In European countries, buildings are the major energy consumers due to the general low energy performance of the existing building stock. To achieve the ambitioned targets for emissions reduction, it will be necessary to take actions for its large scale renovation. However, today's standards are mainly focused on new buildings, guiding the improvement of the energy performance of the existing buildings into expensive processes and complex procedures that seldom are accepted by users, owners or promoters.

A new analysis framework is developed and applied to assess the benefits of building energy efficiency policies and programs. One of the main advantages of the new energy productivity analysis is that it accounts for both economic and energy performances of energy efficiency actions using only one metric. Specifically, the approach applies the concept of energy productivity to the building sector and accounts for both value added and energy savings of energy efficiency measures.

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 German government has developed a variety of policy instruments intended to reduce national CO2 emissions. These instruments include a programme administered by KfW bank, which aims at improving the energy efficiency of buildings. It provides attractive credit conditions or subsidies to finance refurbishment measures which improve the energy efficiency of buildings significantly. The refurbishment programme leads to a reduction in energy use, which benefits private investors by reducing their energy bills.

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.