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The UK construction industry has undergone an unprecedented change in construction technology. Modern Methods of Construction (MMC) have been invented and are increasingly being used. With regard to residential apartment blocks, up to the 1980s greater emphasis was being placed on economy of construction rather than sustainability and lifestyles. Since 1980s, factors such as (i) the speed of construction (ii) sustainability (ii) flexible use of space. The need for rapid construction has led to more use of off-site prefabrication to reduce time spent on site and increase cost-effectiveness.
The advancement of construction technology has also benefited from Government policies particularly relating to sustainable development. Perhaps one of the most significant initiatives of the UK Government to encourage sustainable construction was the setting op of the “Construction Task Force” by the Deputy Prime Minister Mr John Prescott. The task force, which comprised Sir Michael Lathum and Sir John Egan, produced a report ‘'Rethinking construction'' (Egan, 1998). This report became influential in making Government policy. Sir John Egan argued that the use of standardization, prefabrication and innovation would improve the sustainability of the construction industry in the UK. Egan also compared construction to a manufacturing process where improvements are always sustained. The report recommended the use of prefabrication and standardization in building work as a method of achieving value of money, better value for clients and other users. Such an approach is now favoured by most people in the building industry, especially in house building.
The use of modern methods of construction allows homes to be built more quickly and efficiently. Modern methods also improve site safety and supplement skilled workmanship where there may be shortages. Nevertheless, modern methods of construction have some disadvantages compared to traditional methods in that construction costs are relatively higher and also some section the public may object to futuristic building designs that go against what they are used to. Developers using MMC may need to be accredited to certain regulating authorities (such as NHBC in the UK) to ensure high quality and durability of their materials.
Prefabrication Review-History of MMC
Prefabrication was used in UK during periods of high dement, as after the world wars and the slum clearances in 1960's. The technical success of many of these systems was shadowed by social failing of high-rise living. In the 20th century about a million prefabricated houses were build. Most technical problems which were experienced were related to materials and poor workmanship. Prefabricated systems have been used in many public building in UK and other European Countries. The UK parliamentary office of Science and Technology studies showed (MORI poll, 2001) negative attitudes pre-fabrication were result of a big published disaster problem in the 60's. In mid of 1990's interest of UK was significant based system (e.g. roof trusses, steel frames etc) but the complete system of housing development was little, using relatively unskilled labour has been the predominant of UK house building.
Government reports suggest that modern methods of construction (MMC) could be part of the solution to improve the quality of housing (Baker 2003). The industry has been slow to develop innovative building technologies, according to Ball and Barrow (1999). Many studies of modern methods of construction have taken the approach of promoting off-site applications without considering all the issues (Roy et al. 2003). The off-site processes help reduce the project construction time.
Baker's review 2003
In 2003 the UK Government appointed Sir Martin Baker to review and report on the economic and social impacts of home building. The review examined affordability of homes in the UK. The Government is encouraging modern methods of construction (MMC) and increased supply of homes. One of Baker's highlights (2003) is that it challenges the home building industry to change construction to satisfy housing needs. Planning new levels of housing stock been based on demographic trends (Baker 2004). Benefits of MMC involve the manufacture of homes in factories, which is the faster construction.
The Commission for Architecture and Build Environment (CABE) has been investigate for the scope for building more quickly using modern methods of construction (MMC). The objective criteria of the audit's, they are open to criticism them also some in house building industry criticized which schemes are determined ‘'good'' or ‘'average''. In 2005 the modern methods of cost might be higher, it was report and it was possible to:
- Reduce the construction of houses on-site
- To build home up to four times with the same amount of on-site labour
- The performance should be also good as for home build in traditional way.
During the twentieth century
The new building in the UK (1996) were smaller 13% than the existing stock compared to the European countries houses that were largest that order ones. The size of a new home it was roughly 15.m2, the smallest in the Western Europe and the other European countries tend to be 20 m2 and 30 m2.
In the 1981-2001 a particular in new buildings is roughly 20% smaller than the typical pre-1919 home. A combination of social in 1950's, economical and political factors renewed to construct housing system (Boverker,2004).
Modern Methods of construction-Embodied carbon
The most serious threat to human society that has created itself is climate change. In the 1750's the global atmospheric concentrations of greenhouses gases, carbon dioxide (CO2). The building construction is a substantial contributor of global CO2. Global emissions attributable to energy use in buildings with quarter of total CO2. An important goal for the Government climate police is the reducing of energy and carbon emissions attributed to buildings.
In housing construction standard embodied energy is equivalent to a few years of energy; there are some exceptions to low energy buildings. Embodied carbon is important for low energy buildings, because less energy is used in occupation, and additional energy required for the insulation level, energy consumed in the construction materials, transport and installation. However the embodied carbon of low energy house is to contribute a better proportion of lifecycle carbon emissions during the building lifetime than a convention house.
Many of the benefits of Modern methods of construction for housing are contentious and unproven. The manufacture suggest of the Government of MMC are:
- Environment- houses can be more energy efficient, less transport of materials and produce less waste.
- Social- fewer accidents and less impact during construction.
- Economic- MMC can be build more quickly.
Overview of MMC-Types
Modern methods of construction it's a term to saw a number of construction methods. In the UK, the methods that being introduced in the building industry significant from so-called construction methods such as brick and block. The MMC was debated in the industry and was no universally agreed definition. The housing corporation that is used for its own purposes in 2003 is a published construction classification system (table 1).
Housing corporation construction
1. Off-site manufactured -Volumetric
2. Off-site manufactured -Panelized
3. Off-site manufactured-Hybrid
4. Off-site manufactured -Sub-assemblies and components
5. Non Off-site manufactured construction
Other terms of describing the MMC, is the factory building assembled, industrialized construction, innovative systems constructed on-site and pre-fabrication construction.
The sectors of the modern methods of construction have five categories used by the housing corporation: off-site manufactured volumetric, three dimensions units produced in the factory, fully fitted out before being transported in the site. The majority of off-site manufactured volumetric construction in the UK to date has been used in housing. Modules may be delivered to site in variety of forms; volumetric off-site brings all the critical activities to the structure to a factory based environment which ensures better quality control. Light steel frame off-site techniques are more used to the traditional construction methods and are used in all sectors of constructions industry. Light steel offers better quality control and reduction in waste.
Off-site manufactured-panellised construction is flat panel units build in factory, fully fitted out before being transported to site, panellised systems such as walls, roofs, floors and it consists two types of panels, open panels when assembled forms a skeleton structure and are usually timber or frame and closed panels may include internal lining materials. Off-site manufactured-hybrid is the combination of panellised and volumetric systems, is used to create the skeleton of the structure and volumetric units are used for the bathrooms and the kitchens. The environmental impact of MMC products sector were assessed including timber frame, timber frame with straw bale. A hybrid construction is a panellised system and is good design for economy. There are many manufactured of panellished systems and volumetric. Precast concrete is a construction material where concrete is cast mold which is the cured in a controlled environment, transported to the construction site and lifted into place.
Barriers of MMC
Some MMC homes builders are less expensive that the traditional methods of construction, increased cost about 7-10%. The reasons of different cost (higher) are difficult to discern because most of projects traditional masonry buildings cost widely. The cost apper high because in the MMC, there are different used of benefits such as better quality of construction, fewer accidents and reflect in project account MMC is the faster construction buildup to 50% and thus reducing labour costs. Capacity is a barrier of increasing the number of houses using MMC. In the two categories difficulties fall: factory capacity to manufacture parts and shortage of skills.
Historical overview of sustainable development
A great number of civilizations in human history it had been recognized the need of harmony between the society, the environment and the economy. More to the point, sustainable development is a very old idea that focuses, on improving the quality of life without exceeding the environmental supplies of natural resources. Unfortunately despite the predictions, the concept of sustainability gained momentum in 1980's when the problem became extremely obvious (Kenny, M., Meadowcroft, J., (1999).
In 1973 was the first time that United Nations discussed about environmental solutions in Stockholm (Langton, C., A., Ding, G., K., C., (2001). Subsequently, the ideas discussed again in the World Conservation Strategy and new strategies were adopted by the governments of fifty countries but with very small practical impact. In 1983 the United Nations created the World's Commission in Environment and Development (WCED) and in 1987 they published a report in sustainable development with the name “Our common future” also known as the Brundtland Report (Langton, C., A., Ding, G., K., C., (2001).
According to Langton, C., A., Ding, G., K., C., (2001) this report had critically signaled the rush of thinking for a second time the ways of governing and living as also the need of international coordination and cooperation. In 1992 in Rio Conference was the first time that the world's leaders discussed about the future of the planet and agreed to set out principles to achieve sustainable development. The major agreement of this meeting was a 900 page program of actions with steps towards sustainable development at international levels. In 1997 the Kyoto climate summit set targets for the industrial countries in order to bring their gas emissions 5% below 1990 levels by 2012.
Pioneering ways must be found to ensure that individual behavior and institutional structures will change targets, towards a sustainable future and will understand the consequences of inaction.
To begin with, it can be critically mentioned that the sustainable development should take into consideration the potential impacts on three main sectors, the environmental, the social and the economic; as it has been advised from Munasinghe (1993). Essentially, he advocated that, the natural habitats, the people, and the economy are interrelated and should be managed as a one. Therefore, the environmental approach it can be claimed that is so to protect the biological features, the social concept is to stabilize the cultural system and the economic approach are to maximize the income and preserve the stock of resources (Munasinghe, 1993).Ultimately, it would be imperative to append that some more important concepts in sustainable development are the futurity the equity and the irreversibility. Table 3 provides further details as per those important concepts.
Further Important Concepts:
Futurity: concern is given not only for the short term horizon, but also for the long term that affect the future generations.
Equity: Emphasis is given to the least advantaged in society in order to provide their needs and a fair treatment.
Irreversibility: Some types of environmental degradation are not possible to be restored by human ingenuity.
Source: Based on Strange, T., Bayley, A., (2008)
Objectives of sustainable development
Taking into consideration all of the above, hence explicit information that academic definitions are providing; the reviewed literature suggests that numerous previous empirical studies have been conducted based on main advantages supported as a result of the sustainable developments up to date.
Economy: Sustainable development is so to promote an economy that improves environmental quality and meet people's needs.
Energy: Reduction of energy use to suitable levels and encouragement of the consumers to spend less energy.
Land use: The main concern is to minimize the loss of rural land and to maintain the viability of town centers
Forestry: The main issue is the management of forests in a way that sustains their ecological qualities and their productive potentials.
Climate change: The key objective is the limitation of gas emissions that contribute to climate change and global warming.
Air quality: Key issues: reduction of pollutant emissions in order to improve local air quality and chemical pollution control especially in urban areas.
Mineral extraction: The main objective is the minimization of the environmental harm from mineral extraction by the efficient use of materials.
Waste materials: Sustainable Waste management can decrease the amount of waste production. The hierarchy of waste management options start with the reduction of waste materials, it then goes to the re-use and finally to disposal.
The raw materials inputs change depending upon the systems of MMC being factored. Common raw materials including metal, board materials, timber, concrete, class wool insulation. Off-cuts of these materials typically end up as waste within the factory environment. Timber is a raw and recycled material, timber panel products are usually kept separate from the clean timber as they are currently different to recycle. Steel is readily recycled material, due to its value established recycling routes. Also glass wool insulation is potentially recyclable
Raw materials are often packaged and it is this packaging that ends up as waste. Packaging wastes have various waste management routes depending on the individual manufacturer. Modern methods of construction are about better product and processes. They aim improve business efficiency, quality environmental performance, sustainability and the predictability. MMC are more broadly based that a particular focus on product MMC should make it possible to build more with the same amount of on-site labor.MMC other than open panel techniques continue to be slightly more expensive than more established techniques but the cost ranges for different techniques overlap substantially, in any particular set of conditions in MMC could be as cost-effective as brick and block or more cost effective.
Sustainable development definition
One of the most popular definitions for sustainable development was given in Brundtland report (1995):
“Sustainable is the development that meets the needs of the present without comprising the ability of future generations to meet their own needs”
(Kirby, J, O'Keefe, P., Timberlake L., 1995).
This definition indicates that an activity can be considered sustainable if it doesn't exhaust the natural resources and doesn't have serious impacts to the environment that the future generations will inherit. For instance, if the ozone layer is destroyed, if the green-house gases build up, if the natural resources are exhausted and if water and air are polluted, it is reasonably obvious that this generation don't give the ability to the next one to support their selves.
Sustainable development can be considered as:
- A theoretical framework: a method that will make the world more balanced and holistic.
- A process: techniques to apply the principles of integration to all decision.
- A target: methods of fixing the problems
Sustainable construction focuses on the issues of procurement, assembly and
Procurement: The processes of procurement introduce the objectives that the contractors must have during the construction. These objectives may include environmental commissioning. It consist matters like site planning, tendering, selection of materials, recycling and waste minimization (Smith, P., F., (2007). standards and reporting requirements.
Assembly: The assembly activities are managed by the contractors in order to contribute to the ecological performance. It consist issues as the excavation methods, the reduction of noise, the disposal of wastes and storm-water containment.
Commissioning: It gives information of how the design will operate in the future. It should relate performance specifications and maintenance methods. In order the environmental performance of the construction to be improved, the site operatives and the supervisors should have a proper training (Smith, P., F., (2007).