The Nano-Innov@Saclay 125 project is part of CEA Saclay’s Multi-annual Programme for the Improvement of Energy Performance of Buildings (PAPE). This is an operation to rehabilitate a building (Building 125 in Saclay) to bring together the five teams of the CEA-CNRS NIMBE Joint Research Unit on a platform meeting the best standards of functionality, comfort and sustainable development: the Nano-Innov@Saclay platform. The project is guided by an ambition of global environmental exemplarity that incorporates demanding technical choices, such as the control of acoustics, olfactory nuisances, water management, waste management, etc. Due to the atypical nature of the site, which is very energy-using due to laboratory activity, the “energy management” target of the HQE benchmark has been positioned at the “High Performance” level for this project. The minimum objective is to build a “existing” BBC (Lower Consumption Building) building according to the 2005 RT 2005 “per element”, with a very significantly reduced overall energy consumption (-70 %). This poses a real technical challenge in terms of the type of building, combining energy-intensive offices and laboratories, making it all the more difficult to control energy consumption and therefore requires research and implementation of the best available technologies in order to ensure a significant impact.