Perhaps more than anything, what guided us in the design of this project, are the Erdre and the Loire, nearby, and their estuary winds, these winds with changing skies, loaded with gray, blue. It is this Nantes climate, unstable with constant variations, that the project invites in an active part.
Also determining the contact with the major structuring lines: exit boulevard, tram / train rail, which places the project in the urban rumor, which must be defended.
Lastly, the question posed by an open program which at the outset of the competition required, rather than an environmental guarantee obtained from an Excel spreadsheet, a reflection that unmistakably associates architecture and thermal performance, architecture and the evolution of uses, on the long term, in a sustainable perspective. This program is three entities associated in a dense form but still need to preserve their independence. Place of work and places of welcome dedicated to the grouping of the local agencies of Pole Employment, places of work and places of reception dedicated to the Pole of Nearness of Nantes Métropole, places of domestic stay for a quarantine of housing finally.
The tertiary building, the public face of this mix, is organized in a concentric way according to a series of rings arranged around the hollow and slender core of an atrium, constituting the place of reception of the public, but also one of the essential elements climate regulation of the building.
Place of a light breeze that cools the summer, place of capture of the solar contributions in winter, it is a place of exchanges and breathing for the project, its beating heart where the man and the air transit. Here converge and then flourish flows. The fresh air captured at night by his feet escapes by convection via the enslaved canopy that caps it.
This central hollow, bordered by a porous line of prismatic columns, which filters the light like the busy silhouettes, this hollow is surrounded by a first crown, that of circulations serving the workspaces.
The prefabricated concrete colonnade, whose singular form makes it possible to get rid of any railings, constitutes the first structural line, but also a protective plane arranged between the public reception areas and the more intimate work places. The second concentric crown accommodates useful spaces, working, adorned with raw concrete, on the walls as on the underside. Free of any leading elements, these spaces are flexible and evolving at will. The partitions as networks included in the technical floor participate in this scalability. The outer contour, forming the closed / covered, is the second supporting line alternating full piers and full height bays. This outline proposes in as well as outside two noble and perennial concrete facings, while serving the thermal insulation, included in these elements of pre-walls insulated also prefabricated. The third crown is a space for mediation and complementary uses, climate mediation, architectural and urban mediation vis-à-vis nuisances nearby. The entire perimeter of the building unfolds and welcomes in a thick and useful facade an in-between accessible where to put a foot outside.
Porous epidermis, the plane of glass and aluminum that surrounds it, itself breathes, exchanges and protects. Each fixed glazing, arranged in slightly inclined scale leaves in contact with the full aluminum parts, a blade of air that feeds reduced flow this intermediate space.
Cold air is trapped in winter to preheat it. In front of the covered skies, the envelope of glass and aluminum, all closed shutters, expresses itself as a shallow protective plan, punctuated by the gradual hatching, the gradual loosening of the solid parts, the higher the floors. Rhythm formed by the movement of the air, a rhythm where the number of air knives in contact with the solid parts and glass scales increases in the lower part, to favor the ascension principle of the natural convection.
In fine weather, other settings prevail, to open this in-between all the winds and drafts. Faced with bluish skies and direct solar radiation, the envelope of glass and aluminum widens and thickens, flaps open flags, as desired by users, give this envelope a more pronounced relief.
In the winter position, sprouted, the gray of the sky shimmer on this envelope.
As soon as the blue appears and the building follows, the envelope widens, opens reveals its depth.
In both positions, it is also the atrium that changes regime. Here we see the slave valves that open the supply of fresh air or closed isolates it.
Outside the limits of this first volume, two other extensions also find their place: lurking in the garden while protecting it, it is the volume of a glazed hall in simple ground floor which completes the spaces dedicated to the PôleEmploi. The metal structure frees a capable space lit on all four sides. Second extension coming to exploit the calm of the pedestrian crossing recreated in the southern hold of the plot, the joint program of housing widens too by proposing deep spaces of mediation, loggias intimated by the plan of the screens-screens which are intercalated circulations and storerooms of external storage. Offices and housing are then combined in a complicit way, adopting the same materials and implemented. Each metal element, smooth vertical or solid panels, is in one piece. Composed of extruded aluminum components, they are massive and without assemblies. Studied very early on, the principle gave rise to a specific industrial production, with the creation of an ad hoc sector. Finally, last perimeter, that of this crossroads where tramway and boulevard offer their animated landscapes. Perimeter from which we perceive the variations and withdrawals of a basement which serves as a base for the almost perfect prism of the main volume, carapace cube of multiple facets. Cube animated by the hatching of the vibratic rhythms of a useful envelope.