Background and Justification of project
Buildings are climate modifiers which provide indoor environments. These are essential to the well being and the social and economic developments of mankind. However, they are also intensive resources consumers and hence, they require enormous amount of materials and energy in their construction and maintenance. During the construction period and while they are demolished at the end of their life, buildings generate huge amount of solid wastes and various types of emissions, such as particulates, noise and various kinds of liquid effluents.
According to Hall (2003 ) and Anink (1996) the building industry accounts for around one-tenth of the world’s GDP, at least 7% of its jobs, half of all resources used and up to 40% of energy used and green house gas emission. Hill and Bowen (1997) discussed how the applications of modern technology, together with the increasing population, are leading to the rapid depletion of the earth’s physical resources. Hall (2003) also estimated that by 2025, the world population would reach 8 billion and 98% of the increase in the population would be in developing countries. With time, the construction industry is expanding and the rate of resource depletion is not sustainable.
As it can be imagined, construction materials and products are essential to life – with respect to both buildings and infrastructure. Humans spend around 80% of their time (on average) in some type of building or on roads. Construction products play a major role in improving the energy efficiency of buildings and also contribute to economic prosperity (Edwards, 2003). On the other hand, construction products also produce a considerable impact on the environment. The Worldwatch Institute estimates that 40% of the world’s materials and energy is used in buildings. However, according to Anink (1996), the construction sector is responsible for 50% of the material resources taken from nature and 50% of total waste generated. Also, Rodman and Lenssen (1993) pointed that buildings account for one-sixth of the world’s freshwater withdrawals, one-quarter of its wood harvest, and two-fifths of its material and energy flows. The impact of construction products relative to the overall lifetime impact of a building is currently 10-20%. For infrastructure this value is significantly higher, greater than 80% in some cases.
In Mauritius, nearly all the main resources in a building are imported, e.g. steel and cement. An average of 600 000 tonnes of cement are imported annually in Mauritius. As our country is currently going through a boom in the construction sector, the figures are expected to increase. The price of crude oil has more than doubled on the world market during the past years. This has had a direct impact on nearly all the construction materials which are imported and produced locally. While choosing for construction materials, many do not think about the impacts that the material have on the environment.
The environmental impacts of building materials are increasing day by day. Therefore, environmental impacts have become an increasingly important consideration in selecting building materials for the construction. Consequently, life cycle assessment has become an important tool in analysing natural resources and emissions generated in manufacturing processes. Winistorfer and Zhangjing (2004) said that life cycle assessment refers to the analysis of the environmental impact of a product through every step of its life. It includes environment impacts while the product is manufactured, used and disposed. The objective of a life cycle analysis is to quantify environmental influences of a product through input and output analysis.
Aim and Objectives
The aim of the project was to calculate all the resource energy and associated greenhouse gas emissions linked to construction of a typical residential house in Mauritius. Simapro Life Cycle Analysis software was used to calculate all the resource energy and greenhouse gas emission from the building.
The objectives were to:
- quantify all the resources required for the construction of the typical residential house
- estimate the weight of the building
- minimise the use of resources in building thereby reducing the greenhouse gas emission and ensuring a cleaner production.
To satisfy the aim and objectives of the project, a virtual house was selected to carry out the analysis. The house used was obtained from the central statistics office. It represents the most common type of building in Mauritius. The size of the house is 128m2. All the quantities of materials used for the construction of the building were calculated. Using Simapro life cycle assessment software, the energy requirement and CO2 emission of each material was obtained. Also, the weight of the house was calculated using the unit weight of reinforced concrete and concrete blocks.
Structure of Report
A literature search was done and the findings were included in chapter 2. The latter describes how the building consumes all the different resources, energy requirements and the environmental impacts of building. Also, the benefits of sustainable building and of recycling waste, in order to recover the energy, were discussed. A detailed methodology, which was adopted to achieve the aim and objectives of the study, was described in chapter 3. The key results and discussions were presented in chapter 4. Finally, conclusions, recommendations and further works were dealt with in chapter 5.
Building: direct consumption of resources
There is growing concern that human activity is affecting the global and local ecosystem severely enough to potentially cause permanent changes to some ecosystems and potentially cause them to crash. Boyle (2005) suggested that there must be a reduction factor of 20 to 50 in resource consumption and efficiency in order to achieve technologies which are sustainable.
Sustainable technologies will be particularly significant to the construction industry which is a major consumer of resources. The pie chart below gives a repartition of all the primary materials resources used in the construction industry in 1998.
Figure 2.1 – Repartition of primary resources in the construction industry (Source: Construction Resource Efficiency Review, 2006)
Despite the fact that every house makes use of different quantity of resources, according to US DOE Energy Efficiency and Renewable Energy Network, a standard wood-frame house uses 4047 m2 (one acre) of forest and produces 3-7 tonne of waste during construction. Lippiatt (1999) stated that building consumes 40% of the gravel, sand and stone, 25% of the timber, 40% of the energy and 16% of the water used globally per year.
Boyle (2005) estimated that in UK itself, about 6 tonnes of building materials were used annually for every member of the population. Much of the waste and consumption of resources occurred during the extraction and processing of the raw materials. For example, mining requires water and energy, consumes land and produces significant quantities of acidic contaminated gas, liquid and solid wastes (Boyle, 2005). A second example which can be used is that of timber. The cultivation of trees requires significant space for cultivation and amount of fertilizers. Moreover, the harvesting and processing phases of timber make use of considerable amounts of energy. Trees are also grown in plantations which require old-growth forest and significantly reduce biodiversity.
Energy is also used extensively in the transportation of raw materials. Fossils fuels are used for the transportation, extraction and harvesting of the material, thereby releasing greenhouse gases and a range of air pollutants. Processing of metals and mineral often results in major gas emissions. The concrete industry is a major producer of carbon dioxide whereas on the other hand, aluminium smelting produces perfluorocarbons (Boyle, 2005). These two are very powerful greenhouse gases. According to the Construction Resource Efficiency Information Review (2006), emissions to the air by the construction industry in 1998 were just over 30 million tonnes in total, of which over 97% was carbon dioxide. Of the 30 million tonnes of emissions, over 70% came from mineral extraction and product manufacture.
The table below shows the total carbon dioxide equivalent emissions generated by the construction industry in UK.
Table 2.1 – Carbon dioxide equivalent emissions generated by the construction industry in UK (Source: Construction Resource Efficiency Information Review, 2006)
Emission generated by:
Tonnage (Kt )
Mineral extraction, product and material manufacture
Transport of product and material
Transport of secondary and recycled product
Construction and demolition site activity
Transport related to construction and demolition site activity
Transport of waste from product and material manufacture
Transport of construction and demolition waste
Total CO2 equivalent emissions to the atmosphere
As it can be seen, from Table 2.1, a total of 28 327 Ktonnes of CO2equivalent emissions were generated by the construction industry in UK and much of these emissions occurred during the mineral extraction and product and material manufacture.
Over the lifespan of a building, the material will have to be maintained and stored in good condition whereas, in some cases, replaced. Every five to fifteen years, exterior coatings, guttering, piping, walls, and flooring will require repair or replacement. By effective maintenance, requirements for replacement are reduced by a significant amount. The decisions here are not taken by the builder or designer regardless of the original design. Concerning the material used for the repair and the maintenance of the building, it is the owner who takes the decision.
During the lifespan of a building, the overall investment of resources into the building needs to be considered (Boyle, 2005). Buildings can be constructed and designed in such a way that they can last for more than hundred years. Additionally, many traditional buildings are designed in such a way that they can last beyond 200 years (Morel, 2001). However, many designers are now planning buildings for a lifespan of only 50 years or even less despite using durable materials requiring minimal maintenance. Such materials reduce the requirement for repairs or replacement. Hence, simply designing and maintaining a building for 400 years rather than 50 can potentially reduce its environmental effect from material resources by up to a factor of 4 (Boyle, 2005).
Energy requirements of a building
Cole and Carnan (1996) found that the energy that is consumed during the life cycle of a residential building includes energy used in producing building materials and constructing the structure. Also, energy is used in occupying and maintaining the building, and in demolishing or deconstructing the structure at the end of its serviceable life. According to Cole and Carnan (1996), the energy consumed in building can be classified in three categories:
- energy to initially produce the building;
- energy to operate the building, and;
- energy to demolish and dispose of the building at the end of its effective life.
During the extraction, processing and transportation of material as well as during the construction as mentioned earlier large amount of energy is consumed. Morel et al. (2001) found that costs could be reduced by more than a factor of 6 during construction by the use of energy of local materials. The local materials studied by Morel et al. (2001) included rammed earth, stone, timber which were compared to the use of imported concrete. Consequently, Morel et al found that the imported concrete required significant energy for processing. Treloar et al. (2001) found that, by using a concrete binder, rammed earth had an energy load equivalent to that of a brick veneer construction due to the energy required in processing the cement.
Boyle (2005) stated that energy is the major resource consumed in buildings and 90% of the energy consumption is over the operational lifespan of the building. Therefore, significant decrease in energy consumption assists in reducing the resource consumption and improving efficiency. Although a house can be designed to a totally self-sufficient condition for energy and water, much depends on the location, that is, the climate, the availability and potability of local water sources as well as the attitude of the user. The designer or builder can incorporate some energy saving devices and design such a water heater, passive heating, and composting toilets, which are suitable for local conditions. Furthermore, such devices and designs will only be incorporated if a significant profit can be generated. Many developers resist including energy- saving measures unless they are required by local councils or are considered essentially by buyers in the local community. Cole and Kernan (1996) found that the energy used to heat, cool, provide artificial lighting, and power typically used appliances in buildings accounts for more than 30% of Canada’s national energy use. Approximately two-thirds of this consumption is attributed to residential buildings and the remainder to commercial buildings. The US DOE Energy Efficiency and Renewable Energy Network estimated that, the annual average energy consumption for one story concrete building, the annual average energy consumption is 63GJ.
However, Zydeveld (1998) pointed out that up to 80% savings in heating water and improving the indoor air quality and thermal comfort could be made in the Netherlands with the inclusion of passive solar design with an additional 10% cost in construction. Therefore, savings of 90% could be achieved. Four major design principles enabled architects and builders to incorporate passive solar design into their buildings: solar orientation; maximizing the solar gain through low surface loss and high internal volume; high mass within the insulation and avoiding of shading.
The rise in use of material in the low energy building can, however, mean that there is an increased consumption of material and energy overall. Thormark (2002) discovered that up to 45% of the total energy used is in the embodied energy in a low-energy building and that such a building could have a greater total energy use than that of a building with a higher operating energy consumption. Besides, he also said that 37-42% of the embodied energy could be recovered by recycling of materials.
According to an unknown author (2007), Embodied Energy is the amount of energy that has gone into the making of a material or things made with materials. A very high percentage of the world’s energy is derived from fossil fuels which, when burnt, release vast amounts of CO2. As the production of energy from fossil fuels is environmentally unfriendly, materials and things that have a lower embodied energy are more sustainable than those with a higher embodied energy.
On average, 0.098 tonnes of CO2 are produced per gigajoule of embodied energy (Sustainable built environment 2007).
Source: Sustainable Technologies (1996)
Figure 2.2: Embodied Energy of the different building materials
The embodied energy per unit mass of materials used in a building varies enormously from about two gigajoules per tonne for concrete, to hundreds of gigajoules per tonne for aluminium.(Figure 2.2). The reuse of materials commonly saves about 95% of embodied energy which could otherwise be wasted (Sustainable Built Environment 2007).
According to Fichtner Report (1999), in Mauritius, steel is the only waste material generated from the construction industry which is recycled, implying that most of the embodied energy of the materials is wasted.
Resource Efficiency in a building
According to the report “Construction Resource Efficiency Review” (2006), resource efficiency is about the sustainable use of resources. Indeed, there should be effective use and management of all the resources available to the industry while at the same time optimising output and profit. There is much emphasis on the use of all the physical resources (water, energy, etc) and materials used in the production and operation cycle. As minimum resource is used in the manufacture of the product, profits can be made by increasing productivity. Resource efficiency can also be achieved by reducing the wastes.
As far as the construction industry is concerned, there is a need to focus on sustainable consumption of resources. Buildings can be built with fewer resources while looking at the same time at the impacts of the building on the environment.
Buildings have a tremendous impact on our environmental quality, resource use, human health and productivity. According to Nicholas S. (2003), sustainable building meets current building needs and reduces impacts on future generations by integrating building materials and methods that promote environmental quality, economic vitality, and social benefit through the design, construction and operation of our built environment. Sustainable building, also referred as green building, involves the consideration of many issues, including land use, site impacts, indoor environment, energy and water use, lifecycle impacts of building materials, and solid waste.
Benefits of Sustainable Building
There are a number of environmental, social, and economic benefits which we can enjoy from a sustainable building. Miriam L. (1999) gives some benefits of sustainable building to the environment, which are as follows:
- air and water quality protection
- soil protection and flood prevention
- solid waste reduction
- energy and water conservation
- climate stabilization
- ozone layer protection
- natural resource conservation
- open space, habitat, and species/biodiversity protection
Also, sustainable building can have other benefits for designers, contractors, occupants, construction workers, developers, and owners. These benefits include:
- Improved health, comfort, and productivity/performance
As mentioned earlier, people spend 80 % of their life in some buildings. It is reported that 30 % of new and remodeled buildings worldwide may be linked to symptoms of sick building syndrome (WHO 1984). Particular Symptoms are:-
- Eye, nose or throat irritation
- Dry cough
- Sensitivity to odors
Sick building syndrome (SBS) is normally caused by fungi and bacteria that build up because of inadequate fresh air ventilation in structures. Therefore, improving the indoor environment of the building can reduce the effect of SBS.
Lower construction costs
The cost of the building can be lowered by reducing the use of material and saving on disposal costs because of recycling. For example, recycled aggregate can be used as filler material.
Lower operating costs
As discussed earlier in chapter 2.10, the use of energy can be reduced in a building by designing the building such that it gets maximum sunlight, and in so doing, cutting down expenses concerning electricity. This has a great impact for people with low income, who spend much of their salary in paying utility bills.
Life Cycle Assessment
“….Life Cycle Assessment is a process to evaluate the environmental burdens associated with a product, process, or activity by identifying and quantifying energy and materials used and wastes released to the environment; to assess the impact of those energy and materials used and releases to the environment; and to identify and evaluate opportunities to affect environmental improvements. The assessment includes the entire life cycle of the product, process or activity, encompassing, extracting and processing raw materials; manufacturing, transportation and distribution; use, re-use, maintenance; recycling, and final disposal….” Guidelines for Life-Cycle Assessment: A ‘Code of Practice’, SETAC, Brussels (1990).
There are four main components of LCA, which are as follows:
– Goal definition and scoping:
Identify the LCA’s purpose and the expected products of the study. Also, he needs to determine the boundaries and assumptions based upon the goal definition
– Life-cycle inventory:
Quantify the raw material and energy inputs during each stage of production. Moreover, environmental releases are also taken into account.
– Impact analysis:
Assess the impacts on human health and the environment associated with energy, raw material inputs and environmental releases quantified by the inventory.
Evaluate opportunities to reduce energy, material inputs, or environmental impacts at each stage of the product life-cycle.
For this project, only the environmental impacts (carbon dioxide emission) and energy used from the manufacture of all the materials utilised in the construction of a typical residential house were considered.
The construction energy generates an enormous amount of waste. Rogoff and Williams (1994) pointed out that in the USA, wastes from the construction industry contributed to approximately 20 %, in Australia 30% and in UK more than 50 % of the overall landfill volumes in each country. The Building Research Establishment (1982) has defined waste as the difference between materials ordered and those placed for fixing on building projects. Serpell and Alarcon (1998) defined construction waste as any material by product that does not have any residual value.
But this is not true for the construction and demolition waste as much as the waste can be reduced or recycled. By reducing the level of waste in the construction industry, it benefits the environment and lowers the cost of the project.
Bossink and Brouwers (1996) estimated that about 1-10% by weight of the purchase construction material leaves the site of residential projects as waste. However Guthrie et al. (1998) found that at least 10 % of all the raw materials which are delivered on most construction sites are wasted through damage, loss and over-ordering.
A study carried by Dabycharun (2004), pointed out that a residential house in Mauritius generates about 0.2-0.5 tonne/m2 of waste. He carried out questionnaire interview in order to get this figure. However, the Fichtner report (1999) states that during the construction of an average private house of 140 m2, 8-10 tonne of mixed waste are generated.
Skoyles and Skoyles (1987) identified two main kinds of building construction waste and finishing waste. Structure waste consists of fragments, reinforcement bars, abandoned timer plate and pieces which are generated during the finishing stage of a building. For example it comprises of surplus cement motar arising from screeding scatters over the floors inside the building.
There are two distinct procedures in minimising the amount of in landfill sites through the construction process. The first one is to reduce the amount of waste generated through source reduction techniques both on site and during the design and procurement phases of a building project. The second procedure is to improve the management of the unavoidable waste generated on site. In managing the unavoidable waste, there are three options in order of preference. They are as follows:
The balance between the three will depend upon the nature of the materials wasted, legislative requirements for the specific materials and the cost effectiveness of each option. The cost will in turn depend upon the availability of reusing and recycling options and the opportunities for reuse on a specific project.
Recycled materials, while requiring transportation and reprocessing, consume significantly fewer resources compared to the extraction and processing of raw materials. This is particularly true for metal such as iron, copper and aluminium. These metals can be reproduced to a quality equal to that of raw material processing. Both concrete and timber can be recycled or reused but with the defect that the quality of the final product is often diminished. By crushing concrete, we can reuse it as an aggregate for some purposes, particularly like paving (Boyle, 2005). But, it was found by Millard and al. (2004) that from the recycled aggregate found in the construction and demolition waste, concrete blocks can be manufactured. Also, coarse recycled aggregates can be used in new concrete (Limbachia, 2004). Good grade timber can be used in the making of furniture. It is strongly stated not to use supporting timber since it is difficult to determine whether a used timber beam has stress cracks or other weak points. In other countries, plastics can be recycled into a number of construction products, including tiles, lumber, heating and wire insulation and carpet. According to Huang and Hsu (2003), each year in Taiwan over 10×106 tonnes of construction material are extracted for their usage and more than 40×106 tonnes of construction waste are disposed without recycling. Significant amounts of asphalt were present in the waste. However, if it was recycled, this would have decreased the amount of asphalt which was imported. Thormark (2002) pointed out that recycled concrete, clay brick and lightweight concrete can meet the total need for gravel in new houses and in renovation.
Materials and Methods
The next part of the dissertation was the methodology. In this section, an analysis was carried out on the different resources used for the construction of a single-storey house and the CO2 emission from each of the different resources. Therefore, a house had to be selected to carry out the analysis
Selection of a typical house
The house model used for the analysis was basically a virtual detached house which occupied a space of 128.30 squares metres floor area. The floor area was measured at plinth level to the external face of the external wall. The plan of the typical house model was obtained from the Central Statistics Office which was originally provided by the Mauritius Housing Company Limited. The house represented the most common type of residential house in Mauritius. The plan of the house is found in appendix A.
The building constitutes of two bedrooms, a living-dining room, a kitchen, a toilet, a bathroom, a verandah and an attached garage. It was assumed to be built up of concrete block walls, reinforced concrete flat roof, internal flush plywood doors, glazed metal openings, screened floor and roof, tiling to floor and walls of W.C, and bathroom and kitchen worktop; the ceiling and walls were rendered and painted both internally and externally.
It should also be noted that in the event the single-storey building would need to be converted into a two-storey house, an additional provision of more substantial foundation and of stub columns of the roof has already been made.
Calculation of different resources
Various materials and other resources were needed during the construction of the house.
These can be broken down in different input categories. The input categories (different components) for the construction comprised of labour, hire of plant, materials and transport. The materials were further broken down into hardcore fillings (remplissage), cement, sand, timber for carpentry and joinery, metal openings, ceramic tiles, glass and putty, plumbing, sanitary installation, electrical installation and other miscellaneous expenses.
The weightage of the components, shown in table 3.0, was calculated by a private firm of Quantity Surveyors for the Central Statistics Office’s use. The firm had identified nineteen stages through which the construction of the house had gone through. The cost for each stage was calculated. Detailed cost of each inputs in terms of plant, labour, materials and transport that go into the construction of typical residential house were calculated. According to the Statician, Jagai D. (pers. Comm., 19 November 2007), the construction of the single storey building, in the year 2001, was estimated by the quantity surveyor to be Rs 550,000. the weight was calculated so that each input category represented a fraction of the price for the residential building.
Table 3.0 – Weightage of different Input categories
(Source: construction price index,2007)
Weight / %
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