| Executive summary
The pursuit of sustainable development brings the built environment and the construction industry into sharp relief. This sector of society is of such vital innate importance that most other industrial activities in the world simply fade in comparison. In every country in the world, the built environment normally constitutes more than half of total national capital investment, and construction represents as much as 10% of GNP.
Precise statistics about the size and importance of this sector do not really exist, but it is widely recognised today, with its estimated 111 million employees, as being the world's largest industrial employer, accounting for approximately 28% of all industrial employment.
In many developed countries it accounts forup to half of all the raw materials taken out of the earth's crust by weight, as well as producing a considerable waste stream, although fortunately a significant and growing proportion of this is recycled. For the most part, construction activities contribute positively to sustainable development. In addition to providing significant opportunities for employment worldwide, one of its fundamental roles is to maintain and improve the quality of the built environment which in turn significantly influences the quality of life of citizens. In fact it is no exaggeration to say that this industry perceives its role as being responsible for continuously improving mankind's physical living conditions.That above all, is its most valuable and enduring contribution to ¡®su stainable development'.
It also accepts that some types of construction projects are controversial, be they new roads in beautiful countryside or the construction of dams in the developing world. But it is not the industry that decides what gets built and where.These are matters for local communities and society at large to determine. Once such decisions are taken - and compromises often have to be struck - contractors share the responsibility together with local authorities, designers and consulting engineers to ensure that projects are built in such a way as to minimise environmental impacts. Broadly speaking, this process is what has come to be known as ¡®sustainable constructio n'.
In Europe, the built environment accounts for about 40% of energy use rising to as much as 50% in some countries if construction activities (including materials production and transport) are also taken into account.This implies that the built environment (transport in the United States) is the largest single contributor to greenhouse gas emissions.This presents the construction industry with both a challenge and an oppo rtunity.
Significant possibilities exist to reduce
emissions from buildings through increased energy-efficiency measures, and in the longer term through the exploitation of renewable energy resources. Many of these technologies already exist, the real challenge lies in convincing owners of existing buildings to undertake the necessary rehabilitation works. Much will also depend on technological advances aimed at reducing the relative costs of rene wables.
Renovation and maintenance (R&M) works now constitute an ever-growing share of construction markets, especially in the developed economies. Sustainability infers that demolition has now become the last choice in preference to renovating existing structures whenever feasible. R&M in Europe now represents about one third of all construction activities and in some cou ntries is estimated to ¡ | 
