Retrocommissioning (RCx) is the process of ensuring that an existing building’s energy systems and equipment are operating at their optimal levels to meet the needs of the building’s owner and occupants. As a comprehensive process rather than a set of prescriptive measures, RCx addresses a building’s underlying system-level deficiencies rather than isolated quick-fix problems. Its benefits include an energy-efficient building that is operated and maintained by a well-trained staff or service provider, a comfortable and safe working environment for the occupants, and energy savings that will persist over time. Retrocommissioning can lower building operating costs in two ways: by reducing electric demand, energy consumption, and maintenance complaint calls and by increasing occupant comfort and equipment life. A 2004 study conducted by the Lawrence Berkeley National Laboratory showed that RCx is one of the most cost-effective means of improving energy savings in commercial buildings, with average whole-building energy savings of 15 percent and a simple payback of 0.7 years for building owners.
The Energy Use Index (EUI), the basic measure of a building’s energy performance, is the amount of energy in Btu consumed annually per square foot of conditioned space. It is calculated by tabulating all the energy consumed annually in a building and dividing that Btu measurement by the square footage of floor area that is heated, cooled, or both. Good candidates for RCx include buildings that have an unaccountably high EUI, an unexplained increase in energy consumption, or persistent occupant-comfort complaints. The U.S. Environmental Protection Agency (EPA) has published energy performance target ratings (48 KB PDF), a table of nationally averaged EUI values by building type. This table provides a quick initial assessment by which you can benchmark a building’s energy performance. A more comprehensive approach is to use the EPA’s free online energy-performance rating tool, Portfolio Manager, which takes into account source energy and the impact of weather variations as well as changes in the key physical and operating characteristics of each building. High utility costs and the availability of utility incentives, an experienced in-house staff, and high-quality building documentation are additional factors that can contribute to a successful and cost-effective RCx project.
Buildings with a majority of older equipment that will need to be replaced in two or three years are not good candidates for retrocommissioning—it would be more cost-effective to allocate RCx project funds to the future purchase of new equipment. Buildings with major system-design problems also make poor RCx candidates because efficiency improvements will never compensate for a serious system-design flaw.
The RCx process typically begins with the selection of a commissioning provider who will guide the project through the planning, investigation, implementation, and hand-off phases. A qualified provider will have excellent communication skills, be adept at cultivating a team approach to problem-solving, and be skilled at providing operations and maintenance (O&M) training. The provider will also need to have significant experience in building energy systems design, operations, and troubleshooting and to be well-versed in diagnostic testing, monitoring, and analysis techniques.
Certification of commissioning providers is currently offered by five independent organizations, each with its own unique standards, which can be viewed in detail on the company web sites (see sidebar). Building owners may or may not consider certification to be an important qualification for their commissioning provider. As or more important are the provider’s technical knowledge, relevant experience, and communication skills. Some building owners with significant in-house expertise—at the level of an energy manager or energy engineer—may not choose to involve a commissioning provider at the beginning of the project, but will bring one in later for specific diagnostic, monitoring, and analysis tasks. Once the commissioning provider has been selected, he or she will work closely with the building staff and follow a four-phase process.
Planning phase. In the planning phase, the building walk-through is an intensive information-gathering session that gives the commissioning provider the opportunity to talk with the operations staff, become familiar with the major energy-consuming systems, and begin to identify potential energy-saving measures (see sidebar). Prior to the walk-through, the building’s operations staff should prepare a prioritized list of existing problems and necessary improvements, along with insights on current building conditions. The owner should provide utility bills for the last three years, preventive maintenance records, and any active service contracts. All this information gives the commissioning provider an in-depth understanding of the building’s energy usage and O&M practices so that he can develop an accurate and realistic RCx plan that defines the project objectives, scope, schedule of procedures, and documentation requirements.
Investigation phase. The goals of the investigation phase are to understand how the building systems are working and to identify and prioritize energy-saving opportunities and system improvements. Start by assembling critical staff, both in-house and outside contractors; their knowledge of the building and its operations will be essential to conducting a successful RCx effort. A thorough review of building documentation and current O&M practices should then be undertaken by the commissioning provider, including the owner’s specific operating requirements, such as temperature and humidity setpoints, outside air requirements, and occupancy schedules.
Diagnostic monitoring comes next, measuring whole-building and end-use energy consumption, operating parameters such as actuator and damper positions, outside air-temperature and humidity levels, and equipment run times. Short-term diagnostic monitoring can be conducted using a building automation system’s trend-logging capability or with portable dataloggers. The measurements provide an understanding of the system’s performance under various operating conditions, which allows the provider to calculate potential savings opportunities and to identify problems that may require further investigation through the functional testing of individual equipment. This diagnostic monitoring forms the energy-use baseline against which all future energy-saving measures will be calculated.
The commissioning provider will discuss a list of findings with the owner, including identifying the most cost-effective energy-saving opportunities and the system improvements that are within the scope and budget of the project. Together the owner and the provider decide which strategies to implement, and the provider summarizes the recommendations in a report to the building owner.
Implementation phase. Depending upon in-house resources and time constraints, there are several approaches the building owner can take to implement the recommendations:
- The building owner hands the project off to the commissioning provider for full implementation of all recommendations.
- The commissioning provider is retained in an oversight role, providing assistance but conducting very little actual field work; the building owner retains responsibility for managing the work flow and contracts with various firms to carry out the implementation plan.
- An owner-led approach is appropriate for those who have significant in-house staff expertise or who have ongoing relationships with qualified service providers who can both manage and complete the project work.
The commissioning provider develops an implementation plan appropriate to the chosen management approach, incorporating milestones for documentation and verification of results as the project progresses. This plan organizes and defines the work needed to complete the savings and improvement measures. Upon completion of each measure, the system is tested and the data compared to the energy baseline. Calculations are performed to confirm that the expected improvements and resulting energy savings have been realized and that the measures are well integrated and are having the anticipated effect on the building.
Hand-off phase. In the project hand-off phase, the commissioning provider develops a comprehensive record of the entire RCx project that brings together all of the important information from project deliverables in a summary form. O&M manuals should be compiled for each energy-saving measure and system improvement as valuable resources for the building operations staff. The commissioning provider also conducts in-depth training to ensure that the staff has the skills to maintain the improvements and energy savings as well as to do any specific O&M functions required to sustain a high level of building performance. To achieve long-term persistence of the RCx effort, the commissioning provider recommends strategies, in the form of an ongoing commissioning plan, that the owner and operations staff can follow to confirm that savings are continuing into the future.
Retrocommissioning is an extensive undertaking that requires a significant commitment in time, effort, and funding by the building owner and operations staff. This process results in a building whose energy systems and equipment are operating at optimal levels and meeting the needs of the building’s owner and occupants. You can expect substantial savings that will persist over time and quick payback periods. Many utilities offer incentives for retrocommissioning, including paying for part or all of an initial RCx feasibility study or paying for a portion of the cost of implementation.