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Int. J. Environment and Sustainable Development, Vol. 10, No. 4, 2011
A comparative analysis of building materials for sustainable construction with emphasis on CO2 reduction Shahriar Shams*, Kashif Mahmud and Md. Al-Amin Department of Civil and Environmental Engineering, Islamic University of Technology (IUT), Board Bazar, Gazipur-1704, Bangladesh E-mail:
[email protected] E-mail:
[email protected] E-mail:
[email protected] *Corresponding author Abstract: Building contributes almost 40% of CO2 emissions and is a major contributor to the green house gas (GHG) emissions. Different types of construction materials possess a wide variation of embodied energy and emit CO2 at different magnitudes during its life cycle. Selection of appropriate construction materials can considerably cut down CO2 emissions and make our buildings more sustainable and energy efficient. The study is an attempt to address the issues of sustainable construction and how its selection of construction materials can reduce CO2 emissions and play an important role in reducing the impact of climate change directly or indirectly. A case study for a typical house having 90 sq. m. of plan area was analysed to see the variation of CO2 emission based on altering the types of construction materials to be used. It has been observed from the case study that construction materials like aluminium and steel should be less encouraged due to their higher CO2 emission rate as compared to glass and timber. Keywords: building materials; climate change; embodied energy; sustainable construction. Reference to this paper should be made as follows: Shams, S., Mahmud, K. and Al-Amin, M. (2011) ‘A comparative analysis of building materials for sustainable construction with emphasis on CO2 reduction’, Int. J. Environment and Sustainable Development, Vol. 10, No. 4, pp.364–374. Biographical notes: Shahriar Shams is currently teaching as an Assistant Professor in the Department of Civil and Environmental Engineering at Islamic University of Technology (IUT), Gazipur, Bangladesh. He received his PhD from the University of Manchester (UK) in 2008 and MSc in Environmental Engineering and Sustainable Infrastructure from Royal Institute of Technology (KTH) Sweden. He has published a number of peer reviewed international journal and conference papers related to water and environmental issues. Kashif Mahmud is an Assistant Professor in Civil and Environmental Engineering Department of Islamic University of Technology (IUT), Gazipur, Bangladesh. He received both his MSc and BSc in Civil Engineering from Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh. His main research interests are solid waste management, landfill
Copyright © 2011 Inderscience Enterprises Ltd.
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leachate management and characterisation, application of biological and chemical processes in waste water treatment, leachate recirculation modelling, sustainable developments, etc. He has published several research papers in international refereed journals and conference proceedings. Md. Al-Amin is currently working as a Lecturer in the Department of Civil and Environmental Engineering at Islamic University of Technology (IUT), Gazipur, Bangladesh. He received his Bachelor degree in Civil Engineering from Bangladesh University of Engineering and Technology in 2008. He has published couple of papers in international journal and conference.
1
Introduction
The concept of sustainability in building and construction has evolved over many years. In fact, the United Nations Centre for Human Settlements (Habitat, 2001) acknowledges that housing is now universally recognised as a human right and that effort to implement this right must be strengthened and accelerated. Furthermore, the success and progress of human society depends on physical infrastructure, and a nation’s economic strength is reflected in its infrastructure assets (Hudson et al., 1997). With almost 60% of world population expected to be living in urban areas by the year 2030 (Syal et al., 2006), massive construction activity is taking place globally. Sustainable construction is a way for the building industry to move towards achieving sustainable development, taking into account the environmental, socio-economic and cultural issues. Specifically, it involves issues such as design and management of buildings, materials and building performance, energy and resource consumption – within the larger orbit of urban development and management (Miyatake, 1996; Ding, 2008). It requires optimisation of environmental impacts such as water use, energy flow and waste output in addition to CO2 emissions from the building. Bangladesh is recognised worldwide as one of the countries potentially most vulnerable to the impacts of global warming and climate change (ADB, 1994; Ali, 1996, 1999; IPCC, 2001; World Bank, 2000; Piguet, 2008; Climate Risk Index, 2010). This is due to its unique geographic location, dominance of floodplains, low elevation from the sea, high population density, high levels of poverty, and overwhelming dependence on nature, its resources and services. Global warming has caused fundamental changes to our climate. According to the IPCC (2001), a 45 cm sea-level rise could cause a potential land loss of 10.9% and a one meter sea-level rise a loss of 20.7%. The UNDP (2007) predicts that 11% of the population will be directly threatened by a one meter sea-level rise. The fast growing mega city like Dhaka is more exposed due to its unplanned urbanisation, rapid population growth and massive boom in construction sectors, improper management and planning. Therefore, the study is an attempt to address the issues of sustainable construction and what approaches needs to be implemented for the developing cities like Dhaka based on existing geophysical, socioeconomic and climatic condition.
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The environmental impact of construction
Despite the benefits of construction, its activities can be a major source of environmental damage through depletion of the natural resource base, degradation of fragile eco-zones, chemical pollution and the use of building materials harmful to human health (Earthwatch, 2009). The design, construction, and maintenance of buildings have a negative impact on the environment and natural resources. Globally, buildings account for the following impacts (Augenbroe et al., 1998): •
One-sixth (17%) of the world’s freshwater withdrawals.
•
One-quarter (25%) of its wood harvest.
•
Two-fifths (40%) of its material and energy flows.
•
nearly one-quarter (25%) of all ozone-depleting chlorofluorocarbons (CFCs) are emitted by building air conditioners and the processes used to manufacture building materials. A report from the Worldwatch Institute stated that building construction accounts for 55% of non-fuel wood use, and worldwide, buildings account for 40% of energy and materials use Roodman and Lenssen (1995). The energy consumption in the buildings both residential and commercial is likely to increase in the next 30 years, particularly in the developing countries as shown in Figure 1. While apart from USA the developed countries energy consumption will increase very steadily. This steady increase in developed countries indicates how they are using energy efficient materials and technologies in the built environment. The embodied energy and CO2 emission of common construction materials are shown in Table 1.
Figure 1
Building energy projection by region 2003–2030 (see online version for colours)
Note: *Energy use from marketed sources. Source: Energy Information Administration (2006)
A comparative analysis of building materials for sustainable construction Table 1
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Embodied energy and CO2 emission of common construction materials
Materials
Embodied energy MJ/kg
CO2 emission kg/kg
Aggregate
0.1
0.16
Concrete
1.3
0.1311
Brick
2.5
0.189
Plywood
10.4
4.2
Glass
30.3
0.748
Aluminium
227
9.964
Steel
32
2.95
PVC
70
2.6904
Plastics
61
2.2
Timber
3
0.003
Lime
6
1.352
Cement
5.8
0.9638
Gravel and sand
0.5
0.0018
5
0.349
Ceramics
Source: Kilbert (2007) and Mulavdic (2005)
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Sustainable construction
A good building practices offer an opportunity to create environmentally-sound and resource efficient buildings by using an integrated approach to design. Sustainable building is the process of producing a constructed facility that encompass ultimate energy efficiency, forward-thinking resources management, and general sustainable construction (Rajgor, 2004). It requires an integrated team; combining a wide range of different specialists through in-depth collaboration so that the complexity of trade-offs between architectural features, value and cost, building services and other factors can be reached (Sorrell, 2003). The characteristics of sustainable buildings include: •
resource conservation, including energy efficiency, renewable energy, and water conservation features
•
consideration of environmental impacts and waste minimisation
•
creation of a healthy and comfortable environment
•
reduce operation and maintenance costs and use of environment friendly construction materials
•
contribute to overall quality of life.
368 Figure 2
S. Shams et al. Location of DOHS Baridhara (see online version for colours)
Source: Goggle Map
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Study area
The developing city like Dhaka is having an annual growth of 12% in construction sector which contributes 3.7% of GDP (Mintoo, 2006) and employs 1.6 million people. Today, real estate and construction industry is the biggest of all the locally run industries and contributing 14.50 billion BDT (US$231 million) (BBS, 2006) annually. A survey was conducted in DOHS Baridhara in the year 2009 to identify the number of houses being built and to estimate amount of CO2 based on different types of materials used. DOHS Baridhara is located on the northern part of Dhaka city which is 2 km away from the airport (Figure 2). The area is also close to the diplomatic zone and an affluent community lives there. The average temperature of DOHS Baridhara is 0.5°C to 1°C higher than its surrounding area like Gulshan and Banani as observed during the survey. The most of the heat is generated from the buildings as there are very few trees or vegetation in the area. The justification for considering this area is that the buildings are built very recently (last 20 years) and many are still in the construction phase. There is an opportunity to look at the building materials that are widely used. There are 654 houses in DOHS Baridhara with estimated population of 6,000. Of the total area, 98.2% plot areas are already occupied by houses and rest of them are still vacant plots. Almost 36% houses are still under construction. Average plot area is 3,600 sq. ft. and average covered area is 2,600 sq. ft. Table 2
Estimate of the materials required for five story building
Sl. no.
Name of the item
Unit
Quantity
1
Reinforcement
kg
50,441
2
Cement
bag
3
Sand
4
Brick a
Picket (for Khoa)
5,204 32,957
nos
13,500
b First class
nos
109,048
5
Stone
cft
14,527
6
Door Wooden
sft
1,800
Plastic
sft
900
Grill
sft
4,010
Aluminium
sft
4,010
7
Window
Tiles work
sft
21,252
8
Painting (plastic)
sft
72,075
9
Painting (weather coat)
sft
9,165
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Results and discussions
The analysis of building materials were based on the quantity used assuming the house is a five story building. It is estimated for an average of 2,600 sq. ft. floor area, a five story building would produce approximately 5,128,640 MJ embodied energy and 412,254 kg CO2. This has been calculated based on the quantity of materials required for construction as shown in Table 2. The estimated materials are converted into weight and then using the embodied energy and CO2 emission for specific materials as given in Table 1, the total amount of embodied energy and CO2 for the five story building is calculated (Table 3). Table 3 Item
Embodied energy and embodied CO2 for a five story building using typical combination of construction materials in the study area Description
Embodied energy MJ Embodied CO2 kg
1
Backfill (using general sand)
87,653
4,383
2
Flat soaling (using common bricks)
117,695
8,631
3
Cement concrete work using general cement
91,683
11,431
4
Brick works using common bricks
914,349
67,052
5
Tiles work using ceramic tiles
272,184
17,843
6
Plastering work (mortar using general cement)
227,296
33,249
7
Painting (double coat)
168,214
8,741
8
Door (wooden + PVC)
1,124,227
39,181
9
Window (aluminium framed)
875,200
44,640
10
Reinforced concrete (using general cement)
1,250,138
177,103
Total
5,128,640
412,254
Table 4 Item
Embodied energy and embodied CO2 for a five storied building using alternative combination of construction materials in the study area Description
Embodied energy MJ Embodied CO2 kg
1
Backfill using general sand
87,653
4,383
2
Flat soaling using common bricks
27,854
3,139
3
Cement concrete using cement with 50% fly ash
66,679
6,906
4
Brick works using common bricks
914,349
67,052
5
Tiles work using marble tiles
117,623
6,665
6
Plastering work (mortar using cement with 50% fly ash)
113,648
16,292
7
Painting (single coat)
84,932
4,370
8
Door (laminated veneer lumber)
173,577
9,318
9
Window (timber framed)
57,600
2,960
10
Reinforced concrete (using cement 50% fly ash)
833,426
106,493
2,477,339
227,579
Total
A comparative analysis of building materials for sustainable construction Figure 3
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Variation of embodied energy and embodied CO2 of construction materials made from cement with cementitious (fly ash and balst furnace slag) (see online version for colours)
The materials for construction have a significant impact on the embodied energy and embodied CO2 of a building. Another calculation has been made for the same five storied building using alternative combination of building materials (Table 4). In this calculation
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the materials are selected on the basis of their embodied energy, embodied CO2 and availability. The analysis revealed that we can reduce approximately 52% of total embodied energy and 45% of total embodied CO2 of a building only by using building materials with low embodied energy and low embodied CO2. The principal materials for construction (cement concrete, mortar for plastering, reinforced concrete) in the study area are made from general cement (Type I cement as per Bangladesh Standard BDS EN 197-1:2003). The study shows that there is a significant reduction in embodied energy and embodied CO2 if the general cement is replaced with other cementitious materials like fly ash or blast furnace slag (Figure 3). These types of cement (Type-II and Type-III as per Bangladesh standard BDS EN 197-1:2003) are available in Bangladesh with similar physical and mechanical properties as type-I cement. By replacing type-I cement with type-II or type-III cement the embodied energy and embodied CO2 can be reduced to 23% to 35% and 22% to 45% respectively. Therefore, selection of materials can significantly reduce embodied energy and CO2 which play an important role in reducing the impact of climate change resulting from emission. The sustainable buildings should emphasis on use of recycled materials like bricks and concrete, natural ventilation using mixed mode design. Mixed mode design is a concept where mechanical and natural ventilations are provided for optimum comfort condition, which is 26 degree Celsius. The dwellers are encouraged to use water saving technologies through aerated and self-closing faucets. Currently it is not clear whether energy-efficient products and services can be competitive with existing, less-efficient versions, because of reluctance among potential buyers to pay an adequate price. This reluctance is based on the value proposition not having been fully developed and communicated. The study identified that there is a lack of information among the residents of the study area regarding energy use and the concept of sustainable buildings. There is also a lack of leadership from the real estate developers, professionals or politicians to promote sustainable construction approaches in the country. Also very few professionals have know how or hand in experience in constructing sustainable buildings. In DOHS Baridhara, most of the buildings are built very recently with expensive fittings and building materials like using glass, aluminium and marbles, aluminium, wide glasses, etc. which produce more embodied energy in their life cycles. The owners as well as real estate developers have given priorities more on atheistic value and used widespread building materials imported from abroad instead of using local materials. Therefore, the main challenges are stimulating an appropriate design approach, reconciling this with the concept of sustainable buildings to overcome behavioural barriers.
6
Conclusions
Selection of appropriate construction materials can considerably cut down CO2 emissions and make our buildings more sustainable and energy efficient. The analysis of a five-story building having an area of 90 sq. m. demonstrates that we can reduce approximately 52% of total embodied energy and 45% of total embodied CO2 by altering the building materials with low embodied energy and low embodied CO2. It has been observed from the case study that construction materials like aluminium and steel should be less encouraged due to their higher CO2 emission rate as compared to glass and timber. The case study shows that use of bricks rather than using ceramics can cut down CO2 emission by one third. This seems quite promising; hence, many refurbishment
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works for high-rise building could be adapted to the cities where there is a demand for high-rise buildings with emphasis on materials which emits less CO2 in its life cycle. A good building should incorporate as many sustainable, local materials as possible into its construction – to support local economies, to avoid the high energy and financial costs of long-distance transportation, and to fit in with local aesthetics. The fast growing cities like Dhaka need immediate attention so that buildings are designed for maximum efficiency with optimum use of resources and lesser impact on environment. It is also recommended that the real estate developers working with construction industries needs to be assessed and ranked annually based on the concept of sustainable buildings. It is recommended that sustainable construction processes should promote the increased use of energy-efficient designs and technologies and sustainable utilisation of natural resources. It should provide financial incentives to promote recycling of energy-intensive materials in the construction industry. The use of construction materials and products that create pollution during their life cycle should be discouraged by imposing pollution tax.
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