The 3 factories cited above are parts of the system of factories of Eau de Paris, treating and supplying water for the capital of France. The Energy-Efficient Renovation of the 3 factories aims to improve the comfort of the occupants during both summer and winter, while decreasing the buildings’ energy consumption at the same time. The High Environmental Quality HQE® process is applied through out all of the phases of the mission, from interior to exterior design, in order to propose buildings that produce minimum energy, and that refurbish and give new values to the existing architecture.