"The aim of the Performer project is to devise a holistic (total lifecycle,multi-aspects, context-based) building energy monitoring methodology that factors in appropriate energy performance indicators, information models, and simulation tools, to achieve building energy performance targets. The project energy performance simulation and monitoring aspects will rely on an ICT infrastructure that will re-use, adapt, and further develop a number of open source ad commercial technological blocks, including (i) an ""Energy instrumentation kit in a box"", (ii) an Energy Simulation Environment, and (iii) a building legacy and monitored data storage and computing infrastructure. The holistic building energy monitoring methodology will be tested and validated in the context of four selected demonstration projects in France, UK (Wales), Spain and Poland, articulating common attributes aswell as general and unique features with a view of ensuring scalability and EU wide application. The project will devise a building-oriented and ""large scale"" energy performance strategy aimed at large clients with extensive building stocks with a view of achieving economies of scale leading to sizeable retrofitting cost savings and reduced pay-back periods. It will also deliver knowledge transfer and embedding related activities, via the elaboration of a PERFORMER replication guide, to ensure results uptake by industry across Europe."