The demands for both thermal comfort and reduced energy consumption in buildings have become a major driving force for the increased use of advanced building automation and control systems (BACS). In the on-going development of Zero Emission Buildings (ZEBs), it seems to be a common understanding that such systems are needed in order to save energy and reach the zero emission goals, and that energy consumption for their operation is negligible compared to the building needs and the energy saving potential BACS causes.

However, sensors and actuators in automation and control systems require electricity to operate, and both the environmental impact related to this operation, and the manufacturing and maintenance of electronic components (including wiring) is not well understood in a Life Cycle Assessment (LCA) perspective, even though different standards give framework and methods for energy calculations and LCA of buildings. These standards unfortunately do not include or suggest default values for the auxiliary energy from different levels of BACS. Usually, in building simulation, these values are only assumed to be a part of a fixed internal gain, e.g. as in the Norwegian passive house standard, with no further considerations on the actual operating energy or the environmental impact it represents.