Energy efficiency has gained more and more importance in the past years because climate change is one of the most urgent problems worldwide.

Our environment is damaged by the emission of greenhouse gases such as CO2. In order to reduce the amount of greenhouse gases emitted into the atmosphere, energy efficiency has to be increased.

Given that it is necessary to use energy and that renewable energy sources by far cannot cover the global and ever increasing demand of energy

	the only alternative is to use energy as efficiently as possible.

In the last years, energy efficiency targets have been developed within the frame of the Kyoto Protocol or EU directives such as

	»   the ESD (Energy End-use Efficiency and Energy Service Directive) and   »   the EPBD (Energy Performance in Buildings Directive).

Additionally, norms have been introduced and legislative measures initiated on national level in order to tackle the climate change problem via improving the use of energy.

Furthermore, energy dependence could be reduced. On the one hand, the dependence on non renewable energy sources which supply the world could be secured for the coming years, and on the other hand, the dependence of energy supply by other countries which are the owners of these energy sources.