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Want a better building? Do this.


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by Justin D’Arcy, PE, and Sumeta Sachdeva, WELL AP, LEED BD+C

Approximately two thirds of the building area that exists today will exist thirty years from now, according to Architecture2030. Why not save money, energy, and establish a baseline for future projects on your existing buildings? Two options are Energy Audits (ASHRAE Standard 211-2018) and Existing Building Commissioning (ASHRAE Guideline 0.2-2015). If you’re an owner, or helping an owner with solutions, what’s the difference between them—and how do you decide between the two?

Existing Building Commissioning

Existing-Building Commissioning (EBCx) is a process to identify and implement opportunities for energy savings as well as facility improvement recommendations, usually focusing on the HVAC systems of the building. EBCx is made up of 5 phases: planning, initial assessment, investigation, implementation and handoff. The bulk of the time on the job site by the commissioning provider (CxP) is typically spent in the planning and investigation phases although each phase is critical to ensure project success. EBCx recommendations are often no-cost/low-cost measures and can be easily implemented by CxPs the building owner already has on call, such as the building automation system controls contractor. The owner is likely to be actively engaged with the implementation process and the CxP is responsible to commission and verify implementation of the improvement measures.

Energy Audit

An energy audit can be thought of as a wider breadth application of the planning and investigation phases of EBCx. ASHRAE Standard 211 is the new standard, effective in May 2018, for commercial building energy audits. There are three (3) levels of energy audits detailed in this standard – Level 1, Level 2, and Level 3. Level 1 is the most basic energy audit which includes a brief walk through of the facility, an overall assessment of energy performance, and identification of no-cost and low-cost energy efficiency measures (EEMs).

Level 2 takes a few steps further with added detail on the site survey and additional information in the report related to HVAC, building envelope, lighting, plug loads, etc. Additional analysis is conducted on cost impacts of the recommended EEMs with a thorough analysis. This second level also provides a more in-depth utility analysis with a breakdown of energy use by end-type. Level 3 incorporates everything from Levels 1 and 2, and is the most comprehensive audit. The third level requires either sub-metering of equipment or energy modeling to calculate the savings for the EEMs and capital investments recommended to the owner, providing the most comprehensive analysis of existing building conditions and recommended measures.

Considerations for Making the Decision

EBCx. One of the great aspects of EBCx is a relatively short timeline, typically six to twelve months, from start through verification and energy savings. Savings typically ranges between 3% (25th percentile) to 10% (75th percentile) with a median savings of 6%, based on the 2018 Value of Commissioning Market and Building Data Survey by the Building Commissioning Association and Lawrence Berkeley National Laboratory.

Unlike an energy audit, EBCx includes an implementation and verification phase in which the no-cost/low-cost recommendations are executed and verified. This can be very helpful to ensure no loss of momentum in the project from discovery of these opportunities to acting on them.

Energy Audit. An energy audit takes a holistic and thorough approach to the current building condition and equipment performance. Items like building envelope, utility rate structures, benchmarking, energy modeling and sub-metering are given more of a focus in an energy audit when compared with EBCx. Additionally, energy audits place a greater focus on capital measures and items with a long payback such as a chiller replacement project helping to create a long-term plan.

In general, we would recommend an energy audit for the owner who wants to gain a long term and encompassing plan on how their building currently operates and how it can be improved, with a greater focus on capital improvement ideas, along with limited- to no-commitment on any immediate implementation of improvement recommendations or upgrades. An energy audit would also be more suitable for a building with no building automation system as it limits large controls-related savings opportunities for typical EBCx projects. In contrast, we would recommend EBCx for the owner who intends to pursue implementation and wants assistance to ensure potential savings are realized and verified.

Compared Outcomes

There are more similarities than differences when comparing the two. Both services provide no-cost/low-cost energy efficiency recommendations to the owner, provide at least a basic summary of the current building operation/condition and a minimum twelve-month utility analysis. Both project types involve job site visits, interviews with the owner and operations staff, and data collection. Energy savings calculations and cost estimates are a focus of both services, which are instrumental in determining which recommendations to move forward with.

Regardless of which option an owner chooses to pursue, the service provider will typically review the recommendations with the owner to answer questions, discuss potential challenges, and plan a potential timeline.

Either option will leave the owner with a path forward to a better and more energy efficient building. However, for maximum short- and long-term gains, owners are encouraged to take a hybrid approach to incorporate both EBCx for short term improvements and savings along with an energy audit to provide the roadmap to long term improvements and energy efficiency.

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