ASHRAE Journal - December 2019 - 19

TECHNICAL FEATURE

equipment or AHU replacements, and some envelope
improvements like window replacements.

Conclusions

From our study of 28 sites that were retro-commissioned over a period of six years, we found the average
persistence in that savings at the end of 2017 to be 61%,
with a higher persistence from projects that were retrocommissioned in 2010/2011 (76%) than projects retrocommissioned in 2013/2014 (49%). Results are inconclusive as to whether persistence between program years
is signiﬁcant; there was signiﬁcant variability in persistence from site to site.
We also considered which factors in the building had
the biggest effect on persistence and the following factors showed the highest correlation:
* Sites with an external contractor handling building
automation changes had higher persistence.
* Sites with lower staff turnover, where building
managers had retained positions longer, had higher
persistence. Formal training of these staff also improved
persistence.
* Sites that had not undergone signiﬁcant system
retroﬁts had higher persistence: whenever a site had
undergone some type of signiﬁcant system retroﬁt, persistence was generally lower.

Recommendations

* These results, especially the correlations, suggest
ways to improve persistence in RCx efforts (some of
which would also be applicable to new building commissioning):
* Building operator training (union, BOC program,
etc.) had some positive impact on persistence. The most
conscientious building operators seemed to make a
direct connection between their training and the RCx
project.
* Utility programs that promote RCx should include
persistence in all conversations with customers, and
even provide incentives for activities that promote persistence.
* Persistence could be increased signiﬁcantly with
even minor follow-up activities, which could be applied
to all sites or just to those that exhibit the problem factors discussed above. Follow-up activities include:
* Brief re-visits to sites to spot check implemented
measures. Similar to the site visits conducted for this

study, spot checking requires less time than RCx and can
result in identifying measures that haven't persisted but
could easily be readjusted to improve performance.
* Full monitoring-based commissioning generally
solves the persistence problem although it adds expense
and possibly security issues. A lighter-touch to a monitoring-based Cx approach would still have value in many
buildings. Projects with signiﬁcant enough savings to
track via utility bills or main-meter readings (e.g., chilled
water) would be good candidates for this approach.
* There is value in conducting RCx again three to six
years after the initial RCx in buildings where it can be
identiﬁed that measure performance may have degraded (based on either a signiﬁcant number of degradation
factors being present or increase in metered energy).

References

Bourassa, N.J., Piette, M.A., and Motegi, N. 2004. "An evaluation
of savings and measure persistence from retrocommissioning."
Conference Proceedings from the 2004 ACEEE Summer Study on Energy
Efﬁciency in Buildings. Paciﬁc Grove, Calif.
Database for Energy Efﬁcient Resources (DEER). 2016. California
Energy Commission. http://www.deeresources.com/.
Eardley, M. 2007. "Persistence tracking in a retro-commissioning
program." Conference Proceedings from the National Conference on
Building Commissioning.
Mills, E. 2011. "Building commissioning: a golden opportunity for
reducing energy costs and greenhouse gas emissions in the United
States." Energy Efﬁciency 4(2): 145-173.
Peterson, J., Ho, B., Lai, H. 2005. "Evaluation of
retrocommissioning results after four years: a case study." National
Conference on Building Commissioning.
Potter, A., Friedman, H., Haasl, T., Claridge, D. 2002. Investigation
of the Persistence of New Building Commissioning. Berkeley,Calif.:
California Energy Commission Public Interest Energy Research
Program, Lawrence Berkeley National Laboratory.
Roberts, J., Tso, B. 2010. "Do savings from retrocommissioning
last? results from an effective useful life study." Conference
Proceedings from 2010 ACEEE Summer Study on Energy Efﬁciency in
Buildings. Paciﬁc Grove, Calif.
SBW Consulting, Inc. 2010. Final Report 2006-08 Retrocommissioning Impact Evaluation. San Francisco: California Public
Utilities Commission.
Selch, M., Bradford, J. 2005. "Recommissioning energy savings
persistence." Conference Proceedings from National Conference on Building
Commissioning.
Tetra Tech. 2011. Comprehensive Process and Impact Evaluation of
Recommissioning Program-Colorado. Madison, WI: Xcel Energy.
The Cadmus Group. 2012. Impact and Process Evaluation of Efﬁciency
of Efﬁciency Maine Trust's Retro-commissioning Pilot Program. Augusta,
Maine: Efﬁciency Maine Trust.
The Cadmus Group. 2010. PaciﬁCorp Recommissioning 2007-2008
Utah Program Evaluation. Portland, Ore.: PaciﬁCorp.
Toole, C., Claridge, D. 2011. The Persistence of Retro-commissioning
Savings in Ten University Buildings. Texas A&M University.
D E C E M B E R 2 0 19

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ASHRAE Journal - December 2019

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