Distributed control and energy management for buildings is a viable solution, ensuring both indoor comfort for the occupants and reduction of energy consumption. The aim of this paper is to present the architecture of a distributed building energy management system that can be installed in new as well as in existing buildings, which are more energy inefficient. The system integrates a smart card unit, acting as a user machine interface, sensors, actuators, interfaces, a PLC controller that incorporates the fuzzy control algorithm, local operating network (LON) modules and devices and an optional PC which monitors the performance of the system. The distributed control architecture is based on the properties of the LON. The complete system is installed and tested in the Laboratory of Electronics of the Technical University of Crete.