The global deep decarbonization target is jeopardized due to a large energy demand from underperforming buildings. This includes both refurbished and recent building stock. Such buildings provide poor occupants’ comfort and suboptimal use of energy. In the RePUP (Real-time Performance UPgrade of buildings) project we develop, assess and implement a modular and reliable real-time management solution for bridging the performance gap of the existing buildings. This gap is related to both broken occupant´s expectations as well as overproduction of CO2 emissions, caused by an intense and poorly controlled use of energy. The ground-breaking human-in-the-loop (HuiL) approach from RePUP is applicable to many types of buildings with different insulation levels, thermal mass and building service systems. A consortium of nine partners (see RePUP goals) from companies and academia is contributing to the research and development with their complimentary expertise.