Energy use in buildings accounts for approximately 40% of EU energy consumption. Due to this high energy use, one of the three main targets proposed by the European Economy Recovery Plan in 2008 is "to encourage Energy-efficient buildings, to promote green technologies and to develop energy efficient systems and materials in new and renovated buildings with a view to reducing radically their energy consumption and CO2 emissions".
In order to achieve these objectives, drastic measures are required. The improvement of energy efficiency of conventional generation technologies is not sufficient and a high proportion of energy demand supplied by renewable energy sources is essential. Taking into consideration that heat demand can represent up to 60-70% of total amount of energy consumption in a residential building, heating system based on Seasonal Thermal Energy Storage (STES) concept is currently the most promising technology able to fulfil the objectives established in Europe about energy efficiency in a short term. The fact that the concepts developed within this project are based on innovative adaptation of existing technology is a remarkable aspect, as it makes possible the development of nearly zero energy buildings (one of the objectives of EPBD directive) at short time.