A method and apparatus is disclosed for assessing performance of control applications in an environmental control network and for diagnosing performance problems. The apparatus includes a performance assessment and diagnostic display comprising a facility navigation tree, a system navigation tree and a performance/diagnostics window. The facility navigation tree and system navigation tree may be used to select the facilities and systems that are to have their associated control applications assessed and/or diagnosed. The performance/diagnostics window includes graphs of performance indictors that are indicative of performance levels for the included control applications. The system tree may be used to delve to more detailed views of the performance indicators to obtain additional information that may help to diagnose problems noted in performance of the selected control applications.