Retro-commissioning (retro Cx) is a building tune-up and more that can decrease the energy consumption of your building while potentially increasing indoor air quality, employee productivity and property value. It’s more than an energy audit because it doesn’t just simply tell you something is wrong; it tells you exactly what is wrong and what should be done. The right commissioning provider can show you ways to enhance your system beyond its original design intent.
Commissioning is a quality process that is used during new construction and renovations. Retro-commissioning is a similar quality process done post-construction, whether it’s one or 10 years later. The commissioning industry grew out of the realization that construction teams are struggling to set up building systems correctly. The result: many buildings don’t perform to their design performance levels, and in some cases to the design intent, wasting energy and losing installed system expansion capacity.
To make matters worse, once the building is turned over to often over-worked, under-paid maintenance staff, the building performance generally degrades quite rapidly. Why does this happen? Lack of training and budget challenges are two common reasons, but mostly because they don’t fully understand how the system is supposed to work and why. Those who do understand how the systems work often still might not understand why. In contrast there are many buildings with systems installed very close to the design intent and maintained by top-notch staff but that have design problems that were never revealed or that fell on deaf ears.
Look for Experienced Specialists
Commissioning providers are not any smarter than engineers, construction teams and facility operators. Then why, you ask, is it that the retro-commissioning provider is the one who finds all these problems? The reason is that this is what they do and it’s all they do. The tasks involved in designing, constructing and maintaining a building are seemingly endless. It’s easy to get wrapped up in your own daily responsibilities. Retro-Cx requires highly trained and experienced individuals who are not only adept at finding what’s wrong but also figuring out what’s missing.
Although any building system can be commissioned, the general industry focus is on those systems that impact energy consumption and occupant comfort such as HVAC systems. With retro-commissioning there are basically two levels: LEED for existing buildings (LEED-EB) and everything else. LEED-EB is an industry standard. With LEED-EB, the U.S. Green Building Council (USGBC) has outlined what is expected from retro-Cx which includes formalized testing plans and procedures as well as the development of a Building Systems Manual.
While all good stuff, it can sometimes be taxing on one’s budget. For those not seeking LEED certification and with limited budgets, a more cost-effective approach could involve skipping the documentation and having an experienced Cx team jump right into system testing. Using their experience, they can exercise the equipment through the sequence of operations and prepare a simple report of the findings. The result can be comparable and cost less, but will not have the LEED level of documentation or the building systems manual. The owner or facility operator can work with the commissioning provider to define a scope of work that meets their needs.
Three Findings Categories
The findings are generally grouped into three categories: no cost, low cost and capital improvement. “No cost” findings are generally items the maintenance staff can fix on their own. “Low cost” findings are items that may require a service provider, but the costs are generally low and can be done within the facility budget. Repairs or simple system sequence enhancements are low cost because most, if not all, of the components needed already exist. “Capital improvement” findings generally result in equipment replacement and require a high-level decision process.
Some examples of “no cost” findings: missing filters, dirty cooling/heating coils, replacing defective chilled/hot water valve actuator, incorrect BAS set points, missing equipment on/off schedules. Examples of “low cost” findings: implementing static pressure reset, implementing supply air temperature reset, programming standby modes, calibrating controlling sensors, and implementing condenser water reset. Examples of “capital” findings: replacing defective or inefficient chillers, replacing old AHUs, replacing antiquated building automation system, renovation project for more energy efficient design, and lighting replacement project.
The savings associated with retro-commissioning vary with building size, use and age but generally can result in energy savings ranging between 5 percent and 20 percent. Depending on the retro-Cx approach taken, the payback on the investment is generally less than two years, with many projects falling below one year. It’s important to realize that the energy-saving potential found with retro-cx will require cash outflow in the form of repairs or capital improvements. The cost of repairs or improvements is not included in the numbers above.
Mix of Engineers, Programmers
Retro-Cx requires a highly experienced team and ideally one that has a mix of senior engineers and senior tradesmen such as BAS programmers. Unlike new construction commissioning where the engineer of record and the contractors are there to support the commissioning effort, the retro-Cx team is on their own to figure out the design intent and design system capacities and to verify system operation. This is even more of a challenge with buildings that have lost their as-built construction documentation.
Retro-Cx has been around a long time in various forms but mostly from service providers trying to recommend a solution to a problem. Many service providers are considered by owners to be trusted advisors, and for good reason. However, a word of caution: these service/trusted advisors are generally not design professionals. Many retro-Cx energy-saving findings have been the result of good intentions from service providers who did not understand the original design intent, principles of design and psychometrics. The intent of this caution is not to suggest getting rid of one’s trusted advisors, but rather to recognize potential limitations and to keep everyone in the capacity to which they are best suited.
Retro-commissioning is not new. Owners have been looking for ways to reduce their operating budgets through energy reduction for years. What is new is the level of attention it’s getting. With both AIA and ASHRAE committing to drastic reductions in the energy consumption of new buildings in the years to come, a lot of emphasis is being placed on the buildings already built to lower energy standards, which is basically every building. Whether it is the fear of skyrocketing energy costs or the need to cut costs in the face of an economic downturn, retro-Cx is a proven way to reduce operating costs.
Bill McGuire is the director of commissioning at X-nth. He has been working in the HVAC industry for more than 18 years. He can be reached at bmcguire@x-nth.com.
