This paper summarizes key results of ASHRAE Research project RP-1137, which sought to quantify the benefits and longevity of the recommissioning process on variable air volume (VAV) systems that incorporate direct digital control (DDC). Field testing was completed in three diverse facilities over a period of up to two years, generating three data trends. General performance indicators were compared using the data collected prior to commissioning, immediately after commissioning, and long after commissioning was completed (a minimum of six months later). Key performance indicators included : improved DDC system accuracy, indoor air quality (IAQ), and energy efficiency/savings. It is important to note that RP-1137 did not seek to determine all possible recommissioning benefits, only to quantify some of the benefits using field testing and laboratory experiments. This research indicates that commissioning is beneficial and that system recommissioning is typically justified within a time period similar to the capital payback period. Conclusions are limited to the time period specified ; thus, the longevity of recommissioning is at least equal to the payback period but cannot be predicted beyond this within RP-1137.