With regards to construction materials, adoption of sustainable selection criteria would imply the following: Matter and energy consumption should be minimized Minimum level of human satisfaction should be maintained. There should be minimum negative environmental effects. Any effort to minimize the consumption of matter and energy has to target minimizing entropy gain and intergenerational of equity objectives. It has to be kept in mind that the process of consumption increases the entropy of materials and energy making them unsuaitable for use in the future (Roberts, 1994; Rees, 1990).
The basic tenet of sustainability and sustainable material selection would therefore be maximizing utilization and minimizing consumption of matter and energy. In laymen’s language this translates into ‘doing more with less’. Doing more with less however has to be balanced with maximizing human satisfaction with the less of matter and energy that is being consumed in the process. Unless the satisfaction of people is achieved, sustainability would run into a dead end. People and users will not accept changes necessary to make the world a better place to live in unless they are satisfied by the results of those measures.
Ensuring the satisfaction of people therefore becomes an integral part of sustainability. A part that is closely connected with economics as, in our economy-driven society, people are satisfied only when there is assurance that their economic interests will not only be safeguarded but also enhanced appreciably. Minimization of costs, maximization of comfort and safety and edification of the human spirit should be the ideal objectives in the process of selection of construction materials (Day, 1990).
It all boils down to the sustainability of the human race which in turn makes it essential to ensure the sustainability and preservation of the ecosystem. The sustainability of the ecosystem is ensured when emphasis is put on maintaining biodiversity, species habitat is left undisturbed and environmental deterioration and pollution are brought under control. The design objective of any DSS for selection of construction materials on the basis of sustainability will thus have to make these three global presumptions – less consumption of energy and matter, high human satisfaction and minimal negative effect on the environment.
A set of metrics of sustainability based on the definition of sustainability has to be developed for the construction materials. The metrics would then have to be adapted into an approach for comparing alternative materials to help in the selection process. Classification of Sustainability Attributes The next step in designing a Decision Support System for sustainable selection of construction materials would be take the attributes of sustainability and develop a system or taxonomy for classifying them into the categories of technology, ecology, economics and ethics.
Since technology is utilized to build construction facilities, it is imperative that sustainable technologies are applied. Carpenter (1994) defines sustainable technologies as technologies that do not harm the environment in any way and are based on the concept of renewing, reusing and recycling materials. Materials have to contribute to sustainability by building up suitable technologies. For a specific use, the measure of a material’s adaptability to sustainable technology is obtained by the extent to which the material is able to meet the required technical performance.
Span, reliability, ability to recycle and resistance to decay and damage are other technology-related indicators. Ecological sustainability can be achieved through material selection if the objective of material selection is to minimize environmental damage and degradation over the entire lifecycle of the material right from the stage in which the raw material is extracted to the final stage of either disposing the material or adopting it for reuse through the process of recycling.
Of particular importance in the consideration of sustainability is the way the material will affect the ecology. The domain of all human activities comprises the natural ecological systems which provide all the raw materials to meet the varied requirements of human beings (Norton 1994). Thus, integrity of the systems has to be maintained in order to ensure the continues availability of raw materials in the form of ecological resources. The search of feasible alternatives for limited natural resources leads us to the realm of economic sustainability.
Alternative resources that can be developed at minimal cost to the society have to be maintained and identified by the Decision Support System. The total life cycle cost of a project depends on the life cycle costs of the constituent construction materials. Selection of construction materials based on the lowest life cycle cost ultimately brings down the life cycle cost of the entire construction project. Manufacturing, transportation, assembly, maintenance and disposal or recycling costs determine the lifecycle cost of a construction material.
These lifecycle costs in turn determine the economic sustainability of a construction material. The moot point of sustainability is adopting a futuristic view. The concern is not only with meeting the needs of the present generation but at the same time ensuring that resource utilization is done in such a way that it is possible to retain, invest and convert them in such a way that there is no scarcity to meet the requirements of the future generations (Daly & Cobb 1994). This is the principle behind the ethics of sustainability.
The attributes of ethical sustainability are the extent of depletion of natural resources that utilization of the material could represent, extent to use the material can be reused and to which nonrenewable resources the material can be used as a substitute (Norton, 1994). The Decision Support System therefore has to base its classification of sustainability attributes on the taxonomy of technology utilized, maintenance of ecological balance, economic feasibility and ethical concerns for the future of human kind. The vast scope and complexity of such a DSS can be appreciated when we take all these factors into consideration.