Large energy demand from the existing, underperforming Building Stock (BS), including refurbished and recent buildings jeopardizes the effort to reach deep decarbonization target. Such BS provides poor occupants’ comfort and suboptimal use of energy. RePUP develops, assesses, and implements a modular and reliable solution for bridging the performance gap of the existing BS related to both the BROKEN OCCUPANTS’ EXPECTATIONS and the OVERPRODUCTION OF CO2 emissions caused by an INTENSE AND POORLY CONTROLLED USE OF ENERGY. RePUP ground-braking human-in-the-loop (HuiL) approach is applicable to many types of buildings with different insulation levels, thermal mass and building service systems. RePUP includes: 1. DEBUG-AI to detect and eliminate faults. 2. HuiL perception-based control through a dedicated feedback and occupants’ tracing app: 3. A 3D (weather, energy prices, dynamic occupants’ needs) model predictive control to maximise the renewable energy use (flexibility), under the RePUP COMFORT GUARANTEE. The RePUP solution will be developed and tested in demo-buildings (offices, campus buildings, schools, private houses). RePUP will create growth and exporting opportunities for the Danish IoT and HVAC-related industries and SMEs, by generating a ready-to-be-implemented solution. This will be commercialised by CLIMIFY Aps and the consortium partners. RePUP will allow Danish key players to set future standards for buildings, IoT, HVAC, and Indoor Environmental Quality.