Retrocommissioning (RCx) also referred to as Existing Building Commissioning (EBCx), has been available to building owners and managers for some 20 years. Arguably it is one of the most compelling and least understood strategies for managing building energy use.
The Building Commissioning Association provides perhaps the most comprehensive definition of EBCx: “Retrocommissioning is a systematic process for investigating, analyzing, and optimizing the performance of building systems through the identification and implementation of low/no cost and capital intensive Facility Improvement Measures and ensuring their continued performance.” Quantitatively, EBCx projects have been demonstrated to save 10-20 percent of a building’s annual utility spend at a simple payback of five months to 2.4 years .
The EBCx Process
The systematic EBCx process consists of four interdependent steps:
- Planning
- Investigating
- Implementing
- Verifying
To generate the greatest facility impact, the most important step in any energy management project is planning. Planning is critical to success because a well thought out and documented project plan invariably leads to more significant energy savings for the client. EBCx projects are no exception. It is the job of any building’s stakeholders (e.g. property managers, owners, executives, building engineers, consulting engineers, etc.) to come together as a team, select a commissioning authority and develop, communicate and document the EBCx project objectives.
The commissioning authority can be a qualified organization that specializes in EBCx or the building staff themselves. Regardless, the EBCx team must bring to the project specific knowledge of the building as well as industry experience in implementing the EBCx process. In the planning step, the team will review the existing building documentation (drawings, previous energy studies, etc.) and historical utility data. With objectives defined and initial building information discussed, the EBCx team documents a formal project plan with tasks, assigned resources, timeline with milestone dates, and budget.
Investigating opportunities for energy reduction is the next step. Though the EBCx project is principally designed to identify no and low-cost operational improvements, it is important for the team to fully document all facility improvement measures that require capital budget as part of the investigation step. Typically a senior engineer leads a support staff while identifying savings opportunities. Tasks may include trending energy use, temperatures, relative humidity, carbon dioxide concentration, etc. It is important to be able to provide reporting on energy usage at the equipment level, which may require sub-metering to be integrated to the Building Management System. The primary deliverable is an EBCx opportunity matrix that identifies a list of deficiencies (repairs) and potential improvements (FIMs). The client ultimately decides which opportunities to implement, which occurs in the next step. As a means of verifying improved performance, the commissioning authority will retest/retrend data as identified in the EBCx plan and make updates to the EBCx opportunity matrix.
The final phase of a properly executed EBCx project is the Hand Off, which usually consists of the delivery of the final commissioning report, including revised control sequences and other related building documentation, training of pertinent building staff, including the operations and maintenance engineers, and development of a performance tracking plan to ensure energy savings continue as commissioned.
An effective solution for tracking performance is Monitoring-Based Commissioning (MBCx) which provides the functionality for the commissioning authority to remotely access the building management system to monitor and report on adherence to the revised control strategies. By providing proactive monitoring, the risk of drifting out of control is minimized, protecting the facility investments in the EBCx improvements and ensuring the planned energy savings.
Rate of Return greater than or equal to 100 percent
A compelling argument for commissioning is the recent work completed by Lawrence Berkeley National Laboratories. In the report “Building commissioning: a golden opportunity for reducing energy costs and greenhouse gas emissions in the United States ,” author Evan Mills presents the world’s largest compilation and meta-analysis of commissioning experience and the associated literature, comprising 643 non-residential buildings, 99 million sq. ft of floor space, $43 million in commissioning expenditures, and the work of 37 commissioning providers.
The median normalized cost to deliver commissioning is $0.30/sq. ft. (2009 currencies) for existing buildings. The one third of projects for which data are available reveal a total of more than 10,000 energy-related deficiencies, the correction of which resulted in 16 percent median whole building energy savings in existing buildings with payback times of 1.1 years. That represents a nearly 100 percent rate of financial return, an excellent prescription for returning a building to functional and financial health
