The gradual shift of the global energy system towards electricity will be fundamental for the decarbonisation process and particular attention will be paid to interventions on existing buildings.With the technology of WLHP (Water-Loop Heat Pump) air conditioning systems, the primary heat pump (HP) will produce water at a temperature and with a flow rate compatible with poorly or not insulated pipes and with diameters and distributions typical of common radiators (for example from 20 to 35 °C both in winter and in summer).The existing generally high temperature terminals are replaced with extremely silent WLHP water/air heat pumps. The distribution (Water Loop) will be maintained at a neutral temperature by a primary heat pump (first stage), while the new terminals, still in heat pump, will provide for hot and cold air conditioning of the environment (second stage).The piping system of the existing plant can be fully reused, thus avoiding invasive interventions and allowing housing continuity during the works.