All member states of the European Union are bound to decrease their greenhouse gas emissions. For example, the EU climate and energy package requires member states to improve their energy efficiency by 20%, increase -renewable energy production by 20% and reduce their emissions by 20%. With about 40% of CO2 emissions heating, cooling and hot water production in buildings is one of the largest greenhouse gas producers. At the same time the building sector has the largest potential for energy savings. In their effort to lead a change towards greater energy efficiency and a reduction of greenhouse gas, many companies, cities and municipalities are in the process of developing low carbon action plans. However, the costs for developing optimal action plans and their continuous monitoring and op