This simple case study presents the argument for Measurement and Verification and System-Wide Commissioning/Re-commissioning as part of an energy retrofit project.
Measurement and Verification (M&V) is a process used to identify the specific impact produced by a material change. With respect to energy retrofit projects in buildings, M&V is a systematic approach used to determine the energy savings produced through the retrofit. As described by the International Performance Measurement and Verification Protocol (IPMVP), M&V can take several different forms and can range from whole building metering down to metering and data collection of individual devices; or anywhere in between.
For every project a suitable M&V approach should be selected based on three key metrics; 1) the ability to isolate the energy use/savings from the retrofit, 2) cost of implementation, 3) measurement feasibility. Once an M&V approach is selected for a project the Pre-Retrofit data should be collected and the ‘baseline’ for comparison can be established. Upon completion of the energy retrofit and collection of the Post-Retrofit data, the comparison can be made to validate the expected energy savings.
One approach to M&V that this author is quite used to seeing is the method of “assuming all of the savings are achieved”. It is often true that energy retrofits will realize the full savings potential without undergoing a detailed M&V process; however, without at least applying an IPMVP Option C (whole building) approach there is no way to know if the savings have materialized. Particularly in this day and age where mechanical and electrical building systems are increasingly complex and interconnected, and where third-party automation systems are often integrated it is easy for bugs and unintended consequences to work their way into the system.
Efficiency Engineering Inc. encountered one such example of the above on a recent chiller retrofit. Good engineering principles were applied to the retrofit design and the construction was completed as intended and the replacement chilled water system performed to provide comfort cooling to the commercial facility in question. Significant savings were expected as was an incentive of $30,000 for a 100-ton chiller. The M&V Plan called for temporary pre and post-retrofit metering for a two week period to validate the energy savings. The project also involved modification to the building automation sequences of operation to accommodate the installation of the new chilled water equipment. Upon completion of the work, a routine performance Verification of the Building Automation System revealed that all of the chiller plant operating sequences were programmed, commissioned, and tuned as desired. However, the post-retrofit chiller metering did not reveal the expected savings. In fact, only half of the savings had materialized.
Upon further investigation of the building automation system, we found that the BAS contractor had inadvertently changed the programming of the outside air dampers to open them fully during the unoccupied hours even if free cooling was not available. This resulted in a lot of very warm, humid air being introduced to the building that the chilled water system had to cool and dehumidify.
What ended up as a relatively simple fix would not have been determined without this post-retrofit Engineering work. Not only would the incentive have been reduced by 50%, but the Client would have suffered from higher energy bills for years to come.