In the last few years, major cities throughout the country have passed new energy code requirements mandating that commercial buildings perform regular retrocommissioning audits. Austin, TX, now requires an energy audit prior to the sale of any commercial building, while San Francisco and New York require energy audits on commercial buildings over 10,000 sq ft every five years and buildings over 50,000 sq ft every 10 years, respectively.
Now, improving a building’s energy performance isn’t just the right thing to do — it’s required.
And rightfully so. Many of today’s commercial buildings aren’t operating or performing as intended. Brought to the attention of the building owner or operator by any number of red flags during daily or emergency operations, a building’s existing MEP systems can be retrocommissioned to perform optimally.
Problems in the Field
While retrocommissioning can help mitigate many daily operational issues, this article will focus on six of the most common problems found in the field: loss of utility power, hot and cold complaints, initial design or installation flaws, higher than anticipated energy costs, evolving business needs, and new energy directives.
Loss of utility power. It’s often not until there’s a real emergency, like a power outage, that the merits of a building’s MEP equipment are tested. Although individual pieces of MEP equipment were likely tested upon installation, it’s unlikely that full, integrated systems testing, like the “pull the plug” test, has been performed without formal commissioning. And just because a stand-alone piece of equipment will restart after a power loss doesn’t mean that it will integrate with the rest of the system as a whole when the utility returns.
This is a common problem for today’s commercial office buildings. During the equipment level commissioning of a large scale chiller plant, Syska Hennesy Group took each piece of equipment offline individually and restarted with success, but when the plug was pulled on the system as a whole, the chilled water system didn’t come back online in its original operating configuration as intended.
The Cx team went back in to manually put each piece of equipment online and discovered the underlying cause. Due to the large quantity of automatic transfer switches (ATSs) and excess data points monitored by them, by the time the programmable logic control (PLC) system recognized that all ATSs transferred to emergency power and the emergency power restart program should be initiated, a good portion of the equipment was locked out by the BMS. Instead, its redundant unit was put into operation, thus the system restarted with a configuration that was different than the original, prior to the loss of utility power.
During retroCx, a full systems test, including the “pull the plug” test, should be performed to simulate a true loss of utility power and confirm that all critical building systems restart again as intended without any issues.
Hot and cold complaints. Because buildings aren’t typically occupied in full on day one, if the MEP systems were not properly commissioned prior to being turned over to the owner, there is no certainty that they will be capable of meeting the design intent once the building is fully occupied. System loads and building systems operations vary based on occupancy and season, and often cannot be optimized until a building is fully occupied.
In another example, when a building is turned over during the winter months, the performance of the cooling systems cannot be tested unless a simulated load is induced, or seasonal testing is performed. The same applies to testing the heating systems during the summer months. Typically, this type of testing is only performed during a formal commissioning process.
Damper systems are another good example. Depending on specifics of the climate, outside air dampers left open beyond the fall or the spring will create an adverse heating or cooling response in the building, requiring the chillers or boilers to work harder to compensate for the unnecessary outside air in the space, possibly exceeding their rated capacity. Any and all of these likely scenarios can prompt hot and cold complaints from building occupants. When these complaints become a common occurrence, it’s time to reevaluate the MEP systems.
Additionally, over time, a wide range of changes can be made to the building’s HVAC system in response to hot and cold complaints, which can detune the system, throwing it out of whack. When a Cx agent goes back to re-verify the system and its controls as a whole, it’s possible to correct what was changed over the years and identify the root causes of these complaints.
Initial design and installation flaws. Without a third-party commissioning agent on board from day one of a new building’s initial design, design flaws may not be identified and resolved until installation or the building has experienced various operational phases. Some examples include: incorrectly locating thermostats on the design drawings; a pressure sensor not installed at the optimal location for a VAV system; valves installed backward in the field; under- or over-sized equipment that may also lack the proper redundancy to meet the owner’s expectations for the building.
In this case, retroCx provides a proactive approach to solving problems that no one knew existed, which can make the difference between a fully functional building and one that is flawed from day one.
Higher than anticipated energy costs. This red flag can be the first indication to building owners and operators that the energy efficient MEP equipment they installed isn’t living up to their expectations.
A variety of problems can be the cause. Night setback modes on the air handling units or occupancy sensors on the lighting system may not have been commissioned and properly integrated into the building management system (BMS). It’s also possible that someone working in the facility afterhours disabled the unoccupied mode, but forgot to turn it back on. Another example might be a leak in the ductwork that was originally sealed and tested, but now, years later, is causing a loss in static pressure and the VFD to operate at a higher frequency than intended to compensate for the loss of air. RetroCx goes back to examine the energy savings to make sure the systems are functioning per the building’s original design intent.
Business needs change. As businesses evolve, so do their office spaces. Oftentimes changes are made from an architectural perspective, but the mechanical impact of these changes isn’t reevaluated.
Office renovations may have resulted in open spaces being enclosed to create new cubicles or offices or similarly, walls may be knocked down where they previously existed. For example, three small offices originally designed for a maximum of six people were knocked down to build a conference room that can now hold as many as 15-20 people. Thermal comfort and IAQ issues could easily result. Therefore, anytime a major or even minor architectural renovation occurs, don’t forget to commission the corresponding MEP systems to suit the new condition.
New energy directives. Today’s corporations have new sustainability directives driven from the top down that tie the corporate message as an environmental steward with the real goal of saving energy. As a company’s business needs evolve, so might the MEP systems that serve the space the company’s employees occupy. RetroCx reevaluates the building’s current MEP usage to determine existing systems performance and cost effective retrofit opportunities for improved and even optimized performance.
Common and simple improvements include the addition of VFDs to significantly reduce fan energy consumption and costs and the installation of simple lighting controls, including responsive light fixtures and ballasts to enhance efficient lighting fixtures and lamps. This could be in the form of occupancy sensors for the light switches or daylight sensors to control the daylight.
The RetroCx Process
Once the building owner, operator, and Cx agent have identified their problems in the field that need to be solved through retroCx, it’s time to delve into the process itself. Beginning with a review of as-built documentation, the development of processes and procedures, the actual testing and the final report, understanding the retroCx process, and the owner and operator role in it will help make it a success.
Step 1: Review as-built documentation: As-built documentation is collected and reviewed thoroughly to give the retroCx agent an accurate understanding of how the existing MEP systems were originally intended to operate. This review will ensure that the operating staff has an accurate and complete set of as-built drawings. Include multiple operator staff interviews to get a real feel for how systems are currently operated and to help fill the gaps if there is a lack of documentation, ultimately creating a benchmark for the retroCx testing.
The retroCx agent will analyze field operations by examining the equipment itself and documenting its current set up, operations, and weak points. Operator interviews are the most important piece to this initial step, used to give the retroCx team an idea of what issues the building is currently experiencing, which issues surface routinely, and what type of systems and equipment training the staff is provided, drawing a “front lines” comparison from the building’s original design intent to today’s operations.
Step 2: Develop process and procedures: This step creates a list of procedures specific to the testing of each system and piece of equipment. This also includes planning for which systems can be tested during normal business hours and which systems will require after hours testing. In addition, all potential risks to the building operation need to be identified and backout procedures will be created when necessary.
During this step the retroCx team might ask themselves: What tests will be best for each system? When and how should the tests be performed? Which systems are interdependent and require coordination for testing and general set up? Issues of redundancy will be considered at this time as well. Which systems are supposed to be redundant and how is the testing going to affect that? The option to bring in a temporary system or false load for testing will be considered as well.
Step 3: TESTING! Throughout the testing of the systems and equipment, the retroCx team will determine if subsequent testing of a particular system or piece of equipment is necessary based on the initial results, while the primary goals of the retroCx will be championed. For example, if the goal of the retroCx is to gain more energy efficiency from the building’s systems then the tests will be designed around this goal. If redundancy is the goal, then testing will evaluate the coordination of the systems and their back up equipment.
Once the retroCx agent has verification that all the equipment is functioning on an equipment and systems level, an integrated “pull the plug” test will be performed, shutting down and restoring utility power to the building systems as a whole, while fully documenting how the building systems react.
Step 4: The RetroCx Report: Once the testing is complete, a retroCx report is issued to the facility’s owner/operator. This report will not only detail the level of results of all the testing, but will also provide recommendations to improve current conditions, including a rough magnitude of investment necessary to make the recommended changes. This will help owners prioritize, per their budget, which next steps can be taken. Syska Hennessy Group, when providing retroCx services, also includes additional issues or suggestions in the retroCx report that are beyond the goals set out initially by the owner to provide another level of potential recommendations for improvement as part of standard delivery.
With an understanding of the various operational problems in the field and how the retroCx process can help solve them, commercial building owners and operators can face their new local energy code requirements head on to bring a building’s performance right back to where it belongs.