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The renovation of Doragno Castle - Rovio, Switzerland

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Credits: L. Carugo

The building is used as a residential, and the aim of the renovation has been the conservation of the ancient walls of the medieval castle, considering modern comfort standards with the target of achieving a building ad a high standard of energy efficiency, (i.e. the NZEB standard).


The castle of Doragno was born from the transformation of an ancient medieval castle into a private residence where the existing building, which did not enhance the castle, has been subsequently restored, giving a new breath to the ancient walls of the building, and completed with a new zero-energy building (NZEB) also using renewable solar energy in an integrated roof solution. The original stone walls are highlighted by large windows that complete the volume of the existing building. An integrated photovoltaic system and solar collectors are installed on the roof.


In this project it was chosen to preserve only the medieval part of the building. This choice was made because the interventions done in the sixties do not help to preserve the history of the castle and where even hiding some medieval parts. The cultural heritage office supervisors approved the project and agreed with reflections and considerations from architects. In this project the architects have re-created the shape of the castle using modern materials that differ from the original ones but do not dominate and discretely approach to ancient parts.


The building was restored preserving the walls and completing the volume with new materials that with the aim not to drown out the old part of the building, but to enhance it. The construction consists of two main buildings, one to the west that includes a basement and 2 floors above ground and one to the east that includes 3 floors above ground.


The restoration project started from the right premise of completing what remained of the walls of the tower to return the shape so that in the surrounding landscape the building of the past once again became legible. In this project we have re-created the shape of the castle using modern materials that differ from the original ones but don't dominate and discretely approach to ancient parts. Moreover, the existing walls has been insulated with an internal layer allowing to reach the target 0.24 W/m2 K from an initial value of 0.9 W/m2 K. Also the roof has been renovated and insulated from a thermal transmittance of 1 W/m2 K towards 0.2 W/m2 K and renewables have been installed. In particular, solar thermal collectors has been integrated in the south-east roof pitch for the production of DHW domestic hot water and for heating and photovoltaic system integrated in the south-east and south-west slopes of the roofs. The selection of roofing materials allows the integration of solar systems in order to make a uniform surface, that consider the aesthetic characteristics of the solar thermal panels and their geometry and position in the roof. Solar thermal and PV modules are coplanar to the roof and the similar aspect to solar photovoltaics panels in order to minimize their visibility from the surrounding environment.


The new heating system consists of a reversible air-water heat pump powered by the photovoltaic system on the roof. The thermal energy produced that is used to heat, cool and produce domestic hot water becoming completely free and renewable. Distribution is made both from radiating floors and fans. The raised floor is composed of two functional layers, one load-bearing and the other thermally active: the lower layer, thermo-active, consists of radiant panels of the reversible heating and cooling system. Being a new system, which integrates into the newly constructed building, it does not compromise the existing castle building, there are no compatibility and conservation problems.


The overall consumption assessed through the local energy labelling approach accounts for around 45 kWh/m2, including the need for heating and domestic hot water production.

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