Using the flexibility within energy generation, distribution infrastructure, renewable energy sources and the built environment is the ultimate sustainable strategy.Clearly the energy demand characteristics of buildings, available from Building Energy Management Systems, are very valuable information for grid optimization.Our research is aimed at developing, implementing and evaluating new process control strategies for improving the energy interaction within the building, itsenvironment and the energy infrastructure by effectively incorporate the occupant's behaviour. An integral approach is used which divides the whole system in differentlayers from user up to centralized power generation. On different scale levels from individuals towards building level possibilities are being investigated both withinlaboratory conditions as well as in a real office building as case studies. Specific control strategies were applied on the existing HVAC systems. First results showedthat in the process of developing the optimal interaction between Smart Grid and the nanoGrid of a building, not only a contribution towards the optimization of theSmart Grid control can be offered. New individual HVAC systems and new occupancy based process control strategies could lead to energy reductions (20-30%)and even improved perceived thermal comfort.