QSE Logo

LetsTalk2015@QSEng.com
612.308.4716

Retrocommissioning New Buildings

I just completed reports for two retrocommissioning studies for different building owners. An interesting – and potentially puzzling - similarity between them was that they were both for relatively new buildings. One was a building that had been completed just one year before the owner decided retrocommissioning would be a good idea. The other was a four year old building. Both were larger than 100,000 square feet.

The building owners quickly identified their new buildings as energy hogs compared to their expectations and similar building types, and they took advantage of the local utility’s recommissioning rebate project to fund an analysis. Neither building had been commissioned as part of its original design and construction program.

In the case of the one year old building, the utility needed to think twice about the application for funding retrocommissioning in a brand new building. The owner justified the need by pointing out that there should be energy savings available that weren’t realized through a formal commissioning process in the initial project. This was an interesting twist for a utility that offers recommissioning rebates but hasn’t introduced a new construction commissioning rebate program yet.

The bottom line for the two projects was identification of energy conservation opportunities (ECO’s) resulting in 15% and 30% of the one year old and four year old buildings’ energy costs, respectively.

In the case of the one year old building, there were many ECOs associated with system operation which is the primary focus of most retrocommissioning projects.

  • Control sequences that were not programmed as originally designed
  • Controls that were overridden to operate differently than originally designed
  • Sensors out of calibration (all air flow measuring stations and 25% of sampled temperature and humidity sensors)
  • Control loop hunting
  • Opportunities for reducing ventilation and/or airflow under low load conditions.

All of the above could have conceivably been identified and corrected through a new construction commissioning program. As it stands now, the owner will have to foot the bill for correcting most of these problems because the standard one year warranty period is over.

Not included in the 15% annual savings, however, were energy issues directly related to “value engineering” decisions made during the original project. It is not clear how much attention future operating costs received when design decisions were initially discussed, but the on-going economic reality of those decisions is overwhelming to the owner. It is now impractical for the building owner to change the systems based solely on available energy savings.

In the four year old building, most of the ECO energy savings involve capital improvements that the owner recalls being eliminated from the original project for budget reasons. In the case of this building, which currently operates continuously at full capacity, the energy savings do provide a reasonable payback for the addition of isolation dampers, variable speed drives, and the controls necessary to schedule operation of systems or parts of systems on an as-needed basis.

There are also a number of operational ECOs in the four year old building that offer a quick payback. However, as a percentage of total energy consumption, they pale in comparison with the items initially “value engineered” out of the building.

The lessons learned – which are pretty much old news for building owners who care about their energy consumption – are:

  • Value Engineering and Life Cycle Cost Analysis

Many owners are unwilling to pay for and/or don’t value a detailed life cycle cost analysis (LCCA) for major system design decisions. In addition, LCCA takes time which is often not budgeted into a project’s design schedule. However, paying a consultant after the fact to model current building systems performance compared to proposed modifications to those systems could be an exercise in futility if the owner is unable to finance implementation of the modifications (even with utility rebates). In the case where the owner can finance the modifications, how much excess energy is consumed between initial occupancy of the building and implementation of the energy conservation measures?

  • Commissioning: Pay Now or Pay Later.

There is so much value to be gained by a capital project commissioning program. A comprehensive commissioning process starting in the pre-design phase could help avoid all of the problems identified in these two new buildings – or at least prepare the owner for the long term reality of decisions made. Even an end-of-construction, testing-only commissioning process would have helped find and resolve the operational issues earlier and, arguably, for a lower cost.

 

COMMISSIONING: GETTING IT RIGHT

Engineered Systems, February, 2007

by
Rebecca Ellis, PE, LEED AP, CCP, CxA
President
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318
rteesmag@QSEng.com