When commissioning a high-performance building, one element of lighting control is sometimes left out: the daylight harvesting system. It’s assumed such systems will work right out of the box after some simple calibration. Working is one thing, but working optimally is another. The full potential of daylighting (DL) can only be captured by commissioning the system controls and recognizing the influence made by other building systems, the building architecture and the space interiors.
In the 2013 research study, “Commissioning for Optimal Savings from Daylight Controls,” the Energy Center of Wisconsin’s (ECW) authors write, “While considerable effort is often expended in the architectural and lighting design of DL control strategies, the actual execution of the controls is an area for substantial improvement.”
The ECW findings suggest a need for significant calibration and commissioning efforts both during and after construction as DL controls “fall well short of optimal” after field calibration and startup procedures, according to the report.
In the study, ECW measured, in subhourly increments, the illuminance, lighting power, and heating/cooling data for systems in 20 office and other public spaces in Minnesota and Wisconsin. Measurements of the controls were taken and then repeated after they were commissioned. As a result, median lighting energy savings increased from 23 percent to 63 percent or 1,976 kilowatt-hours (kWh) for each kilowatt of lighting controlled.
Scott Hackel, P.E., LEED AP, senior energy engineer at the ECW, co-authored the report with ECW’s Scott Schuetter. Both also served as researchers.
“Lighting design now includes control systems that feature occupancy sensors, time clocks and daylight harvesting,” Hackel said. “It has come a long way. Unfortunately, the daylighting portion often gets shortchanged with little follow-through for these controls. While 30–40 percent of the systems we tested were operating well, many were not calibrated or initially commissioned. They were not fully executed to perform well.”
Researchers identified several elements they said needed to be formalized in a commissioning process. They included establishing illuminance targets; reviewing design documents for component location, orientation and sequence; functional testing of controls (including tuning); and verifying that proper owner training has occurred.
In new construction or major renovation projects, ECW researchers discovered the most critical steps in the commissioning process for DL control occurred after installation. Once the installation was verified, the system is calibrated, and functional testing is completed.
“We conducted basic startup tasks including tuning/calibration, shielding, redirecting sensors, connecting disconnected systems, changing timing settings and [making] other adjustments,” Hackel said. “All of these represented what we describe as a commissioning of a daylight harvesting system after install. We did discover systems that were maybe too complex when handed over to the installer or building engineer, which likely hindered for them an understanding of what was needed for such systems.”
Don’t leave savings on the table
One control element benefiting from commissioning was the sensor gain. It required measuring foot-candle levels twice during the day and then running a calibration to ensure light levels were where they should be for optimum performance. Hackel said that, without calibration, sensors might be set too dark, resulting in lights running brighter than needed, which you might not notice on a sunny day.
“Either way, you are wasting energy by running more foot-candles than you need and really defeating the purpose of achieving energy savings through a daylight harvesting approach,” Hackel said.
Calibration also differs based on the DL control system type.
“Some calibration occurs in hardware, at the fixture, sensor, controller or lighting control panel. We’ve run into calibration settings within all four areas. Some calibration occurs in software, which is either on a screen near the lighting control panel or networked to [a] connected device such as a laptop, tablet or even a smartphone. Hardware calibration is pretty easy, involving the adjustment of one or two knobs or switches. If it’s on software, it can vary from simple to very complex. Software is where the manufacturer is a great source for information and where training is really important,” he said.
The influence of other building elements
Building design will influence the effective performance of the harvesting controls when conducting daylighting commissioning (DLCx), according to Joseph J. Deringer, AIA, LEED AP, president of Building Science Analytics LLC, Berkeley, Calif.
“System monitors, controls and their placement typically are the focal point in standards, codes and green certification, but not all building elements that influence system performance are considered,” Deringer said, adding that a number of influences included divided building orientation, placement of windows, interior walls, doors, ceiling height, shading, skylights, even furniture placement, wall color and texture. Changes in these elements will disrupt daylight harvesting system performance.
“For example, a typical daylight harvesting system will be designed assuming a white surface with large light reflectance,” he said. “An interior designer who loves blues and dark grays might come in and specify those colors for walls, thereby reducing their reflectance. If you change any of the features that contribute to a workable DL system, you change its performance. DL systems can go awry in many ways.”
“In our study, missed calibration, improper zoning, heavy internal shading and improper relay connection all contributed to lower controls performance,” Hackel said. “But, so did furniture selection and its placement. Cubicle walls that were too high were a problem. The control system performed better when walls were at least 5 feet lower than window head height. We recommend recommissioning the daylight harvesting system if a space is repainted or furniture is rearranged.”
Both Hackel and Deringer advise that DLCx start early in the building design process, engaging discussions and communication among owners, designers, contractors and program managers from the utility that offers energy-efficiency incentive programs. It’s also an opportunity to catch mistakes before installation.
They recommend that key DLCx goals, objectives and specifics be included in the owner’s project requirements (OPR) and the basis of design (BOD) documents, so subsequent design reviews will contain metrics of the DL system. Deringer suggests a DLCx provider should expand the OPR to include illumination criteria, glare criteria, preferred control devices and electric-lighting-system performance characteristics. The BOD should include an energy-strategy list, a narrative of what is to be accomplished through DL, its parameters and zone diagrams.
“DLCx is an integrated commissioning process as it cuts across systems from lighting to other building operation and building design,” Deringer said.
The codes and standards driver
Rudimentary requirements for daylighting are already required by codes and standards such as ASHRAE 90.1 2010, Standard 189.1 for high performance green buildings, the International Code Council’s (ICC) optional green construction code (IgCC), California’s Title 24 and USGBC’s LEED certification programs. ASHRAE 90.1 2010 is currently being adopted now within certain states and municipalities. A more aggressive 2013 standard is on the way.
“ASHRAE standards are mandatory not prescriptive,” Deringer said. “I firmly see these ever stronger sets of requirements making daylighting a common building practice over the next five years.”
In California, lighting management systems are being recommended. Through Title 24, the testing of such systems and their daylighting components will only be allowed by those who have trained and certified under the California Advanced Lighting Controls Training Program. Further, certificates of occupancy will only be granted by buildings that have had their systems tested by certified individuals. While it is speculative that California’s actions are a portent of things to come across the country, it is an indication of the growing importance being given to DLCx.
The Building Commission Association, based in Beaverton, Ore., states that the number of organizations that advocate for DLCx continues to grow, including the American Institute of Architects, the Illuminating Engineering Society of North America, National Institute of Building Sciences, Lawrence Berkeley National Laboratory and others.
An opportunity for ECs
In its report, ECW authors saw a daylighting servicing opportunity.
“Recommissioning saved an additional 690 kWh per kilowatt of lighting energy in the median case and up to 2,420 kWh per kilowatt in the worst case,” the ECW write.
“Write it into your scope and get paid for it,” Hackel said. “Some owners might assume commissioning comes with the systems. Let them know most contractors aren’t doing it, but you do. Show them your plans, your calibration services. Explain the ASHRAE commissioning standard or LEED point opportunities. Add credibility through earning a certification through the Building Commissioning Association.”
Electrical contractors could bring this service in-house. Third-party agents have begun doing this work. According to Hackel, you will have to prove yourself. He suggested keeping up on the latest DL software and hardware. Training on it is essential whether offered by the manufacturers or other services.
“DLCx requires a commissioner who understands the design of daylighting and associated control systems,” Deringer said. “A DLCx commissioner knows how daylight levels interact with the space. Be that contractor who understands. The writing is on the wall when it comes to the accelerating growth of daylight harvesting. This could be the call for a good training program for electrical contractors.”