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Commissioning: Existing Building Commissioning (Recommissioning)

Recommissioning, or “retrocommissioning,” existing building systems of any age  can reduce energy consumption, improve indoor air quality, and improve temperature and relative humidity control. In addition, it is an opportunity to analyze the air and water system balance within a building and optimize distribution system performance. In a building in which multiple architectural renovations have taken place over a period of time, recommissioning offers an opportunity to re-evaluate the mechanical and electrical systems in light of the new building arrangements, aspects of “small” renovations which are often ignored during their implementation.

The following are some of the basic steps in the process of commissioning existing buildings:

  • Meet with the facility owner, and designated user groups and operating engineers as appropriate, to understand the desired system performance for the building. This usually involves the owner delineating what is currently wrong with the building and the commissioning consultant translating that information into a positive description of what the owner wants. The product of this “investigation” is a document – similar to a Design Intent Document – describing desired system performance.

  • Interview the building owners, occupants and operators to learn the history of the building and its systems.

  • Review as many of the available original and subsequent renovation design documents as possible to trace the retrofit history of a building and the effect those retrofits have had on current system performance.

  • Analyze the existing system’s ability to meet the owner’s operational requirements, especially in light of any changes in those requirements since the building was constructed. For example, when many older buildings were built, there was little or no thought given to energy costs, whereas current building owners are likely to be very energy-conscious. Energy savings goals may be an important part of the owner’s operational requirements.

  • Perform hands-on operational tests of the existing systems in order to understand and document current control strategies and identify possible equipment malfunctions.

  • Make recommendations for modifications to the existing systems in order to better achieve the owner’s performance goals. These recommendations can include anything from current equipment, controls, and rebalancing.

  • Work with the owner in planning, phasing, and implementing the recommended modifications. From this point, the existing building commissioning process reverts back to the design-through-occupancy mode of commissioning because the project has turned into a design and construction project which will require attention to commissioning.

Sometimes owners request recommissioning services for newer buildings for one of the following reasons:

  • The building has never “worked” as desired.

  • There is no documentation about how the building is supposed to work and the operating engineers cannot figure out why.

This is a situation where the owner’s expectations of the building have not necessarily changed - they just have simply not been met. The same recommissioning steps listed above apply in this situation.

Finally, recommissioning, in the literal sense of the word, implies that commissioning has previously been performed. As more new building systems are commissioned when they are built, the concept of periodic recommissioning, or “tune-ups,” will become more prevalent. An original commissioning report should contain blank test procedure forms and checklists which can be used by the operating engineers at any time in the building’s life to confirm and re-verify that all systems are functioning as originally intended.



Engineered Systems, November, 1998

Rebecca Ellis, PE, LEED AP, CCP, CxA
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318