Modern Energy-Efficient and Sustainable Housing - Report Example

Modern energy efficient and sustainable housing Suitability of the materials for various components with respect to mechanical properties Sustainable building materials is basically defined as materials which can be produced and sourced locally, thus reducing transportation costs and carbon dioxide emissions. These include recycled materials that have low impact on the environment, need lower energy compared to conventional materials, are thermally efficient, financially viable, and have lower toxic emissions. When selecting the construction materials different properties such as mechanical properties like tensile strength, hardness, impact strength, chemical properties, and resistance to the environmental degradation are considered as they dictate the method of production, the cost and the service life (Chiras, 2004). The material selection and design of components requires the consideration of process requirement, the availability of the material, the operation and the alternative materials vis-a-vis the durability and the cost. Some materials are selected because of their strength, while others are preferred because of the cost or aesthetic value. For example, bricks are selected for walls because they are locally available and thus the cost of transportation and carbon emissions are reduced. Although it requires labour to prepare, bricks have good insulation properties and are light in weight making them easy to handle. They are also inert and cannot react with the environment (Calkins, 2009). Due to the large surface of the roof, and its exposure to rain, the selection of roofing material will affect the overall energy efficiency of the construction. Concrete tiles roofing provide good insulation properties and have significant energy efficiency on the structure. Although this kind of roofing is expensive because they are labour intensive and the materials used to produce it are expensive, the long roof life reduces the material wastes, the operating cost and saves energy. The weight of the concrete tiles requires reinforced roof structure and skilled labour, but it last longer and has aesthetic value (Mehta et al., 2013). Wood frame is selected because of the cost of production and less emissions. Lumber recovered after demolition can be used for renovations, new construction, and for aesthetic and environmental reasons. Timber framed structures can be made from recycled wood because large logs may not be found easily. The timber frame is recyclable, nontoxic and has good quality compared to some available lumber. Concrete are also used on the floor because of their strength and durability. The cement used to produce the concrete for the floor and the roof tiles consumes a great deal of energy in their manufacturing process. However, concrete produce a long lasting floor and tiles which have good thermal mass insulation properties. They are also resistant to stains, non toxic and can be recycled (Mehta et al., 2013). Carbon dioxide and other greenhouse gas generated during the production and the transportation of the material Concrete is an essential structural materiel which is made of a mixture of aggregate and a binder. On the other hand, cement production contributes approximately 7% of the world’s annual emissions of carbon dioxide. Calcium oxide is converted from calcium carbonate from the equation below. CaCO3 (s) + Heat -----> CaO (s) + CO2 (g) The chemical reaction and the fossil fuel combustion needed to drive the reaction process generate carbon dioxide as a by-product. Thus, by reducing the amount of cement in the concrete, the carbon dioxide emitted to the atmosphere will be reduced. This can be realized by substituting ground granulated slag from blast furnace or fly ash for cement. Slag is produced from iron blast furnace, while fly ash is obtained from the coal combustion in electrical power generation. Fly ash is less strong compared to cement. Cement has high alkalinity which is important in protecting reinforcing steel against corrosion. Normally, slag can replace cement at the rate of 15% to 40% by weight, and slag can replace cement at the rate of 15% to 25% by weight. This rate of replacement has less effect on the concrete curing, finishing and mix design (Torgal & Jalali, 2011). Life cycle cost (or whole life cost) The life cycle costing incorporates the initial cost, the costs of maintenance, costs of renovation, and daily operation over the lifetime of the building. When looking for energy efficient measures and new building options, the period of at least sixty years is used in decision making. The whole life costing includes the impacts which may not be fully reflected in the financial costing or which are difficult to measure in terms of finance – especially the impact of carbon emissions. This means that it covers the social and environmental costs related to the design, construction, operation, demolition and reuse of the building material. The flow of the materials used in constructions can be put into three life cycle phases. These include pre-building, building and post building phases (Kim et al., 1998). The pre-building phase includes the production and tranportation of the building materials, which include the extraction, manufacturing process, packaging and transport to the site of the building. This stage has got the highest potential for causing the damage to the environment. The extraction of raw materials can result in ecological damage. The production of bricks, steel and timber require clearing of forests and opening of mines (Kim et al., 1998). Mining refers to the extraction of stones and metals from the crust of the earth. The materials are not renewable and they exist in finite quantities. The refining process requires large mass of rocks to produce a small quantity of ore and can further reduce to a small quantity of finished product. Toxic wastes are produced in each step of the refining process. On the other hand, wood are renewable and can be obtained with less effect on the environment. The ecological damage relates to collection of natural resources and converting them to building materials like timber, or clearing vegetation for mining results into soil erosion, loss of life, and pollution on air and water (Torgal & Jalali, 2011). Loss of habitat results from the destruction of habitat for plants and animal species. The microclimate is destroyed. In some cases it leads to the extinction of some animals and plants. Plants filters air and water pollutants produce oxygen necessary for the survival of animals and the people, and also return moisture to the environment through respiration. Mining operations contributes to air pollution since the machinery use burned fossil fuel. For example, combustion engines produce carbon dioxide also known as green house gases as it cause global warming, carbon monoxide, nitrous oxide and sulfur dioxide which cases acid rain and can cause damage to plants and wild life (Chiras, 2004). Building phase include assembling the materials into a structure, maintenance and repair and covers the whole life of building material in the building. It should be ensured that the construction waste is reduced. Waste can also be recycled. Exposure to some materials used for building can be harmful to health. The post building phase includes reuse of the entire materials, recycling its components or discarding them. The building demolition and disposal generate waste that can be costly to the environment. Degraded materials can produce toxic waste. Some materials such as steel are reusable. The floor carpet and ceilings can provide easy access to mechanical systems and new electrical installations making renovations to be quick and cost effective (Kim et al., 1998). Energy efficiency of the operation of the building Energy efficiency is one of the important features that make a building material sustainable in the environment. The main objective of using energy efficient materials in a building is to minimize the amount of energy which can be brought to the building. The long term costs of energy operation in the construction mainly depend on the materials used to construct the building. The building material’s energy efficiency can be determined from factors like shading coefficient, R-value, fuel efficiency or luminous efficiency. The material which provides energy efficiency in the building minimizes heat transfer through the building’s perimeter, thus minimizing the energy used for cooling or heating. Quantitative efficiency analysis of the construction materials can be used to compare their properties and for determining the appropriateness for using specific materials for the construction (Torgal & Jalali, 2011). Although the day light illumination is the cheapest form of lighting, the increase in heat which accompanies solar radiation may not be required, especially during hot seasons. Shading of the transparent material reduces the heat radiation that pass through the building material. Shading coefficient is the ratio between the heats gained by the building material from the solar to the heat gained by the standard glass with double sheet strength with similar area. Shading coefficient provides the relationship between the effectiveness of sun-blocking properties of different types of glass materials, glazing patterns and shading devices. Shading devices can reduce solar heat gains during the day. Overhangs works by blocking the summer light but can allow the light to pass through during winter. Some glasses allow selective transmission of light at the same time reducing the infrared heat transmission (Calkins, 2009). R-value is an insulating value used to rate building envelopes. Better insulating materials have better R-values, but materials with low R-value are used in thicker layers to achieve similar insulating value. Individual materials such as brick and wood have specific R-values, but the R-value for composite such as materials for floors, roofing, and windows are calculated. The insulating materials vary from foams produced from petrochemicals to organic cellulose made from recycled paper. Mechanical and electrical systems account for over 50% of the annual energy costs of the building. To achieve the greatest efficiency, heating, air conditioning and ventilation systems are selected at the most commonly experienced temperatures. The equipment should be maintained regularly in order to keep them operating at peak efficiency (Bradshaw, 2006). Environmental impact of the operation of the building The building materials consumes significant amount of energy and natural resources during the manufacturing process, their use, and their disposal. This leads to generation of environmental impacts. Most of the materials used in construction are extracted from the lithosphere. The quantity of steel, concrete, insulation, glass and other materials found in the buildings increases the environmental impacts. The built environment has been known to be the biggest contributor of green house gas emission, and it accounts for up to 50% of the total global emissions of CO2. At the same time, the environmental impact by the construction in its life cycle is the same as that generated in its stage of utilization (Torgal & Jalali, 2011). Reuse of building materials saves energy and reduces the emissions of green house gases by reducing extraction and processing of raw materials as well as transporting materials over long distances. In addition, it minimizes the economic as well as reduces the impact of waste disposal on the environment. For example, landfills are built so as to reduce the green house gases generated from waste disposal (Bradshaw, 2006). The materials that are found in naturally impure environment such as ores, not only consumes energy during extraction and purification, but it also produces waste. Concrete requires more primary energy input and produces more carbon dioxide compared to timber. The energy consumption in life cycle of a steel framed building material is lower compared to concrete framed building material. But at the usage stage, the emissions and the consumption of energy by steel framed building is larger. Consequently, the overall life cycle environmental emissions and energy consumption by the concrete material is lower when compared to steel material (Chiras, 2004). Conclusion The building material provides an opportunity to the structural engineer to contribute to the sustainability of the project. Active participation in sustainable design, require the application of criteria for material selection that include economy and suitability to the specific project building requirements. The sustainable building design can be achieved through three ways: economic viability, environmental stewardship and social responsibility. The environmental cultivation id concerned with limiting emissions and controlling waste. The implementation of sustainable measures at the planning stage can significantly improve the efficiency of the building that include the construction cost, the operation, effects on the environment, and health. Further contribution to the overall sustainability of the structural project may be exploited by considering the availability, reuse, impact on the environment, efficiency, and recycled content of the material. References Bradshaw, V. (2006). The Building Environment: Active and Passive Control Systems. Hoboken: John Wiley & Sons. Calkins, M. (2009). Materials for sustainable sites: A complete guide to the evaluation, selection, and use of sustainable construction materials. Hoboken, N.J: Wiley. Chiras, D. D. (2004). Environmental science: Creating a sustainable future. S.l.: Jones & Bartlett Learning. Kim, J.-J., Rigdon, B., & National Pollution Prevention Center for Higher Education. (1998). Sustainable architecture module: qualities, use, and examples of sustainable building materials. Ann Arbor, MI: National Pollution Prevention Center for Higher Education. Mehta, M., Scarborough, W., & Armpriest, D. (2013). Building construction: Principles, materials, and systems. Boston: Pearson. Torgal, F. P., & Jalali, S. (2011). Eco-efficient construction and building materials. London: Springer Verlag. Read More

This can be realized by substituting ground granulated slag from blast furnace or fly ash for cement. Slag is produced from iron blast furnace, while fly ash is obtained from the coal combustion in electrical power generation. Fly ash is less strong compared to cement. Cement has high alkalinity which is important in protecting reinforcing steel against corrosion. Normally, slag can replace cement at the rate of 15% to 40% by weight, and slag can replace cement at the rate of 15% to 25% by weight.

This rate of replacement has less effect on the concrete curing, finishing and mix design (Torgal & Jalali, 2011). Life cycle cost (or whole life cost) The life cycle costing incorporates the initial cost, the costs of maintenance, costs of renovation, and daily operation over the lifetime of the building. When looking for energy efficient measures and new building options, the period of at least sixty years is used in decision making. The whole life costing includes the impacts which may not be fully reflected in the financial costing or which are difficult to measure in terms of finance – especially the impact of carbon emissions.

This means that it covers the social and environmental costs related to the design, construction, operation, demolition and reuse of the building material. The flow of the materials used in constructions can be put into three life cycle phases. These include pre-building, building and post building phases (Kim et al., 1998). The pre-building phase includes the production and tranportation of the building materials, which include the extraction, manufacturing process, packaging and transport to the site of the building.

This stage has got the highest potential for causing the damage to the environment. The extraction of raw materials can result in ecological damage. The production of bricks, steel and timber require clearing of forests and opening of mines (Kim et al., 1998). Mining refers to the extraction of stones and metals from the crust of the earth. The materials are not renewable and they exist in finite quantities. The refining process requires large mass of rocks to produce a small quantity of ore and can further reduce to a small quantity of finished product.

Toxic wastes are produced in each step of the refining process. On the other hand, wood are renewable and can be obtained with less effect on the environment. The ecological damage relates to collection of natural resources and converting them to building materials like timber, or clearing vegetation for mining results into soil erosion, loss of life, and pollution on air and water (Torgal & Jalali, 2011). Loss of habitat results from the destruction of habitat for plants and animal species.

The microclimate is destroyed. In some cases it leads to the extinction of some animals and plants. Plants filters air and water pollutants produce oxygen necessary for the survival of animals and the people, and also return moisture to the environment through respiration. Mining operations contributes to air pollution since the machinery use burned fossil fuel. For example, combustion engines produce carbon dioxide also known as green house gases as it cause global warming, carbon monoxide, nitrous oxide and sulfur dioxide which cases acid rain and can cause damage to plants and wild life (Chiras, 2004).

Building phase include assembling the materials into a structure, maintenance and repair and covers the whole life of building material in the building. It should be ensured that the construction waste is reduced. Waste can also be recycled. Exposure to some materials used for building can be harmful to health. The post building phase includes reuse of the entire materials, recycling its components or discarding them. The building demolition and disposal generate waste that can be costly to the environment.

Degraded materials can produce toxic waste. Some materials such as steel are reusable. The floor carpet and ceilings can provide easy access to mechanical systems and new electrical installations making renovations to be quick and cost effective (Kim et al., 1998).

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