Retro-Commissioning: Big Energy Savings For Big Buildings

The Architect of the Capitol's (AOC) commitment to energy conservation and sustainability has resulted in a reduction of energy use by almost 50 percent across the Capitol campus since 2003. The agency continues to look for ways to build on those efforts as it works toward achieving reductions beyond the 50 percent goal by 2025. The AOC focuses energy conservation and sustainability efforts on building systems throughout its portfolio to positively impact building ventilation, thermal comfort, material selection, construction practices and maintenance material usage. Maintaining an enterprisewide focus on energy conservation has helped make our buildings more efficient and sustainable.

As part of this comprehensive energy conservation program, the Energy and Sustainability group is undertaking retro-commissioning of several buildings on the Capitol campus to enhance the energy performance of those buildings.

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Retro-commissioning improves the efficiency of an existing building's equipment and systems. This process can often resolve problems that have occurred during design or construction, or as in the AOC's case, address problems that have developed in the building as equipment has aged or as building usage has changed. Retro-commissioning involves a systemic evaluation of opportunities to optimize energy-consuming systems and improve a building's operations and maintenance procedures to enhance overall building performance.

Our Process

The AOC uses retro-commissioning to periodically retune our buildings and return them to peak efficiency. The continued focus on energy conservation results in utility cost savings that are reinvested into our buildings and infrastructure. These investments have resulted in reduced long-term energy demand and reduced greenhouse gas emissions across the Capitol campus.

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Electronics Technician Edward Williams and A/C Equipment Mechanic Justin Zibragos discuss an air handling unit’s operations using the AOC's Building Automation System graphics platform.

Over the last 15 years the AOC has reduced its energy intensity level by almost 50 percent. As a result of these energy savings, the AOC's building-related greenhouse gas emissions have been reduced by over 48 percent.

The Energy and Sustainability group currently tracks the steam, chilled water and electrical performance of individual buildings throughout the Capitol campus. As part of this process, energy performance target metrics are developed for each building. The Energy and Sustainability group compares weekly and monthly usage against those targets to determine how a particular building is performing. This information is shared with the energy and facilities managers across the AOC. If a building is exceeding the established targets for steam and chilled water energy consumption it is a potential candidate for retro-commissioning.

Our Projects

Through this consistent monitoring, the Energy and Sustainability group has identified several buildings on the Capitol campus that are exceeding the established energy targets for steam and chilled water. The steam and chilled water components are directly related to the HVAC systems in each building. In part, the increase in HVAC consumption can be attributed to operations during the COVID-19 pandemic. However, the Energy and Sustainability group, along with AOC energy and facility managers, want to ensure that the HVAC systems are performing optimally given the new operating requirements, hence the need to undergo HVAC system retro-commissioning.

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A/C Equipment Mechanic Anthony Mungal replaces a malfunctioning chilled water valve actuator, while Justin Zibragos assists by steadying the ladder.

Retro-commissioning can help improve a building's operation and maintenance procedures by identifying and correcting problems, such as:

• Equipment that is operating when it may not be needed
• Systems that are simultaneously heating and cooling the same spaces
• Belts and valves that are malfunctioning
• Thermostats and sensors that are out of calibration
• Air balancing systems that are less than optimal

Many of these small operations and control improvements cost little or nothing to implement yet can have big energy saving impacts. As an example, sensor calibration not only improves current operations but also increases the effectiveness of diagnostic monitoring and testing.

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A/C Equipment Mechanic Justin Zibragos tests temperature sensor function using an electrical tester.

The current scope of the project is to retro-commission the HVAC systems in the Rayburn and Longworth House Office Buildings and the Dirksen and Russell Senate Office Buildings as well as the U.S. Capitol Visitor Center. The Energy and Sustainability group will continue to evaluate energy performance of Capitol campus buildings and plans on retro-commissioning additional buildings in future years.

The Benefits

Retro-commissioning not only benefits the AOC by reducing operating costs through energy savings and improving equipment performance, but it also improves tenant experience. Building tenants will be more comfortable because adjustments lead to more consistent temperature control and better indoor air quality. Additionally, energy and facility managers will face fewer tenant calls and will be able to stay focused on managing building systems.

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A/C Equipment Mechanic Kerian Ozurumba takes airflow readings from a vent using a balometer.

Retro-commissioning can produce significant cost savings in buildings, but the savings can vary depending on the size, age of equipment and the scope of the effort. In general, by undertaking this retro-commissioning effort, the AOC can conservatively expect to have a payback period of less than two years and an energy savings of 5 to 10 percent. Since the current retro-commissioning projects are focused on the correction of operations and control measures, savings are anticipated to exceed these payback and energy saving estimates.

Retro-commissioning is an important tool in helping the AOC achieve the established 50 percent energy reduction goal by 2025 and supporting jurisdiction goals of creating comfortable spaces for building tenants. This process will continue to be used periodically on all Capitol campus facilities to ensure that systems are operating as efficiently as possible.