In recent years the topic of persistence of benefits has gained more interest both for existing building retrocommissioning and new building commissioning. This topic is relatively new, and the only relevant projects identified in the literature to date involve a total of 27 retrocommissioned buildings and 10 new buildings. In retrocommissioned buildings, savings generally decreased with time.
10 buildings in Texas:
o cooling savings dropped from 44.8% to 35.1% from 1997 to 2000
o heating savings dropped from 79.7% to 49.7 % from 1998 to 2000
o retrocommissioning savings in 2000 were 985,626/yearcomparedwith1,192,000 in 1998
o three fourths of the decrease was caused by component failures in two buildings
Eight buildings in California:
o peak aggregate savings occurred in years two and three
o about 1/4 of the savings disappearing in year four (year 4 data available for only four buildings)
Three buildings in Oregon:
o 89% of the electric savings but none of the gas savings in three of the Oregon buildings persisted four years later.
One building in Colorado:
o 86% of the savings persisted after seven years
In new buildings (after at least two years)
o over half of the fifty-six commissioning fixes persisted
o hardware fixes, such as moving a sensor or adding a valve, and control algorithm changes that were reprogrammed generally persisted.
o Control strategies that could easily be changed, such as occupancy schedules, reset schedules, and chiller staging tended not to persist.
o persistence is also related to operator training
