This research report issued by the Lawrence Berkeley National Laboratory describes a process of building commissioning to detect and remedy problems. Such problems include design flaws, construction defects, equipment problems, and needed maintenance. A methodology was developed based on analyzing 224 buildings. HVAC presented the most problems. New buildings have three times the defects of existing buildings. System-level interactions were tested. Problems were found in valves, filters, controls, etc. Non-energy benefits include improved equipment lifetime, productivity, and indoor-air quality. Detailed data and charts are included.