This research aims to understand and analyse the interactions and negotiations related to energy optimization, in a building designed for energy performance, reached through the automating of technical adjustments. Optimizing this sociotechnical system requires a collective dynamic for learning and regulating interdependencies between three categories of actors - managers, operators and occupants. If the managers recover control functions and ensure the long-term viability of the project, the operator intervenes in the decisions of energy consumption through his technical expertise. These roles, formalized by contracts and instructions, or constrained by technical scripts, are reconstructed through day-to-day interactions. Since October 2017, the empirical observation of 18 meetings in an efficient tertiary building in Grenoble (France), allows us to analyse the negotiations around political, technical or economic issues, within an unstable space of deliberation. Empirical observation of user practices, deepened by ethnographic interviews, allows us to understand how "ordinary" practices are translated (or not) into elements of negotiation around energy, and vice versa how economic or technical decisions on energy affect the day-to-day use of the building.