The building will be implanted in a very heterogeneous urban zone composed of houses, apartment blocks and several industrial buildings. The project’s departure point was therefore the challenge of being able to contribute to the definition, organisation and design of this district’s urban spaces. The first stage of our research was to question the form and its urban context, so that we could define an ensemble both maximising the plot and addressing the specific constraints of both of the project’s components.
From the outside, the building is a compact parallelepiped whose only irregularity is the large opening in the south facade, leading to the more private entity of the CSL beyond. The view/non-view and open/closed constraints of each of the project’s components are optimised by the interplay of overlapping volumes. The long, uniform rectangle of the SPIP reinforces the urban front on the avenue. Its quasi-mono-orientated volume prevents any aural or visual communication with the minimum-security prison. The volume of the SPIP forms a solid, natural frontier enabling the CSL to function in complete security in the middle of the block and shielding it from outside view. The CSL is set further back, along rue des Acacias. Its entrance is marked by the large overhang, shielding the neutral zone from view. The CSL’s main entrance and logistic and administrative zones give onto a secure and lit exterior volume, whereas the inmates’ zone gives onto the interiorised heart of the block.
The outer perforated steel layer enveloping the façade acts as a visual filter and gives the architecture a strong unitary identity. This layer acts as an initial solar protection and complements the ‘thicker’ inner thermal insulation façade. The façade consists of a structural screen in concrete, an exterior rain-protected insulation, and a metallic envelope composed of perforated sheet metal panels with a Cor-Ten effect finish. The envelope has folding and sliding shutters over the windows and follows the building’s 1.35m grid to correspond to the east/west aspects of the offices.
The perforation density of each façade varies in function of aspect, to optimise natural lighting and solar protection, and considerably increase thermal performance. CSL’s inner facades, in direct contact with the inmates’ area, are composed of robust, watertight, self-cleaning, prefabricated wall elements. Two major advantages of this innovative and rational structural solution are rapid installation and reduced production time and cost.
