CWEB.046/OCTOBER.28.1999

# Keeping Close Tabs

### PNNL Office Buildings Experience Concludes That
Energy Conservation Measures Don't Ensure Efficiency

By Jeff Lettau and Launa Morasch
Pacific Northwest National Laboratory

(Editor's note: The following article originally appeared in the July/August issue of Facility Management Journal, published by the International Facility Management Association. It is published here with permission.)

In the early 1990s, new construction at Pacific Northwest National Laboratory in Richland, WA, provided facility managers an opportunity to study energy use in two office buildings.

Building One was completed in 1993. When a second building was designed with the same floor plan, PNNL staff encouraged a design that would incorporate energy conservation measures, such as low-emissivity windows, T-8 lighting, carbon dioxide ventilation control, energy-efficient motors for the HVAC system, and light-emitting diode (LED) exit lights.

Building Two was completed in 1994, and the mirror-image buildings stand side by side--one with extra energy conservation measures, the other without. This presented an opportunity to examine energy use in a real-world setting and determine what could be achieved through state-of-the-art system controls, energy-efficient windows and lighting, and sound facility management.

PNNL installed monitoring equipment in both buildings to monitor energy use for HVAC, lighting and outlets. This monitoring and subsequent analysis were supported by the U.S. Department of Energy's Federal Energy Management Program (FEMP). Energy conservation measures incorporated into Building Two were expected to save about 21 percent in energy costs compared to Building One, and occupant satisfaction was expected to be higher.

Initial data indicated the energy conservation measures may have worked. For the first two years of operation, Building Two showed less energy consumption than Building One--but not 21 percent. Then, in 1997, Building Two showed a surprising increase in energy consumption. By the end of 1998, Building Two was using 40 percent more energy than Building One and occupant complaints from Building Two were the highest of any building occupied by PNNL.

What Happened?

The only known changes to either building during this time involved the operating strategy of the heating and cooling systems. Facility managers made changes in response to occupant requests for increased comfort, particularly during evening and weekend hours. However, there was no record of when or why these manual adjustments were made. These manual changes continued to put the system out of alignment.

Software control experts theorized the heating and cooling systems were not being used to capacity. Upon investigation, staff found the heating and cooling system software had been manually altered and the temperature set points locked into place. Consequently, the system could no longer provide the designed level of control. The ability of the system to adjust temperature set points automatically to respond to changing outdoor conditions and indoor requirements was eliminated, which increased energy use and operating costs. In short, the heating controls were fighting the air-conditioning controls: Building Two was running the heating system and air-conditioning at the same time.

Staff from PNNL's facilities and operations department and the building sciences group tried to solve the problem by standardizing the operating schedules and analyzing the continuously collected data. Although four years of data were available, continual changes to the building operating schemes made it difficult to compare energy use.

The facility manager placed the controls for both buildings at the same settings (those specified for normal use) so variances in energy use could be attributed to the differences in the energy conservation measures installed in Building Two, rather than differences in how the buildings were operated.

Resetting the buildings to the same schedule required reprogramming the individual zone settings, duct settings and reference settings. In addition, special attention was needed to ensure identical damper controls. A preliminary analysis on the system hardware further eliminated differences in the buildings.

Courtesy of Pacific Northwest National Laboratory

Identical Control Strategies

The control strategies for the two buildings became identical in January 1999. On Jan. 5, 1999 the operating schedules of the two facilities were standardized. Four days later, someone discovered the duct temperature set point for Building Two had been manually set at 57 degrees. This resulted in mechanical cooling, even on the coldest days. The Building One duct temperature set point was also set low (61 degrees). The duct temperature set point in both buildings was reset to 67 degrees and was restored to automatic control so the heating system was not fighting the air-conditioning system.

On Jan. 13, 1999, the static pressure sensors for several ducts were found to be not working properly. Some appeared to have been inoperable since construction. This caused air handlers to run at full output, even though a reduced output would have sufficed. When the controls were set as specified, not only did the daily energy use drop significantly for both buildings, but Building Two is now using less energy than Building One--as it was designed to do.

The temperature set points for this normalized program were agreed upon by the facility managers, building owners and occupant managers. They agreed to a system setting of 72 to 76 degrees during daytime hours (6 a.m. to 6 p.m.) and a nighttime setting of 65 to 80 degrees. The energy management control system for each facility is a "smart" system, designed to attain the desired set point temperature at the desired time, 72 degrees at 6 a.m. The greater the temperature difference between indoor and outdoor temperature, the earlier the space conditioning begins. Thus, the control system "learns" from its previous experiences and is able to account for different building requirements and compensate accordingly.

The facility managers agreed that all calls from occupants regarding comfort would be investigated. If an office was outside the target range, it would be assumed a malfunction had occurred and appropriate actions would be taken.

Dramatic Improvements

Resetting the control systems produced dramatic results. Improvements in comfort level of the buildings and energy performance were noted immediately. When January 1999 days were compared to December 1998 days with the same average outdoor temperature, Building One total energy use had dropped 25 percent (2,400 kilowatt-hours per day) and Building Two had dropped by 47 percent (5,900 KWh/day). During the investigation into the software control systems, hardware problems were also identified that are now being fixed. Curing these problems will add even more to the efficiency of the buildings.

Buildings One and Two are now in adjustment. Some zones require continued efforts to keep the control systems in adjustment, but complaints about comfort have decreased, as the heating and cooling systems are no longer fighting each other.

Many Lessons

Many lessons can be learned from this experience.

- First, one should never assume the system is working as designed. Software failures, hardware failures or human error can be the underlying causes of most complaints. One of the major lessons learned from this situation is how easy it is for human error to offset the benefits of sound energy conservation. An adjustment that seems minor may put the control system out of alignment. Never perform "knee-jerk" adjustments on the system. Facility managers must understand all the options and effects before adjusting or changing any of the system controls. Facility managers at the laboratory learned not to adjust the overall temperature set points unnecessarily, but to adjust the volume of air delivered into the office space instead. Often, this achieves the same result without the energy impact when the temperature set point is changed.
- Facility managers need to track all customer complaints, even those that might not seem legitimate. Each complaint and its resolution should be charted. Documenting this history will provide insight into which facilities may be having problems.
- Dig for solutions and use new technology. Office temperatures were measured within the programmed temperature set points with regular thermometers. However, after using infrared sensing thermometers to track the duct discharge temperatures, a true picture of what was happening began to emerge.
- Don't be afraid to question the experts. Some people assumed that because equipment was supposed to operate in a certain manner, it was doing so. Questioning how the equipment was operating helped the PNNL team uncover new information. The team questioned how the system determined the correct duct temperature set point, which led to the finding that the duct temperature set points had been manually locked in place. The system experts claimed operators would not have access to manipulate these set points--but obviously they did. Some questions are still being debated. For example, how does the system alter the duct temperature set points and based on what input? How is this governed by the software for seasonal effects? How does the system know when to change a duct temperature set point versus simply altering a zone set point for maximum efficiency?
- In the process of tracking down the variations in energy consumption, facility managers need to be proactive about finding solutions. In these two buildings, everyone knew there was a problem, but no one wanted to be the bad guy who forced the systems back into the correct operating configuration, for fear it would make the building occupants unhappy.

The facility manager's first concern--after the safety of the occupants--is the proper operation of the facility. Once everything is working correctly, comfort issues can be addressed. More often than not, comfort issues will correct themselves once the system is working properly.

Also, the facility manager may want to determine if there is an incentive operating agreement with the utility or building owner that encourages energy conservation. In this particular case, there was no incentive agreement and PNNL paid the high utility costs without question, so there was no incentive to investigate high energy costs. The facility managers felt an incentive operating agreement might have helped solve the problem at an earlier stage.

The PNNL team learned there are no one-time solutions to these situations. Making energy management systems work requires continual supervision. Good configuration management and control is necessary if a building is expected to perform at the best possible level.

Without an ongoing monitoring program, energy use will drift out of control. Facility managers must be vigilant about tracking energy usage, logging changes to the system and tracking occupant complaints. This gives them the data they need to find solutions to system problems.--Jeff Lettau and Launa Morasch

More Information:

- Jeff Lettau, building manager, facilities and operations, Pacific Northwest National Laboratory: phone, (509) 372-6490; e-mail, jeff.lettau@pnl.gov; or Launa Morasch, PNNL technical editor: phone, (509) 372-6490

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