This project, for which the competition occurred in 2008, is the result of a complex transformation process in the city along with a precise economic context. Located on the former site of the Renault factories in Boulogne-Billancourt, the concerned project is part of the Trapèze Ouest, one of the sector of the operation Ile Seguin-Rives de Seine, amongst the most important emerging centres in Ile-de-France. It consists of a new mixed use neighbourhood, residential and dynamic altogether, at the cutting edge in sustainable development. Each block of the Trapèze is the object of an architectural amalgam of high level. The harmony between open-market and social housing, offices, green spaces, commercial premises and public facilities, along with the ambitious cultural vocation of the Ile Seguin, are all elements that contribute to creating an exceptionnel living space on the immediate west side of Paris. In this territory, public and private interests are evidently bound to cross. The segregation of disciplines omnipresent in the french system is antagonistic to this approach and it is manifested in the clear separation between the practices of urban planning and design, architecture, landscaping and project management. Certainly, collaboration is existent, but the large number and diversity of participants causes a normalized rarity in the points of intersection between the many different visions. A programme and volumes rigorously defined, diminished costs of construction, the hit of an economic crisis, a private real estate system that isolates the site designer, strict certification labels... this abruptly depicted a reality, that any idea, vision or architecture is one day bound to face. The first step of our work consisted in drawing from this hostile context a fruitful questioning: « In a framework where the ability of the architect is knowingly limited and in a context where economic conditions are uncertain, how to imagine an architecture capable of resisting disruptive change? That can reassure in moments of instability? And face situations of crisis? An architecture that can justify itself by itself and in any moment? What would then be the cardinal values on which to base our intervention? ». In difficult moments, one must return to fundamentals and choices are narrowed: it is simply survival instinct. With this projects we decided to face the most challenging scenarios from the very first sketch. In this operation we have let aside exhaustive studies on urbanity and potential grabbing –costly and previously explored methods at the agency–, to pivot back around an essential postulate: a space exists only if it is built. Simplification, substraction and timeless values drew the three guidelines for 70° Sud, whose name was chosen by the client’s Marketing team. Simplification: from a technical point of view, a way to reduce cost. A single detail drives the wholeness of the project: window–corridor-–railing. Within this ensemble, we can also include solar protections and openings. Substraction: the structure becomes façade, exposed concrete, no superfluous elements, no gratuitous ornement. Timeless values: to attract people, the strategy put into place is found upon incontestable building qualities: light, orientation, views and organization. If each individual is allowed to act upon his dwelling in regards to his own taste and needs, the fundamentals that make for quality are, in this building, unchangingly insured. The project suggests a built form that is simple and readable. The South and East façades are punctuated by multiple larges openings, extending the interior of the dwellings to exterior corridors running along the building. Larger balconies are inserted at intervals in the line of the terraces, projecting out. The juxtaposition of protruding, punctual and linear elements give the impression of a slender and lighter building onto Yves Kermen and Emile Zola streets. The building fulfills its role as a corner element and provides a clear distinction from the surrounding buildings. Plays with solids and voids, horizontals and verticals, light and shadow, glass and curtains, give the façade both sobriety and animation. To the simplicity of the drawing is added the richness of the material. We have sought for a finish that is clean, shaven and refined but rich enough to reflect light, and communicate with the colours of its environment.