ICT is recognized as being a key player against climate change: pervasive sensors and actuators can efficiently control the whole energy chain (Smart Thermal/Electricity Grid). On the other side, advances on 3D modeling, visualization and interaction technologies enable user profiling and real-time feedback to promote energy efficient behaviors. To unlock the potentiality of these technologies, the DIMMER projectfocuses on:-\tInteroperability of district energy production/consumption, environmental conditions and user feedback data;-\tExploitation of effective visual and web-based interfaces to provide pervasive and real-time feedback about energy impact of user behaviors;-\tIntegration of Building Information Models (BIM) with real-time data and their extension at the district level (DIM);-\tNew business models for energy traders and prosumers exploiting user energy profiling.The DIMMER system integrates BIM and district level 3D models with real-time data from sensors and user feedback to analyze and correlate buildings utilization and provide real-time feedback about energy-related behaviors. It allows open access with personal devices and Augmented Reality (A/R) visualization of energy-related information to client applications for energy and cost-analysis, tariff planning and evaluation, failure identification and maintenance, energy information sharing. All the following technologies are included: Real-time data collection; Advanced middleware technology for data integration; Simulation and virtual visualization; User/social profiling, visualization and feedback; Energy efficiency and cost analysis engine; Web interface and interaction.In order to validate the DIMMER innovative system, both public (university campuses, schools) and private buildings included in mixed-up (mixité) urban districts are considered in two different cities, in the North and South Europe, Turin (IT) and Manchester (UK). As most energy usage of buildings throughout their life cycle is during the operational stage (~80%), the project gives special attention to existing and historical buildings.In conclusion, the expected results are a consistent reduction in both energy consume and CO2 emissions by enabling a more efficient energy distribution policies, according to the real characteristics of district buildings and inhabitants as well as a more efficient utilization and maintenance of the energy distribution network, based on social behavior and users attitudes and demand.