Sustainable construction refers to the adoption of building designs, construction methods and materials that are environmentally friendly. It also means using materials and resources that have sustainable supplies and are readily available from many sources. Through Sustainable construction, we will do our part to optimize the use of natural resources via recycling and reuse of materials. This will also reduce our dependence on raw building materials, given the current disruption in the supply of concreting sand and granite.
Construction industry is commonly one of the largest industries in both developing and developed countries in terms of investment, employment and contribution to Gross Domestic Product. Consequently, the impact of the construction industry on the environment is expected to be considerable particularly as far as the loss of soil and agricultural land, the loss of forests and wildlands, air pollution, and the loss of non-renewable energy sources and minerals are concerned.
According to buildings, contribution to total environmental burden ranges between 12.42% of the eight major environmental stressor categories: use of raw materials (30%), energy (42%) water (25%) and land (12%) and pollution emission such as atmospheric emissions (40%), water effluents (20%) solid waste (25%) and other releases (13%). Buildings and building construction services account up to 66% of total energy consumption.
Principles of Sustainable Construction
The above definitions of sustainable construction are all framed towards creating a healthy built environment through resource efficient and ecologically sound processes, preservation of ecosystems and maintenance of natural balance between development and carrying capacity of this planet. The key principles upon which the above definitions have been phrased can be summarised into the main principles of sustainable construction. A range of models detailing principles of sustainable construction will now be briefly reviewed.
Hill and Bowen aggregated the principles of sustainable construction into four pillars – social, economic, biophysical, and technical. These are supplemented with a set of over-arching, process-oriented principles. “These process-oriented principles suggest approaches to be followed in deciding the emphasis to be given to each of the four pillars of sustainability, and each associated principle, in a particular situation”.
Palmer classified the principles underlying sustainable development as futurity, environment, public participation and equity. These were adopted as the principles of sustainable urban development by BEQUEST.
Achieving Sustainable Construction
Sustainable construction starts with planning and design. The developer’s and designer’s roles are therefore critical. However, as sustainable construction involves prefabricated products, it would be helpful to bring in relevant suppliers and specialists early in the design stage. Implementation down the entire construction value chain is also important. There is a need for sharing of knowledge and expertise in design and the use of such materials. Equally critical is the building of capabilities and skills in construction and installation. The performance of such buildings in safety and quality should remain high. As the use of steel in construction has been relatively low in the industry, the gearing up and development of such knowledge and capabilities will be given priority.
Design professionals (Architects and Engineers) can specify materials that reduce the use of natural resources such as sand and aggregates. In instances where non-structural concrete or aggregates need to be used, recyclable and reusable construction materials should be selected wherever possible. For instance, alternatives such as recycled crushed concrete can be used as hard-core in road or pavement instead of using new stones.
Other prefabricated nonconcrete components such as glass facades, cladding, metal parapets, and prefabricated bathroom units are good choices of sustainable products. Drywall partition system is also a good alternative as it consists of stud frames and plaster/cement boards all consume little sand.
Steel is an excellent reusable material. Independent agencies (and some steel producers) around the world have performed life-cycle analysis on the environmental impacts of using steel. Based on the results, informed designers can confidently specify steel products in their various forms for projects of all sizes, from single storey, low rise to high rise buildings.
Construction using sustainable materials offers many benefits throughout the various stages of a building’s life cycle.
Recycling of Waste Materials
To enhance sustainability in the construction industry, wastes can be turned into resources to reduce disposal problems. A few types of waste are being studied, such as incinerator ashes from domestic refuse, spent copper slag fines which are residue from sand blasting and waste concrete from construction, renovation and demolition (CRD) of old buildings.
CRD Waste: Concrete from construction, renovation and demolition (CRD) of old buildings can be recycled. However, there is difficulty in separating the stone, known as aggregate, from the cement for reuse in new structural concrete components. The cement-coated old concrete may weaken the new concrete if it is not treated properly. There are new technologies around the world to separate the old cement from the waste concrete. The local researchers are currently conducting studies for local usage. Nevertheless, the use of waste concrete for non-structural concrete components such as partition walls, road kerbs, paving blocks are possible. Such application has been proven to be efficient and economical.
Incinerator Ash: An unique challenge due to our limited land area and high rate of waste generation, Municipal Solid Waste (MSW) is generated every day and the waste is disposed of by incineration. Incinerator ash or the MSW ash is the residual from the combustion of domestic waste. It is expected to have a variety of chemical species, some of which may pose environmental problems if it is not disposed of properly. A project is being carried out to recycle the ash into an aggregate product using a patented technology which has been used in various countries including the United States, Taiwan and Bermuda. The technology for processing the ash involved proprietary systems to remove ferrous and non-ferrous metals, screening, removing unburned materials, and treatment to mobilise certain heavy metals. The aggregate product has been tested to be non-hazardous and is safe for use. It has been used in diverse applications such as trench and backfill, shore protection, land reclamation, concrete block, base and sub-base for road construction.
Future Research Agenda
It may be useful to consider this in two overlapping parts based on the type of building technology to which it relates.
Conventional building technology, based on bulky, common, cheap materials has led to initiatives in waste reduction, recycling, regulatory control and conventional life cycle assessment based on a building life of 50 to 100 years. Sustaina-bility is largely seen as a question of balance between what can be extracted with minimal environmental impact and demand. It is assumed that these can be readily agreed and quantified and the relevant sums done. Design for deconstruction (DFD) to facilitate recycling is based on reducing the quantity of virgin raw materials needed to be extracted and used or in reducing the need for landfill disposal.
New building technology, based on the use of fewer materials in a more sophisticated or ‘clever’ manner (Less is More) points in a somewhat different direction. Assessment of sustainability may focus on what is covered in assessment schemes rather than attempting to standardise and agree a fixed methodology. Life cycle assessment may be based on a much wider range of building lifetimes, from very short (accompanied by total recycling/reuse/renewability) to very long (where environmental impacts are ‘written off’ over the long life of the building). The focus of attention may shift to relatively small quantities of key resources or materials which play an important role in modem sustainable building. These might include the alloying agents in steel rather than iron ore and limestone, rare metals such as titanium and indium which may come from very environmentally sensitive areas (eg. beach sands) or because they are rare, generate an inordinate amount of waste in their production. These rare elements may play a critical role in the development of ecologically sustainable building and DFD will be based on the recovery of small quantities of critically important materials. They may become politically strategic further complicating issues of equity.
The issues of equity in the social and socio-economic aspects of sustainability, both within and between countries, will become more critical as populations continue to increase and demand higher material standards of living.
The ability of this planet to maintain an environmental equilibrium has been disturbed, perhaps irreversibly. Population expansion and the corresponding increase in consumption on one hand and the reduction in the carbon storage capacity through deforestation on the other pose the most critical threat. The construction industry is the major contributor to the environmental loading on the earth and needs to respond to by substantially improving efficiency and effectiveness of in its entire production process. However, with an inevitable increase in population and demand for buildings and infrastructure services, even a dramatic improvement in environmental management of the construction industry is unlikely to offset an overall rise in the environmental loading caused by the increased level of building activity. If the scientists are correct in warning that the carrying capacity of the earth has already been disturbed, then the major challenge will be to minimise the rate of consumption increase and match it with a corresponding improvement in environmental efficiency and effectiveness associated with human activities.
How this is achieved will differ according to circumstances. The development of life cycle assessment techniques and their role in the assessment of sustainable construction will continue to be crucial. As building technologies develop further the key elements of sustainability may change and researchers need to be aware of such developments.