loads, stresses, temperatures, pressures and moisture the building is subjected to and help in redefining design parameters. This also helps in optimum design leading to cost saving. (Nanotechnology for Green Building, 2007) The advantage is that conservative designs that arte bulky, expensive and also labour intensive is reduced to a large extent. Source: Energy Efficiency, 2006 Present Standards The standard for Life Cycle Assessment is set up by the International Standards Organisation. In 1993 a code named “A code of practice was put forth in 1993 by the Society of Environmental Toxicology and Chemistry. (SETAC) The interpretations of this document were later incorporated and brought out as ISO 140140 and ISO 14044. (M K Dixit et al, n.d) Conclusion In this new age when developments are taking place to bring out new construction techniques that are eco friendly, the assessment of embodied energy in the construction materials go a long way in reducing carbon emissions. Different softwares available in the market provide inputs and calculate the embodied energy of materials sourced from different locations. In the operational aspect the traditional lights are being replaced with energy efficient bulbs that reduce the embodied energy of the building during its operational life cycle. (Cole R.J, 1999) Efforts are on to keep the environmental pollution minimal while at the same time not compromising on infrastructure building that needs to keep pace with the developmental activities. 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] 11. Typical Damage and failure of stone buildings IAEE, n.d, Stone Buildings, available at http://www.nicee.org. , accessed on 8th May 2011] 12. Yakut Ahmet, n.d, Reinforced Concrete Frame Constuction, Middle East Technical University. Turkey. 13. Grant P V and Cantwell W J, 1999, Impact Failure modes in glass structures, 14. M K dixit et al, n.d, Protocol for Embodied Energy Measurements Parameters, Life Cycle Assessment. Read More