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Retro-commissioning involves close examination of building systems and equipment, uncovering problems and identifying energy-saving solutions. All images: Grumman/Butkus Associates  


A well-designed lab facility will deliver a powerful combination of safety, functionality, efficiency and responsible use of resources. Most owners strive to achieve these goals in any new lab project or major renovation or addition. Performance can be documented by commissioning: third-party testing of the facility’s major mechanical, electrical and plumbing systems before a new or renovated project is turned over to the owner. In addition, building sustainability may be documented by rating systems such as LEED, Energy Star and Green Globes.

Unfortunately, even a well-designed lab’s energy performance may erode over time, due to problems with infrastructure, equipment, controls, operational procedures and lab-user techniques.

This is doubly true of buildings whose initial overall design didn’t reflect strong sustainability goals. You may have tried to keep up with the latest in lab sustainability, whether that involves high-performance and VAV fume hoods, lowered air changes per hour, presence sensors or demand-controlled ventilation. But, if the people working in offices on the other side of your building are running electric space heaters to stay warm, can the facility truly be “sustainable?”

Enter retro-commissioning: A tune-up designed to help buildings function optimally. Often abbreviated as “RCx,” retro- commissioning—also known as “existing building commissioning”—is a process led and conducted by an engineering firm or commissioning consultant that targets energy-saving opportunities in existing buildings.

RCx aims to find, investigate and solve unknown problems, using a structured process with defined procedures. An effective project will result in custom solutions to meet the owner’s current requirements. RCx evaluates the facility at the systems level, as well as the equipment level. In addition, RCx almost always includes a deep examination of the computerized building automation controls system (BAS), including schedules and sequences of operations.

Key tasks of retro-commissioning
A skilled RCx provider generally focuses on three primary tasks:

  • Evaluating performance compared with the original design intent (or the performance recorded during previous commissioning). System and equipment performance can be expected to deteriorate somewhat over time, but a significant disparity between original and current performance presents an RCx opportunity.
  • Evaluating how well the systems and equipment are serving the building as it’s currently used. Buildings are dynamic. Even in a one-year-old facility, user needs may cause deviations from the original design intent. This is particularly true for research labs, which are often designed for unknown occupants. Input from department heads and current users is invaluable; however, when actual researchers arrive, changes are almost inevitable. In addition, the most sophisticated energy-saving systems and strategies may fall apart after occupancy unless users are well-informed and well-trained. A good RCx provider is skilled at solving problems caused by differences between current usage and the original intent.
  • Optimizing building systems, equipment and BAS with the latest technology. The engineering, equipment and technology world is always evolving. Improvement opportunities often favor buildings more than three years old. For example, variable-frequency drives weren’t widely available 10 years ago, but are generally code-required for new construction today. Similarly, VAV systems with static pressure reset involve BAS sequences that were uncommon just five years ago. RCx can leverage the latest technologies to optimize the building beyond its initial performance targets and capabilities.


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Since many RCx issues involve the BAS, thorough analysis of schedules, sequences and setpoints is an important part of the process.  


A RCx provider should be solutions-focused, not only identifying issues, but also suggesting projects to address them, often termed “retro-commissioning measures (RCMs)” or “energy cost-reduction measures.” The typical project focuses on no-cost or low-cost operational measures, with paybacks usually shorter than two years. The provider’s recommendations should include potential energy savings, implementation costs and a payback period according to prevailing utility rates. This analysis helps the lab owner pinpoint the projects with the highest ROI, facilitating good decisions for immediate action and possible long-term improvements.

Potential benefits of retro-commissioning
Because of the inherently high energy use of many lab facilities, RCx can be an invaluable tool. Some of the typical results of lab RCx include:

  • Reducing energy use and associated operating costs.
  • Reducing carbon footprint.
  • Improving indoor air quality and user comfort.
  • Eliminating hot or cold spots.
  • Solving ventilation and pressurization problems.
  • Identifying safety issues and code violations.
  • Improving a facility’s Energy Star score or Green Globes or LEED status.

The good news about RCx is augmented by the fact, in many areas, local utilities will fund some, or all, of the cost of a retro- commissioning study—allowing owners to conserve funds for actually implementing some, or all, of the identified projects. Depending on the work recommended, incentives may also be available for implementation.

Here are questions that can help you decide whether RCx might be a good tactic for your lab facility:

  • Do you receive service delivery from a utility? RCx can still be useful in settings where energy is provided by the owner’s central utility system, such as central steam, but incentive programs to pay for studies may not be available.
  • Are you willing to spend any money to implement the RCx measures identified?
  • Do you have up-to-date building documentation and records available?
  • Is your building relatively large or complex? The facility need not be enormous, but a tiny lab building probably won’t find RCx as cost effective as a larger one. Similarly, the more complex the building, the greater the opportunity for improvement.
  • Does your facility have a relatively high Energy Use Index (EUI) compared with similar facilities, or a low Energy Star Portfolio Manager rating?
  • Is the building free of known major problems requiring large-scale capital repairs or replacements?
  • Does the building have a functional BAS with direct digital control (DDC)? This is typically required for utility-sponsored RCx efforts.
  • Are you and your facility operations staff committed to active involvement?
  • Are you willing to endure temporary disruptions? A good RCx provider will strive to schedule testing during times that are least disruptive to lab users, but some disruptions may be unavoidable.

Affirmative answers indicate that RCx may be right for you.


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In addition to the HVAC systems typical for commercial facilities, labs often have a complex infrastructure for dealing with liquids, gases and wastes. Systems and equipment may fail to function optimally for various reasons, including aging, maintenance problems and user choices.  


The retro-commissioning process: What to expect
Though every provider is unique, a standard outline of work applies to most RCx projects. Major steps generally include an application phase (if utility funding is involved), a planning phase, an investigation phase, an implementation phase and a verification phase.

  • Application/proposal: An application for outside incentive funding is prepared, if applicable. General information about the facility’s systems is gathered; some basic ideas about the owner’s implementation budget are discussed; drawings and operations sequences are collected; an internal project champion is assigned; and any contractual and financial documents are reviewed by the owner’s financial/legal team.
  • Planning: The planning phase includes an initial site assessment (walk-through), development of an RCx plan, collaboration with the owner’s operating engineers and controls contractor (as applicable) to review current sequences of operations, general identification of potential operational improvements, identification of potential energy-saving measures and development of implementation costs and energy-savings projections.
  • Investigation and recommendations: The RCx provider works with the owner’s team to further identify specific opportunities for improvement, and a detailed site assessment is finalized. Coordinating with the facilities staff, the provider then develops, conducts and facilitates targeted functional performance tests (FPTs) on the systems and equipment. Providers typically bring in their own equipment to verify sensor calibration, valve and damper operations, controls sequences and operation of larger systems, such as condensers and chilled water and heating. Trending data is collected and analyzed, establishing a baseline. Energy savings and payback projections are then finalized based on the field measurements and trending data. The RCx provider also typically develops detailed scopes of work and requests contractor pricing for each recommended energy cost-reduction measure. Based on the final projected energy savings and contractor quotes, the owner selects which measures to implement.
  • Implementation: The owner’s team takes over responsibility for implementing the selected measures, working with appropriate contractors, controls experts and in-house staff. The RCx provider works with the owner to troubleshoot any measures that aren’t working properly.
  • Verification: After implementation, the RCx provider should commission and help verify installation and proper operation, as well as updating energy savings based on actual measured data. Change orders are issued to contractors if corrective repairs are needed for any implemented measures that aren’t working. A final report completes the project and is submitted to the subsidizing utility (if applicable).

Depending on the size of your facility, RCx typically takes nine to 12 months from start to finish, which allows the provider to observe the building seasonally in both heating and cooling modes. The implementation phase typically only lasts two to three months.

Retro-commissioning in the real world
A pair of typical projects at a large Midwestern university provides a good illustration of the potential for RCx in lab buildings. Both projects were funded with incentives from local utilities, allowing the university to conserve dollars for actual implementation. For every recommendation made by the engineer, the client received a thorough lifecycle cost analysis to guide decision-making on future capital improvements.

In 2013, our firm conducted a project at Building A, a 240,000-sf biology lab facility built in the mid-1990s. Initial investigations revealed this building was using 43% more energy per square foot than another lab building on the campus that had been equipped with VAV air-handling units. In addition, Building A was using considerably more energy than a benchmark from the Labs21 database.


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Problems with lab energy efficiency may involve individual pieces of equipment, entire systems, small components (such as sensors) and/or controls. A quality retro-commissioning provider will assess functionality at all levels.  


The engineer ultimately identified 13 potential energy cost-reduction measures, with 11 recommended on the basis of their feasibility and ROI. Conversion of eight air-handling units to variable volume in four projects (two at a time) represented the largest potential annual energy savings, but also the longest payback period. Other projects, such as changes in VAV box scheduling and static pressure resets, were less expensive and offered a shorter simple payback—but also lower potential energy savings. Together, the 11 recommended measures provided an estimated reduction of nearly $790,000 on annual utility costs. Payback ranged from as little as a month, to as much as eight years. The university now has a useful planning tool for future investments in this lab building.

The university’s Building B was retro-commissioned in 2013-14. Built in the mid-2000s, this 330,000-sf facility comprises labs, offices and an auditorium. Our study resulted in development of seven energy cost-reduction measures—with the first ultimately split into two phases for budget purposes. Total identified annual cost savings were nearly $128,000 a year, with paybacks ranging from less than six months to more than 10 years.

The university placed a priority on a two-phase project to correct airflow-measuring devices that control supply and exhaust airflow for VAV boxes. The first phase of this work has already been completed, resulting in cost savings of more than $35,000 a year, with a simple payback of less than one year. Phase 2 will be scheduled when budget allows. A second measure, involving rescheduling of an air-handling unit serving the auditorium, has also been implemented, with annual cost savings of over $2,000 and a simple payback of less than six months. The university took a pass on other measures due to their long payback periods. The implemented projects not only saved energy, but also improved air quality and occupant comfort.

In conclusion, retro-commissioning is a powerful and cost-effective tool for increasing a lab’s sustainability, while reducing operating costs. RCx represents excellent financial and environmental stewardship, as reflected in the willingness of many utilities to underwrite the work. With the aid of an experienced RCx provider, you may find significant savings await discovery in your existing lab facilities.

John D. Villani, PE, is a VP at Grumman/Butkus Associates (G/BA) He directs the firm’s commissioning and retro- commissioning practice, including work by a branch office in the New York metropolitan area.

Daniel L. Doyle, PE, is chairman of G/BA and maintains an active engineering practice, with a particular emphasis on lab and healthcare facilities.