The paper presents the technical design concept for a low-cost building communications network that will allow most building equipment loads, including individual light fixtures, operable window blinds, motors and environmental sensors, to be controlled and monitored from an existing Ethernet. IBECS (Integrated Building Environmental Communications System) is a practical networking system that will provide building managers with an unprecedented degree of control over most building electrical loads, allowing them to implement load shedding, real time pricing and aggregated building load strategies with confidence. At the same time, IBECS will let individual occupants exert appropriate control over their environmental conditions (light and, ...