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Smart City project SINFONIA: the renovation of the housing complex of Bolzano – via Passeggiata dei Castani

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Credits: Municipality of Bolzano

The renovation of the residential complex of Via Passeggiata dei Castani is one of the interventions developed within the FP7 Smart City project SINFONIA and has been concluded at the beginning of 2019.


The area is located in the east side of the city of Bolzano, under a mountain and the complex has been build in the ‘90ies. The complex is owned by the Municipality of Bolzano and it is composed by two buildings, that have 72 apartments distributed by four staircases for a total surface of 7456 m2.

The existing building presented concrete structure and the external walls are made by with hollow bricks and with an air cavity insulated with a layer of polystyrene (of around 4 cm) that was also found in the roof. The windows were double-glazing with aluminum frame, and presented a thermal transmittance of around 3.1 W/(m2 K).

Despite the building was quite new, it presents a significant problem of condensation in the walls (and level of humidity was quite high), due to the non-continuous insulation and the large amount of thermal bridges. Therefore, the façade presented clear signs of condensation and mold problems, especially in correspondence of thermal bridges.


The energy concept of the intervention is based on the envelope renovation in order to improve the energy efficiency and avoiding the condensation risk and infiltration in the basement. The chosen technology was a prefabricated timber façade, insulated with 25 cm of fiber glass (with a final U-value of 0.15 W/(m2 K). The façade elements arrived on the building site with high performance windows, with triple glazing and a frame of wooden and aluminum, already installed. The façade elements have been anchored to the existing structure through a reinforced steel support, allowing for an easy installation.


Concerning the heating system, the existing decentralized boilers have been changed with a centralized heat pump supplied by sixteen geothermal sources. The intervention foresaw to keep the initial distribution system in the apartments, thus the heat pump is integrated with the existing radiators, while the distribution system has been insulated. A significant amount of renewables has been installed, and in particular: a solar thermal field in the roof top of around 440 m2 and a photovoltaic system with a 52 kWp of power.


One of the goals of the renovation was to enable the tenants to remain in their flats during the interventions, thus the main challenge of the design dealt with the organization of the works, and the integration of the new technical spaces, that have been placed in external cavities integrated in the new façade.

The final ideal energy after renovation demand accounts for less than 30 kWh/(m2 year), while the overall Co2 emissions are foreseen to be lower than 10 kWh/(m2 year), thanks to the 76% covered by the renewables installed.


If you want to read more about this case, visit the website SINFONIA project and the website of Agenzia Casaclima that, with the local designers and Eurac Research, supported the Municipality of Bolzano in the renovation process.

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