In a building which has at least two floors, an apparatus for controlling and regulating room temperature having a hierarchical structure includes a predictive device on the top level, that provides optimal control of the use of at least one free energy source, and at least one device on a lower level which is used for feedback regulation of at least one additional energy source. The predictive device uses a building model and repeatedly optimizes the energy requirement or the energy costs. The regulation strategy of the predictive device uses characteristics of a passive heat accumulator of the building.