Facilities management officials in Pierce County (Washington) wanted to find a way to reduce natural gas heating costs at the existing Tacoma Jail and at a new addition, while also making sure the indoor air was as healthy as it could be. The adoption of ultraviolet-C ("UVC") lamps in the air handling systems has successfully met these dual challenges. The UVC energy emitted by the lamps constantly disinfects the air, making it possible to recirculate a portion of the indoor air while simultaneously killing viruses, bacteria and mold for enhanced air quality. The use of UVC technology is bringing the county an estimated $55,000 annual net savings.
"With the jail occupied to full capacity on a 24/7 basis, we previously had to bring in 100 percent outside air which was very costly to heat," explains Jim Loewen, project manager for the Department of Facilities Management at Pierce County. "Back in 2001, we did extensive research on UVC disinfection, and we predicted that we could safely recirculate up to 30 percent of the jails' ventilation air by installing UVC lamps in the air handling systems." By recirculating 30 percent of ventilation air, the county stood to save 34,102 therms of natural gas a year at the older jail, and another 39,491 therms at the neighboring addition under construction.
Local Energy Program Helps Cover Costs
Upon consulting with their utility, Puget Sound Energy, Loewen learned that PSE's energy efficiency program would cover half the cost of the initial UVC installation. In late 2002, more than 100 UVC lamps manufactured by Steril-Aire, Inc. (Burbank, California) were installed in the two facilities. The systems, which are tied into Honeywell controls, include carbon dioxide sensors that trigger increased or decreased air recirculation as needed, to a maximum of 30 percent recirculated air.
The UVC lamps are installed opposite the cooling coils in the air handling units, which consist of dedicated systems for each inmate cell area - mostly single fan systems built up with heating and cooling. On one air handler, where there is no cooling coil on the fan, the lamps are installed in the variable air volume (VAV) boxes instead. Installed in these locations, the high output UVC energy continuously kills bacteria, viruses and other harmful microbes and prevents them from spreading through the occupied space. This is an important benefit in correctional facilities, where the spread of infection is always of concern.
UVC also kills any mold and organic debris that may build up on the surfaces of the cooling coils. The mold control afforded by UVC has a dual advantage: (1) It helps maintain coils in "as new" condition, allowing them to perform more efficiently; and (2) It prevents mold-related allergens from recirculating through the building.
UVC output or intensity diminishes over time, so the light tubes are replaced annually according to manufacturer's recommendations, ensuring that sufficient output will be maintained to deliver the desired germicidal effect. The maintenance crew at the jail also performs quarterly visual inspections, at the time of air filter changeout, to make sure all lamps are functioning with no sign of damage.
"A review of our utility bills confirms that we have saved more than $70,000 a year in natural gas by reducing our outdoor air requirement through the use of UVC technology," reports Loewen. "Even after we subtract the parts and labor costs for servicing and changing the UVC lamps, annual savings still exceed $55,000."
Loewen adds that the lamps have created a healthier and more comfortable environment. "People used to call all the time, saying it was either too hot and stuffy, or too cold in the jail," he recalls. "We are not getting those phone calls anymore."
Additional benefits cited
Bob Hamilton, maintenance supervisor for the corrections facilities at Pierce County, admits to being the biggest skeptic when UVC was first discussed. "I was concerned that the big reduction in outdoor air would result in odor problems," he notes, "and we were considering the use of carbon filtration to offset any potential problems. We have found, however, that the UVC lamps do a good job of controlling odors, so we haven't needed the additional filtration."
Hamilton also reports: "The condensate pans are cleaner, and the algae growth we sometimes used to see on the coils is no longer evident. Coils have a cleaner, shinier appearance." He notes that, prior to installing UVC, they would brush the coils every three months and perform an annual pressure washing. Now that the coils stay cleaner, Hamilton has cut back on the frequency of these coil cleaning procedures, although the savings have not yet been quantified.
To use UVC successfully, Pierce County officials note that certain precautions should be observed. "Always follow the manufacturer's guidelines for proper lamp sizing, location and spacing within the system," says Loewen. "If the lamps are not applied correctly, they may not perform as expected."
Prolonged direct exposure to UVC (like other parts of the UV spectrum) can be harmful, so protective eyewear is necessary during inspection. Safety signage should also be posted on the air handlers so that service technicians know to turn the UVC lamps off when they are working inside the units. (An additional solution is to use lockout switches that automatically turn the lights off when a unit door is opened.) As another precaution, Pierce County wrapped exposed wiring and pneumatic lines in tin foil to protect them from potential UV degradation over time.
"Overall, we believe UVC technology is meeting our expectations for energy savings and enhanced IAQ," states Loewen. "Another stakeholder in the process, the Corrections Officers' Union, has been monitoring the program, and I believe they are pleased with the results as well. Energy savings and good IAQ are often regarded as conflicting goals, but with the use of UVC we have found it possible to achieve both objectives at the same time."