After 15 M € of works, Arte Charpentier Architects (agent), with NM Architects and Art & Fact Architects, delivered in Dijon (Côte-d’Or) in June 2021 the transformation of the Mercure tower into a Sigma tower (9,600 m² offices). Company press release.
The Mercure tower has definitely given way to the Sigma tower. In mid-June, teams from Bouygues Bâtiment Nord-Est and Linkcity Nord-Est handed over the keys to a building completely transformed by more than two years of work.
With its eleven floors marking the western entrance to the city and adjoining Dijon train station, the Mercure tower has always counted, since its design by Henri Favre in the early 1970s, among the city’s emblematic works. Asphalt, energy-intensive and classified as a high-rise building, the building is considered, 40 years later, as outdated and too expensive to operate.
While the hypothesis of demolition is quickly ruled out, how can we give a second life to these 10,000 m² of offices combining both technical and legal constraints?
After a first site visit in 2014 and a few months of analyzes, the teams from Linkcity Nord-Est, a real estate development subsidiary of Bouygues Bâtiment Nord-Est, embarked on the project. It all starts with the necessary control of the 15 property lots. Although convinced of the merits of the approach, the owners and occupants had their own constraints, which of course had to be taken into account. The signing of all the promises to sell came a year later, followed by the obtaining of the building permit in February 2016.
The project imagined by Arte Charpentier, architect mandated by a consortium made up of NM Architects and Art & Fact, won the support of the city. It provides for the neutralization of two floors, activating the declassification of the IGH. In order to let in light and remove asbestos, the building will also have to be stripped of all its facades to replace them with more transparent and contemporary ones.
Outside, as inside, the restructuring should give the building a tertiary identity, energy performance and quality of use at the level of a new building. All with minimized operating costs to align with the local market.
In February 2019, Bouygues Bâtiment Nord-Est began work on the Sigma tower with a first nine-month phase which will allow the renovation of the “Patio” (R + 2 building adjoining the tower). The second phase will concern the tower itself and the renovation of its 6,600m² over a period of 15 months. The site will have to undergo a three-month interruption due to confinement.
The interventions begin with a cleaning step where the concrete structure is completely exposed. As such, the 3,000 m² of carpet removed are upgraded in partnership with the Emmaüs Norges association, ie 12 tonnes of waste avoided.
To remove the imposing concrete thorns and facade elements, a crane is installed on the roof. The high slabs of the two upper floors were demolished in line with the gables to create vegetated terraces. The insulation from the outside then the installation of the curtain wall, cladding, glazing and mesh mark the end of the shell.
The windows of the large facades are in wood and the curtain walls are in lacquered aluminum, with solar control on the south facade for better comfort. As the building is out of water and out of air, the interior trades are activated.
The Sigma tower now meets the criteria for Breeam New Construction level Good and BBC Rénovation certifications. They guarantee energy performance and a quality of the working environment that is fully in line with today’s expectations. While the Patio section has been occupied since the end of 2019, the tower is preparing to welcome I-BP (the IT subsidiary of the Banque Populaire) and its 300 highly qualified employees in the digital sector.
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