The project concerns the energy upgrading of the building of the Primary School of Ormylia, the municipality of Polygyros. The building currently exhibits reduced thermal comfort conditions throughout its operation and increased energy consumption resulting in its classification in category E of the Buildings Regulation (KENAK). The project includes interventions in the building’s shell (face and roof thermal insulation, change of frames), modification of the building’s heating installation (application of a hybrid system with boiler and air-water heat pump), replacement of boiler, installation of photovoltaic system and interconnection with PPC for energy net metering, replacement of luminaires and installation of automatic heating control system. Upon completion of the interventions, the building is expected to be energetic in category A of KENAK.