Sustainability and high performance buildings have become almost synonymous with energy efficiency as more building owners are trying to do the right thing while saving money. When deciding how to make your existing building more sustainable, it can be daunting to know where to start. Energy conservation is often a valuable beginning, as up to 20 percent of energy consumed in commercial buildings is wasted.1 There are a few energy conservation approaches used for different purposes, depending on your facility’s needs and goals. In addition to choosing an approach, you must also be able to justify the decision economically in your business framework. You may have already started working on some no- to low-cost initiatives that helped you improve, or perhaps you have already invested quite a lot of capital to help your building achieve energy efficiency. How can you continue to improve and pick an energy conservation approach which applies best to your situation?
Defining Conservation Approaches
The three most common energy conservation approaches are commissioning, energy audits, and building re-tuning. Each have their own distinctive characteristics that are applicable to some circumstances more than others. After explaining how each of them works, they will be compared and contrasted so that you may get a clearer picture and narrow down which one suits your current needs best.
Note: Facility Engineering Associates will be conducting a complimentary Building Re-tuning webinar as part of its FEA-U program on September 14, 2015, at 11 AM EDT. If you are interested, please contact Mayra Portalatin firstname.lastname@example.org to register.
It is essential first to gain a sufficient understanding of the intent of the aforementioned approaches. Commissioning is a formal process, typically conducted by a third party, who tests building systems to verify that they are operating as planned and according to requirements. If they are not, there is opportunity for potential energy savings. Commissioning is a broad term that frequently is applied to new construction, from the planning phase through initiation and beyond. This article is focused on existing buildings, so is often re-termed as retro-commissioning. Retro-commissioning is performed on a building that has not been previously commissioned. If the building has been previously commissioned, it is called re-commissioning.
Energy audits are usually performed by a third party as well. During an energy audit, the auditor conducts a walk-through of the building and identifies opportunities for energy and cost savings. The auditor will then make recommendations for improvement. The energy conservation measures can then be tailored to budgets, energy-saving goals, or how much you plan to accomplish. This scope can range from simple adjustments, such as modifying thermostat settings, to capital project development, updating large pieces of HVAC equipment.
Building re-tuning is a fairly new term that describes the process of continually correcting underlying issues in the building’s operation by inspecting its components, trending available data, and analyzing occupant responses. The outcome of this is more effective operation — leading to lower energy usage and cost, and improved occupant comfort. It can be performed by a third party, which would stimulate the maintenance group to work towards continual optimization, and then may subsequently be taken over by a facility manager or other in-house personnel.
Now that commissioning, energy audits, and building re-tuning have been defined, their most influential factors in making an appropriate decision can be compared. Table 1 below provides a comparison of these approaches. A prominent question is, “which approach will save the most energy and, consequently, money?” All three approaches can reduce energy usage, typically 5 to 20 percent, depending on the situation. Each approach can also help you attain a deeper understanding of your facility and its inner workings to benefit in the present and future.
Perhaps just as significant as saving money is how much one must invest to get there. Generally, the more comprehensive the evaluation is, the more it will cost. Thus, commissioning is the most expensive ($0.27 to $0.45 per square foot), and building re-tuning the least (as little as no cost)2 . Energy audits fall somewhere in the middle ($0.08 to $0.24 per square foot), depending on the desired degree of depth.
Another question regards required time and effort. Because commissioning is so involved, the process can take the longest, around 2 to 6 months. Energy audits can be expected to be completed in 3 to 6 weeks, conditional on extent. Building re-tuning can be finished in a single day, though the overall effort is ongoing. Both building re-tuning and commissioning are incorporated into ongoing programs, meaning they should be maintained even as the initial evaluation draws to a close. Energy audits (as well as commissioning) are recommended to be performed every 3 to 5 years.
Based on cost and time alone, the obvious choice seems to be building re-tuning. However, this is not always the best option. For this reason, one must also consider what each approach can provide in terms of scope. Commissioning tends to focus in maximizing efficiency of HVAC and controls. All of the energy-consuming systems and equipment in a facility are identified, then tested and compared to current goals. It functions as a type of preventative maintenance, detecting problems early on rather than after it is too late.
Energy audits offer options of three levels, each growing more involved: a walk-through analysis (I), an energy survey and engineering analysis (II), and a detailed analysis of capital-intensive modifications (III). Frequently, a Level II assessment provides a sufficient level of detail for capital planning. You may elect to conduct a Level I or II audit, assessing necessity of a Level III audit upon conclusion to further develop specific projects.
In building re-tuning, emphasis is put on small, quick, low-cost modifications, made on an ongoing basis. A building automation system (BAS) can be particularly advantageous in acquiring useful data to aid in discovering where problems lie, which may require the use of outside help to maximize its data usage. Building re-tuning can also be performed without a BAS.
Choosing an Appropriate Approach
Having learned the similarities and differences among the approaches, you are ready to make a decision. Ask yourself the following questions as they pertain to your organization:
- What is my budget?
- How much time is available?
- What do I want to accomplish overall?
The responses frame a context that steers you in the direction of an ideal approach. Figure 1 above helps you easily visualize what the approaches have in common with one another, and which aspects are unique. With these thoughts in mind, consider the following additional situations for which each approach is preferable:
- Large buildings or complex systems
- Not previously commissioned
- New facility manager (FM) with different expectations
- Any other major changes (in utility, occupant, BAS, etc.)
- Fine tuning desired
- Any commercial, institutional, or multi-residential facility
- Uncertainty of investment commitment
- List of recommendations desired
- In-house FM
- Limited budget
- Immediate changes desired
This list provides a number of example cases, but is not exhaustive. Each approach has different functions and intentions, but all have the ability to save energy and help to familiarize yourself with your facility.
Making the Business Case
Selecting a suitable energy conservation approach is only the first step to implementation. It must then be approved by management, requiring convincing justification. Sustainability is a valid pursuit, and it helps immensely to prove how energy conservation measures will affect the bottom line. What you prove is dependent on your driving goal, whether it be energy or cost savings. From a financial perspective, one would typically be interested in the payback period. The payback period using these approaches ranges among the methods and certainly depends on the significance of the findings. For example, readjusting occupancy sensors provides near instant payback, while replacing an old furnace will have a higher up-front cost and longer payback time. If you are focusing on cost savings, decide ahead of time which kinds of measures you prefer to implement and can afford, and base the approach type accordingly. On the other hand, if your target is energy savings (especially with a deadline), you may want to go ahead and replace that furnace if the energy savings are significant, with less concern about the long run.
Through knowledgeable and conscientious planning, you will be able to effectively implement the energy conservation approach that is the best fit for your organization. As your facility and its needs change, you may consider reevaluating using the same or different approaches. Successfully executing your chosen methodology will put your building on track to becoming an outstanding example to similar facilities in energy conservation and sustainability while saving you money.
Sara Ambry is a Staff Engineer at Facility Engineering Associates. She has a background in architectural engineering and works under the facility consulting services line that specializes in facility asset management, building energy management, and sustainability services.
1 Roskoski, Maureen K., Conrad Kelso, Brian Gilligan, and Lisa Shulock. “Building Re-Tuning: The Two Day ROI.” IFMA Facility Fusion. Rosen Shingle Creek, Orlando. 23 Apr. 2015. Feapc.com. Web. 14 Aug. 2015.
2 Hughel, Gregory J. “Commissioning vs. Energy Audits: Making the Best Choice for Your Facility?” Facility Facts 17 (Summer 2009): 1. Feapc.com. Facility Engineering Associates. Web. 14 Aug. 2015.