Describes:- - a structured list of Building Automation and Control System (BACS) and Technical Building Management (TBM) functions which have an impact on the energy performance of buildings; - a method to define minimum requirements regarding BACS and TBM functions to be implemented in buildings of different complexities; - a factor based method to get a first estimation of the impact of these functions on typical buildings; - detailed methods to assess the impact of these functions on a given building.