Building with centralized hybrid system, Milan
Refurbishment in climate zone E* with heating, air conditioning and hot water system

Located in the centre of Milan, the 1960s building consists of 53 flats covering a total of 6500 m2. The building had undergone an initial complete renovation in 2000, which also involved the building envelope. Heating was provided by two traditional boilers for heating and domestic hot water and two chillers for summer cooling. The distribution of heat and cold was done with radiators and fan coils, respectively.
Requirement: In 2023, it was decided to improve the building’s energy performance by intervening on the air conditioning system, but with the need to maintain the present distribution system.
*The climate zone E in Italy is that which has a level of 2102 to 2999 heating degree days (HDD). It is located in the northern parts of Italy, along the Apennine Mountains and in the very center of inland Sicily. (source) According to Köppen-Geiger it lies in the Cfa zone.
Lessons learned
- The heat pump system has proved to be an excellent solution for improving the building’s energy efficiency, even in combination with a building envelope that is not particularly performing and maintaining the old heating and cooling distribution system.
Key facts
Building | Heat Pump and Source | ||
Location | Milan, Italy | Number of HP | 2 (heat) + 1(cooling) |
Construction | 1960 | Installed power | 352kW (2x 93kW + 1x 186kW) |
Refurbishment | 2024 | Operation mode | hybrid |
Heat distribution | radiators | Heat source | ambient air |
Heated area | 6500 m² | Type of system | Central |
No. of apartments | 53 | Model | Sheen EVO 2.0 Magnum WSAT-XEM chiller |
level of insulation | medium thermal | ||
Heating sytem | Domestic Hot Water | ||
Heat demand | – kWh / (m²a) | DHW demand | – kWh / (m²a) |
Heating temperature | 58°C | Max. temperature | 55°C |
Additional heating | Gas boiler 390kW | Circulation system | – |
Type | centralized system | ||
Other information | |||
PV installed | – | COP | – |
Refrigerant | R32 | ||

Description of the technical concept
The two existing boilers were replaced with 2 high-efficiency heat pumps with inverter technology and ecological refrigerant R32 Sheen EVO 2.0 and 2 condensing boilers of 200 kW, which are used as back-up and integration in situations where high temperature water is required. The heat pumps can also be used as a back-up to the chiller in peak cooling demand.
To replace the 2 old chillers, a high-efficiency chiller with Magnum WSAT-XEM inverter technology was installed.
The entire system is managed by Clivet’s INTELLIPLANT Building Management System, which coordinates the entire heating and cooling plant, activating the plant resources according to the requests received from the individual flats and always activating the most efficient resource, has made it possible to operate the heat pumps in conjunction with the boilers, thus providing a perfectly reliable and efficient hybrid system. Intelliplant also makes it possible to maximise the total efficiency of the system by making the units work at their maximum efficiency and allows the customer to monitor thermal, cooling and electrical consumption.
The system allows for constant monitoring and therefore prompt intervention at any time or in the event of faults or failure.
IT007 Centralized Hybrid System