Retro-Commissioning (RCx), sometimes referred to as Existing Building Commissioning (EBCx), is an important process for optimizing the performance of existing buildings. It involves the comprehensive evaluation of a building’s systems, their components, and how they interact with each other. The goal of RCx is to identify areas of improvement in the building’s operation maintenance, as well as system’s design, to help make it more energy efficient, reduce operating costs, and improve occupant comfort and safety. In this article, we will explore the RCx process and the benefits it can bring to building owners. We’ll also cover some easy-to-recognize signs that your building may benefit from RCx and how to make the most of the RCx process.


There are two possible paths for retro-commissioning: an incentivized program through your local utility provider or a non-incentivized program working directly with an RCx provider. Incentivized programs typically have specific requirements, such as a minimum building size or a limited scope of systems that can be covered by the program. However, the cost of the RCx survey, investigation and implementing the energy-saving measures can be substantially offset by the utility company. While a non-incentivized program may be more costly, it allows for more leeway, meaning the potential for even higher energy savings. If your building does not qualify for your utility provider’s RCx program, your facility can still benefit from having these services performed.

What’s going on? The Survey Phase

The RCx process typically starts with a meeting between the RCx provider (RCxP) and the facility staff to discuss the known problems in the building, such as increased energy costs or poorly performing systems and equipment. The RCxP can then take a closer look at past utility bills to analyze the historical data, evaluating how the building has performed compared to comparable buildings (similar geographical area, weather conditions, etc.). Prepared with the background knowledge needed to dig deeper, the RCxP will walk through the facility, performing a physical inspection. They’ll look at the age and condition of the equipment, as well as how everything has been maintained over time. They will also test the systems and equipment to see how they are performing. Are they meeting the original design criteria? Are there known problems with how the equipment functions? If the building use has changed over time, have they been adjusted to perform in accordance with the building’s current use?

How can we improve? The Investigation Phase

After identifying any deficiencies and gaps within the systems, the RCxP will generate various energy conservation measures (ECMs) to resolve the issues plaguing the building. These opportunities can range from minor tweaks to optimize system performance to major physical changes to satisfy the building’s current needs. The RCxP will model the performance of each ECM to determine how much energy it would save, then calculate the associated cost savings. In this stage, the RCxP would also get hard installation costs from qualified contractors to complete the work. The projected installation costs, including RCxP oversight, is divided by the estimated annual cost savings to calculate the simple payback. For example, if the estimated annual energy savings is $20,000 and the implementation cost is $40,000, the simple payback, or ROI, would be 2 years.

Where do we go from here? The Implementation Phase

All of the information gathered and developed by the RCxP is compiled into a report and presented to the owner. With guidance from the RCxP, the owner will select the EMCs they want to implement. They will then help the owner manage the installation, providing oversight and commissioning services on the implemented measures to confirm that they are installed and performing the way they were intended. In addition, the RCxP will make sure the facility staff is properly trained on the changes to the systems, providing them with as built documentation and O&M manuals. At the conclusion of the implementation stage, the RCxP will develop a final report that confirms everything has been installed properly and is operating as intended. If the owner is following an incentivized program, the RCxP will also be able to help with any paperwork and documentation needed to receive finalize the incentives with the utility company.


Retro-Commissioning has a wide range of benefits, and it may differ depending on the facility and the priorities of the owner. According to Lawrence Berkeley National Laboratory’s study, “Building Commissioning Costs and Savings Across Three Decades and 1,500 North American Buildings,” most recently updated in 2020, the top six reasons owner’s pursue RCx are:

  • Obtain energy savings – 70% of the study’s respondents reported that their projects experienced energy savings of at least 10%. In addition, 58% of the respondents stated that the simple payback was less than two years. RCx projects that are not part of a utility program can experience even higher energy savings, upwards of 20%
  • Ensure system performance – improving the energy efficiency of your systems and equipment leads to reduced energy consumption and reduced utility bills.
  • Ensure or improve thermal comfort – If you’ve had a lot of hot and/or cold complaints from building occupants, RCx is a great way to get to the root cause of the issue so it can be corrected.
  • Ensure adequate indoor air quality – the health and safety of building occupants is top of mind for many owners. Improving the indoor air quality of your facility can result in happier, healthier occupants.
  • Train and increase awareness of operators or occupants – In order to maintain the excellent energy savings from RCx, it’s important to train the facility staff and occupants. Using and operating the building day-to-day, they are a key component in continued energy savings.
  • Qualify for rebate, financing, or other services – if it’s available, financial support from a utility provider is a great way to offset the initial costs of retro-commissioning. These programs tend to be fully funded and underutilized, meaning the money is already there waiting for you!

All of the benefits above contribute to an overall increase in the value of the building asset as a whole. Simultaneously addressing poor system performance, comfort issues, indoor air quality and lowering energy costs while increasing the value of your asset is a win-win scenario.


  • Increased energy consumption – energy consumption can change seasonally depending on the type of utility used by your heating and cooling equipment, however, if you notice your energy costs are higher year-to-year, it may be a sign of inefficient or poorly performing systems. For example: your summer cooling costs are higher than last summer, but the average temperature in your area has remained about the same. The same can apply to heating costs in the winter.
  • Wear and tear on your building’s systems and equipment – maybe you’ve had to perform more service than usual such as fan motor belt replacements, or you’ve been replacing components on the HVAC systems.
  • Occupant comfort complaints – from temperature to indoor air quality (IAQ), an increased number of similar complaints can indicate that something is wrong with the systems and equipment. Signs can include complaints about their spaces feeling stuffy or drafty, smelling strange odors, or simply just complain about the temperature. There may be non-verbal signs you can pick up on by walking around the building as well. Perhaps many occupants in a particular wing have resorted to purchasing small space heaters and wearing sweaters in the winter.
  • Extended equipment schedules – If you need to start your heating or cooling equipment earlier in the day than usual to satisfy heating and cooling loads, it’s a sign that it’s not operating as efficiently as it could be.
  • Equipment running constantly – for example, an air handler is not able to meet its heating or cooling setpoint, so the heating or cooling components run constantly without cycling off.


  • Get commitment from the owner and facility staff to participate in the RCx program – These are the people with the most in-depth knowledge of the building, including everything and everyone inside of it. That knowledge is key to helping the RCxP understand what is going on and to help you effectively execute the RCx project. After implementation, the facility staff will be responsible for operating and maintaining the equipment. Their participation throughout the RCx process will help them better understand what needs to be done to keep the systems and equipment in peek operating condition in the long term, after the RCxP leaves.
  • Gather your building documentation ahead of time – drawings, testing and balancing reports, and utility billing data will help the RCxP get the full picture of your building and can help simplify the RCx investigation process.
  • Catalog any known problems in the building – collecting detailed qualitative information can help inform the RCx process as well. For example, “the system hasn’t been performing well” is not as descriptive as “the air handling system hasn’t been able to meet setpoint for six months and we don’t know why.” Cataloguing poor performance or degraded/drifting system performance over an extended period of time is even more valuable.
  • Reach out to your utility account representative or ATC vendor – they can let you know if there is an incentivized program available to you for retro-commissioning, and they may be able to connect you with an RCx provider that they know and trust.
  • Look for a credentialed RCx provider that also provides commissioning services –commissioning firms with licensed Professional Engineers and Certified Commissioning Professionals have extensive background knowledge of the design and construction of various systems and equipment. Certified Energy Managers and Certified Energy Engineers are specifically trained in optimizing system performance.


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Ernest Lawas

About the Author:

Ernest Lawas is the co-founder and a Managing Principal at Sustainable Engineering Solutions. He has over 25 years of experience providing Commissioning services nationwide. Ernie is a registered Professional Engineer (P.E.) in Connecticut, New York, New Jersey, and Massachusetts. He is also a Certified Commissioning Professional through the Building Commissioning Association, a Certified Energy Manager and Certified Energy Auditor through AEE, and a LEED Accredited Professional.