Retro-commissioning (RCx)

“Retro-commissioning” (RCx) is a cost-effective and systematic process to regularly review the performance of existing buildings and identify potential operational enhancements that can help save energy and reduce energy costs. It involves a single piece of equipment or bunches of systems constituting a large-scale retrofit project.

The retro-commissioning process involves several steps, including a building assessment to identify areas for improvement, develop a plan to address those areas, implement the improvement works, and ongoing monitoring and verification to ensure the desired results. The process may involve building automation, lighting, HVAC, and other building system upgrades.

The benefits of retro-commissioning can reduce energy consumption and costs, improve indoor air quality, increase occupant comfort, and extend equipment life. In addition, retro-commissioning can help building owners and managers comply with local energy codes and regulations and achieve sustainability goals.

Terminology

The APEC member economies have different terminologies representing commissioning or retro-commission-related processes. This section shortlists some terminologies used in APEC member economies with similar objectives or processes adopted in this project. The following table summarises these terminologies.

The terms Existing Building Commissioning, Retro-commissioning (RCx), Building Tuning and Continuous Commissioning involves verification, optimisation, and analysis of existing equipment to identify efficiency and cost savings, which are similar.

Ongoing Commissioning is a continuous process that helps monitor and ensure effective and efficient building performance over its lifecycle (16). Energy use, benchmarking, conformance to and continuous revision of the current facility requirements, automated fault detection and diagnostics, and training are all key parts of the ongoing commissioning process.

Re-commissioning, it is the commissioning of existing buildings and systems that have already gone through the commissioning (1)(3) or retro-commissioning (11) process. The building will become less efficient over time and increase the overall operating expenses. Hence re-commissioning aims to bring a building back to the original design criteria, maintain top levels of building performance, and identify new improvement opportunities. This process is for operational buildings needing minor repairs, replacements, and resets.

The building operating and maintenance systems are examined and cleaned as needed during the commissioning process, parts may be fixed or replaced, and systems reset as if they are being installed new. This can provide the opportunity to strategically and effectively revitalize an older building. It allows a continuous building operation without losing comfort or energy efficiency.

Moreover, some terminologies used in the APEC member economies consist of “commissioning” but for new buildings, which are not the focus of this study. As summarised in table below, the terms Commissioning, New Construction Commissioning, Building Commissioning and Initial Commissioning have similar meanings, i.e. the process involves commissioning new buildings and newly installed equipment for proper operation. The record of the results is an essential reference during subsequent recommissioning (17).

Processes of RCx

Retro-commissioning (RCx) is a process that involves evaluating and optimizing the performance of building services and even the building envelope of existing buildings to improve their energy efficiency, indoor air quality, and overall comfort.

Here is an overview of how retro-commissioning works:

1. Benchmarking: The first step is to benchmark the building's energy usage and performance. This stage involves gathering data on the building's energy consumption, indoor air quality, and other key performance metrics.
2. Assessment: A comprehensive assessment of the building systems, including HVAC, lighting and controls, will be conducted. The opportunities to optimize performance, as well as energy and cost savings, will be identified. In some cases, recommendations for capital improvements may result in the assessment. They will be outside the scope of the retro-commissioning work.
3. Analysis: The assessment team will use the data and information gathered during the assessment to analyze the building's systems and identify opportunities for improvement. The stage may involve identifying equipment not operating as efficiently as it should be, fixing leaks or other issues, or upgrading to more energy-efficient equipment.
4. Implementation: After the analysis, the assessment team will develop a plan to implement the recommended improvements. This stage may involve changing the building's systems, such as adjusting heating and cooling settings, upgrading equipment, or installing new controls.
5. Monitoring: After the improvements have been implemented, the assessment team will monitor the building's performance to ensure that the changes have led to the desired outcomes. They may also train building operators and occupants and help them maintain the building's new level of performance. This hand-off may be a transition to Ongoing Commissioning.

For items (i), (ii), (iii) and (v), the works shall be mainly responsible by the RCx services providers, while for the item (iv) shall be decided by the building owner. Therefore, RCx is a process that requires different parties to collaborate and implement.

Benefits of RCx

Retro-commissioning can provide a range of benefits beyond energy efficiency that can help to improve the overall performance, comfort and safety of a building. Details are below.

1. Improved energy efficiency: Retro-commissioning involves comprehensively evaluating of a building's systems and equipment to identify inefficiencies, faults, and operational issues. These issues include malfunctioning equipment, poor control sequences, and outdated systems. By identifying energy-saving opportunities and fixing the malfunctioning or poor-performance parts, retro-commissioning can improve energy efficiency. Retro-commissioning involves ongoing monitoring and optimization of a building's performance to ensure that energy savings are maintained over time and even during low-load periods. Improved Indoor Air Quality: Retro-commissioning can identify and address issues with ventilation, air distribution, and humidity control, which can all have a significant impact on indoor air quality. By improving these factors, retro-commissioning can create a more comfortable and healthy indoor environment for building occupants.
2. Extended Equipment Life: By identifying and addressing issues with equipment that may be causing it to work harder than necessary, retro-commissioning can help to extend the equipment life, reduce maintenance costs and avoid premature replacement of equipment.
3. Increased Occupant Comfort: Retro-commissioning can identify and address issues with temperature control, lighting, and other factors impacting occupant comfort. Retro-commissioning can improve occupant satisfaction and productivity by creating a more comfortable indoor environment.
4. Compliance with Building Codes and Standards: Retro-commissioning can help to ensure that a building complies with current building codes and standards. This helps to avoid penalties or fines for non-compliance and ensures the building is safe and functional.
5. Improved Resilience: Retro-commissioning can also help to improve a building's resilience to power outages and other disruptions by identifying backup power sources and other measures that can help to maintain critical building functions during an emergency.