Built in the 1920’s, the Halle Pajol was for many years a warehouse for the SNCF. It is over one hundred metres long by forty metres wide and is the main feature in the Pajol development zone. The Pajol development zone, a sort of eco-island, is strongly committed to a sustainable development approach, focused on renewable energies. The three sponsors involved in this development are the City of Paris, the FUAJ youth hostel organisation and the development body Semaest. The structure of the new buildings is one of the first built examples of a hybrid wood & concrete structure. The wood is used for the vertical structure and the concrete for the horizontal structure. The hybrid nature of the structure came from the twin request for a wooden building with high performance thermal inertia. The existing structure, renovated and locally transformed, is the structure for the solar power unit comprising 4,000 m² of solar panels on the roof.