States that modern energy management and control systems have alarm and trend features that allow building operators to monitor and troubleshoot building systems. However the size and complexity of building systems has led to data overload at the operator workstation. Tools and algorithms are needed to consolidate the information that arrives at the workstation into a clear picture of the system status. Describes one such algorithm for monitoring control performance and presents laboratory and real building data from variable air volume boxes that demonstrate the utility of the algorithm for isolating faults. The algorithm compresses large volumes of data into a small number of indices that can be used to quickly assess the performance of control loops. Indices can also be computed that allow building operators to identify actuators and valves that are wearing out prematurely due to excessive movement.