The overall objective of MESSIB is the development, evaluation and demonstration of an affordable multi-source energy storage system (MESS) integrated in building, based on new materials, technologies and control systems, for significant reduction of its energy consumption and active management of the building energy demand. This new concept will reduce and manage smartly the electrical energy required from the grid favouring the wider use of renewable energy sources . It will reduce raw material use for thermal performance and improve the indoor environment, the quality and security of energy supply at building and district level, including Cultural Heritage buildings. Furthermore, a significant reduction of the energy unit cost for end-users will be achieved. MESS is composed by two thermal and two electrical storage systems, integrated with the building installations and a control system to manage the building energy demand. The MESSIB basic principles are: 1.Rational use of thermal energy for primary energy savings and for increasing the indoor comfort. 2.Improvement of electrical energy storage in combination with RES to shift the demand with the production and to optimise the use of low cost “off peak” power from the grid. 3.Integration of the technologies in the building. Each of the technologies developed in the project will be integrated with conventional installations optimizing their functionality. 4.An active control system will manage the profile of use of each storage system and their interactions. This will contribute to the intelligent management of building energy demand and to ensure its security, quality and reliability.