Over half of the population of the world live in
urban areas. This means that efforts to meet human
development goals and sustain economic growth
must be concentrated in cities. However, the pursuit
of more prosperous, inclusive and sustainable urban
development is complicated by climate change, which
multiplies existing environmental risks, undermines the
effectiveness of existing infrastructure, and creates new
resource constraints.
In this paper, we conclusively demonstrate that there

People spend most of their time inside buildings, and buildings are responsible for approximately one third of total direct and indirect energy-related worldwide carbon emissions. Likewise, buildings in the U.S. account for about 40% of total U.S. energy consumption. Future building development will be driven not only by emerging challenges such as vulnerability to a changing climate and resource scarcity, but also by disruptive innovations and societal changes.

The built environment accounts for approximately forty percent of the total energy consumption in developed countries. Because buildings have a long life, the greatest opportunity for energy reduction in the built environment will come from energy conservation in the existing building stock. An overview of the policy challenges presented by the built environment, with an emphasis on existing facilities, is accompanied by a discussion of specific technologies that may have the potential to reduce energy use.