Comune di Milano,

Lorenzo Pagliano

+39 02 2399 3870


Milano, the second-largest city in Italy and the capital of Lombardy has a population of about 1.35 million people. The citys urban area is the 5th largest in the EU and the largest in Italy with an estimated population of about 5.2 million. As the main industrial, commercial and financial center of Italy, it has a metropolitan region that contains a population of over 8 million people.

The building after refurbishment
Solar panels on the roof of the building
1st phase of refurbishment

The district and the building stock

Zona 4 is one of the 9 administrative districts of Milano, located at the Southeast border. With a surface of about 21 km2, and a population of 152 300 inhabitants, its density is in line with the average density in Milano, about 7250 inhabitants/km2. The design and implementation of the activities in Zona 4 foreseen in EU-GUGLE is a perfect case for devising, testing and fine-tuning innovative solutions to be replicated at the scale of the entire city.

  • Surface:  21 km2
  • Population: 152 300 inhabitants, 7 250 inhabitants/km2.
  • Surface to be renovated (total gross floor area): about 18,000 m²
  • Type of buildings: public residential buildings (social housing), and one public school (kindergarten).
  • Primary energy savings target: up to 82%.

Targeted energy savings Milano: 82%


For all the renovations carried out in the buildings in Milan, the action plan was defined in three steps, according to the logical order suggested by the Physics.

  1. Improve the quality of the envelope first, thus reducing the energy demand of the building, and at the same time reaching higher levels of indoor comfort;
  2. then work on the mechanical systems, in order to improve their efficiency;
  3. finally, use as much energy from renewable sources as possible to satisfy the energy demand of the building, after having reduced it in the previous two steps.

This approach would allow to obtain the optimal results in terms of energy savings, environmental impact and economic costs during the service life of the building; then it would be possible to have a first collection of successful cases (documented and unequivocal) for a certain climate and context, and also to create a large and stable market with important volumes of activity for all the construction actors and building aspects (envelope, mechanical systems, renewables).


Fulfilled renovation measures

Via Feltrinelli 16, residential building

The original building showed a low performance envelope and poor quality building systems, resulting in a low quality environment for occupants. The retrofit work on Feltrinelli 16 has been focused on improving the quality of the envelope. Savings obtained by the envelope retrofit are complemented by savings due to heat recovery on exhaust air and PV system designed and installed during the course of 2016. A great attention has been paid both by researchers of Politecnico di Milano and by the technical staff of the Municipality in order to enhance the energy performance of the envelope of Feltrinelli 16, for example checking insulation strategies, identifying and correcting thermal bridges, reviewing building systems control strategies and monitoring.

This extensive work led furthermore to the design and installation of an innovative heat recovery system on the exhaust air ducts (exhaust-air heat pump) and to the installation of photovoltaic panels on the roof of the construction.

Works were carried out in two phases:

  • 1st phase: thermal insulation works, from December 2010 to February 2014
  • 2nd phase: Exhaust air heat pump on the roof, from February 2016 to June 2016

Planned renovation measures

Via Feltrinelli 11, nursery

  • Retrofit of the building’s envelope (External walls, External windows, Roof and floor) by means of:
    • Decentralized mechanical ventilation system with heat recovery
    • Replacement of external glazing and frame with high performance components
    • External Motorized Solar protection system
    • Refurbishment of the roof (flat rather than pitched and with high insulation)
    • Improving the thermal resistance of floor (ceiling of the basement) by adding insulation layer
  • Passive cooling using controlled night natural ventilation
  • Building Management System:
    • Sensors for measurement
      • Sensors for Illuminance measurement
      • Sensors for CO2 measurement
      • Sensors for Temperature and Humidity measurements
    • Actuators for operation
      • Lights dimmer and on/off switches
      • Mechanical ventilations and heat recovery systems
      • Upper windows openings
      • External solar protections
      • Thermostat valve for heating system
  • Photovoltaic power plant
  • Connection to district heating network

Via San Bernardo 48-50, residential building

  • Within the flats:
    • Change of the external doors and windows.
    • Placement of shielding systems with packet curtains.
    • Placement of insect screens and anti-intrusion grids to allow a safe summer ventilation.
    • Doing over of gas lines and resizing of ventilation opening for cooking flames.
    • Change of the entrance doors with better performing ones.
    • Installation of temperature control valves on the radiators and of the calories counters on the zone valves.
    • Probes for collection of data about climate in every flat (T, UR and CO2).
  • Centralised mechanical ventilation system with heat recovery
  • No pipes and ducts visible on the facade
  • Centralized domestic hot water production system
  • Photovoltaic panels on the roof


Works in Via San Bernardo and at the nursery still have to be done. Works in Via Feltrinelli 16 are finished, so the results and impacts can be assessed. We are particularly proud of the result, attested by the energy certification, of the reduction of the primary energy demand for heating and domestic hot water of the building, from more than 250 kWh/(m2 year) to about 35 kWh/(m2 year). This was possible thanks to the accurate refurbishment of the envelope (walls and windows, correction of thermal bridges), which improved not only the energy performance of the building but also the thermal comfort in the indoor environments. The connection to district heating was also useful to reach the target value of the energy certification. The effects of the second phase of refurbishment are still being evaluated with the recently installed monitoring system.

We will monitor the following aspects (all the physical parameters will be monitored on hourly basis):

  • energy use for heating and domestic hot water of each apartment
  • indoor air conditions (temperature, relative humidity, CO2) in some apartments
  • photovoltaic production; monitoring of the exhaust-air heat pump system and of the central heating system (temperature of the fluids, water flow rates).

About impacts on the project area, EU-GUGLE is part of a group of projects running on the same area, with the aim to create the first smart district in Milan. These project put together a series of different actions, not only residential and public buildings renovation, but also public smart lighting, district heating, smart parking, electric mobility, especially applied to bike and car sharing, data collection (Urban Sharing Platform), smart governance (decision room/city lab), economic development and business (Smart City Lab).

Main challenges

In Italy, all public works are regulated by laws to prevent corruption and organized crime infiltrations. According to these laws, a lot of rules and procedures have to be followed. Hence, it’s not easy to respect the scheduling. In 2016, rules were made even stricter and procedures more complicated, and this is making the scheduling even more challenging.

For the renovation works in Via Feltrinelli 16, the specific challenges that have been encountered from the first phase can be summarized as:

  • Since works took place without the presence of the tenants in their houses, it was necessary to provide them an alternative recovery for the duration of works.
  • During the refurbishment works, the main problem was to work on an existing structure that was not flexible with respect to the creation on new spaces for mechanical systems.
  • Furthermore, the building construction company involved in the project did not always have much sensibility regarding the attention of construction details for the installation of insulating materials.