The construction is an office building originally in masonry whose renovation has been designed by atelier d’architecture Rivat as architectural firm (Architecte associé: atelier des vergers).
The renovation has been completed in 2017 and it is located in the Rhône-Alpes region, and precisely in the suburbs of the town of Saint Etienne, near the hill of Villebeouf in a wooded area.
The treated floor area accounts for 4332m2 according to PHPP. The solution sets are based on external insulation, that allows to modernize the building characterized by the typical architectural aspect of the1960s. Moreover, the wooden cladded boxes that overhang from the existing façade, offer a significant improvement of the internal atmosphere of the offices, providing new points of view for the surrounding landscape.
In addition, the installation of 7 geothermal boreholes, of around 100 m depth, allows to provide an effective support for both reducing heating loads during the winter season and, on the other hand, the cooling loads during summer.
The geothermal boreholes are coupled with the automatic night ventilation in summer and allow to store in inertial partitions a freshness which will be restored over several hours during the day. In addition, a geo-cooling battery is installed for the supply to offices and meeting rooms, benefiting from the freshness of the earth brought by the boreholes, and it offers cooling by the air during the day, via the air vents installed in each room. The comfort in summer is also ensure thanks to the external automated shading system, reducing effectively the solar gains.
In particular, the external wall, originally in masonry, is insulated with 18 cm of polystyrene panels and presents a thermal transmittance of 0.162 W/(m2 K) after the renovation, while the roof is insulated with 24 cm of XPS and has a U-value of 0.089 W/(m2 K). The windows has a wooden frame with 1.4 W/(m2 K) of thermal transmittance and high thermal performance glasses with U-value accounting for 0.86 W/(m2 K).
The heating is supplied by low temperature gas boiler, while the domestic hot water is produced by an additional electric water heater.
Moreover, the building is equipped with a 307 m2 of photovoltaic system installed on the roof.
The overall performances are significantly below the requirements for having the Passivhaus certification, and in particular the Primary Energy (including heating installation, domestic hot water, household electricity and auxiliary electricity calculated according to PHPP) accounts for 73 kWh/(m2 a), with a limit value of 121 kWh/(m2 a).