Commissioning Strategies for Campus Facilities
- By Michael Della Barba
- May 1st, 2009
Building commissioning is now well established as a quality assurance tool to deliver performance, reliability, and efficiency in new building systems. The LEED rating system, currently the nationally accepted benchmark for the design, construction, and operation of high-performance green buildings, recognizes the value of commissioning across all rating categories and has documented 100 percent recovery of commissioning costs very early in the design/construction process. So what does this say about existing building stock? If LEED states that commissioning is the key to acquiring a building that performs as intended, what about building systems that were never commissioned? Short of a substantial system failure, can we assume optimal performance? The answer is absolutely not. Performance verification requires a method of measurement.
If a third-party engineer commissions a building, as a commissioning agent I know a few things about the building. Let’s assume a building that’s approximately 200,000 sq. ft. in size.
- 150 to 200 components were reviewed, verified, and documented to design
- At least 200 to 300 deviations from the design were discovered
- 50 percent of the systems failed to reach design performance parameters when functionally tested
And if the building was not commissioned, I know:
- Systems are under-performing
- Operational problems exist
- Energy is being wasted
Am I assuming poor design, manufacture, construction, or operation? No, and that’s the point! Assume nothing. Operation can be physically verified, but performance needs to be measured. Operation does not necessarily equate to performance.
Energy Savings: A Result of Performance
The process of measuring and optimizing building system performance in existing buildings is often called re-commissioning, or more properly, retro-commissioning, if no commissioning was performed initially. Due to the complexity of commercial building HVAC systems, they are the perfect targets for performance assessments. Documenting that the HVAC system is meeting the designed performance standards and the resulting energy use is the only way to ensure efficient system performance. Studies (and our own experience) have shown that existing buildings present energy savings upwards of 25 percent, while reconciling mechanical system performance shortfalls, occupant comfort issues, and potential indoor air quality (IAQ) issues. The key to identifying these lost savings, and developing a plan to capture them, is a measurement plan based on real-time system operational data — retro-commissioning.
Colleges and universities today have motivation from two drivers to improve the energy efficiency of campus buildings. Energy costs are rising in an uncertain economic climate, and most are concurrently developing campus sustainability programs with a goal of dramatically reducing their carbon footprint. The built environment for most non-commuter institutions represents approximately 80 percent of the energy use for the campus, so a focus on building energy management is very appropriate. As a result, most campuses have already initiated lighting retrofits, insulation and window replacements, and behavioral changes to minimize energy consumption. However, when faced with developing an appropriate strategy for the all-important building systems, many campuses fail to measure and assess the performance of existing systems, and thus fail to address the underlying causes of poor performance prior to replacing “inefficient” capital equipment. This can often be a costly oversight, and significantly reduce the ROI potential of the capital investment while leaving deficiencies in place.
Fire, Ready, Aim
Without an initial commissioning process, we know that in all likelihood the building is not performing efficiently. Therefore, while replacing expensive capital equipment with more efficient equipment will reduce the energy being used, the existing equipment may be over-used in the first place. In many cases, the efficiency gain (and energy saved) from the new equipment will be less than the efficiency gained (and energy saved) from optimizing the performance of the original equipment. And the service life of the new equipment will be shortened by the inefficiency as well.
We uncovered an example of this recently during a retro-commissioning project on a building with an above-average energy consumption profile based on similar buildings. Two 100-hp. chilled water pumps were found ramping up in the middle of the night (in December in the northeast). This was traced to a modification made years before to alleviate a problem that no longer existed, and since this was occurring during unoccupied hours, nobody was aware of it. Through a no-cost modification, the unintended use of these pumps was eliminated entirely (and the energy required to run them) for eight hours/day from November through March. Had an equipment upgrade to more efficient motors been the only action taken, an energy reduction would’ve resulted, but a substantial amount of energy would still be wasted compared to the no-cost modification. And the new motors would be subjected to the same overuse, resulting in a shortened life. This is not a very sustainable strategy since it leaves in place a substantial amount of underlying inefficiencies that continue to waste energy and degrade performance, yet it continues to be a very common one.
Campus Energy Reduction Using Retro-Commissioning
While the retro-commissioning process can reduce the energy consumption of any building (that hasn’t been recently commissioned), it makes sense to prioritize the process and focus on the most likely targets. Using available characteristics (size, year built, use, and complaint log) along with any energy data that might be available at the building level, the focus of any effort can be narrowed substantially to a small set of prime targets. These buildings are then retro-commissioned using a three-phased approach that is designed to maximize the ROI of all improvement efforts.
Develop a building system performance profile.
This initial phase identifies the system(s) to be optimized, documents all associated equipment, and reviews the system control sequences. This creates a baseline against which all test results are compared. Once the building’s current profile is documented, systems data is collected over a defined length of time to create an actual building performance profile.
This phase additionally involves defining the building’s optimal operating strategy by analyzing the collected trend and metered data. The data analysis will focus on key factors such as temperature, equipment power draw, and run time, with an eye on operating issues, including equipment cycling and "off hour" operation. Deficiencies or system anomalies found are based on this actual performance data as compared to the building system’s optimal operating strategy.
This phase typically identifies some low- or no-cost actions to improve performance, as well as issues that require some engineering investigation to further refine. A 10 percent reduction in energy consumption is typically seen from actions taken during Phase 1. These initial savings can often be a funding source for additional energy-reduction efforts.
Perform engineering investigation and make recommendations.
This phase involves a more detailed engineering investigation and recommendations for improvement for more complex deficiencies. Here, the engineer works with the facility manager and operations staff to select specific items to undergo further investigation and engineering. Information from Phase 1 may suggest that inefficiencies exist in specific building systems, but the engineering investigation is necessary to finally determine the actual situation.
Correct deficiencies, analyze results, and recommend capital improvements.
The final phase involves prioritization and correction of those equipment and system deficiencies that the facilities group selects. A facility retro-commissioning project can be prioritized at this point to target individual zones, systems, or the entire building based on the projected ROI of the proposed improvements. The key to successful retro-commissioning is real-time equipment performance data as a tangible product from which these operational conclusions can be drawn.
A Strategic Optimization Approach
The retro-commissioning process encourages a strategic approach to building energy reduction that focuses first on optimization with the realization that energy savings are a natural result of performance. Thus, retro-commissioning initially focuses on optimizing the performance of the equipment and systems in place — not simply on replacement. Issues such as upgrading to more efficient equipment and systems can certainly be a recommendation resulting from the performance analysis, but should be treated as a separate action. Many of the action items targeted will be of the low cost variety (e.g., control set point changes, sequence improvements, and unscheduled operation identification) that will increase operational efficiency and create a short payback period for the retro-commissioning effort. A well-organized plan, clear system operating intent (benchmark for comparison), and a focused analysis will all contribute to minimizing costs while delivering the maximum return on energy investment to the institution.
Michael Della Barba is the director of Commissioning Services at Environmental Health & Engineering (EH&E), Needham, MA. He has extensive construction project management experience, including private, public, and institutional projects. Contact Della Barba at firstname.lastname@example.org or visit www.eheinc.com.