Christian de Nacquard is Head of the Energy Lab within the R&D and Innovation Department at Bouygues Construction, where he leads strategic research programs on energy performance and large-scale building renovation.  With over 25 years of experience in sustainable construction, he specializes in deep energy retrofit, low‑carbon technologies, and the integration of renewable energy systems in existing buildings.  He has coordinated multiple European R&D projects under Horizon 2020 and Horizon Europe, and actively contributes to the development of innovative, industrialized renovation solutions. His work focuses on combining technical performance, economic viability, and carbon reduction to accelerate the energy transition of the building sector.