When the City of Sammamish (Wash.) asked the design team to provide a LEED Silver certified building for the new city hall at the 25-acre Sammamish Commons redevelopment project, Notkin Mechanical Engineers (Seattle, Wash.) believed indoor air quality (IAQ) was of paramount importance. A key aspect of improved IAQ is to reduce the risk of human exposure to microorganisms that can potentially occur in public buildings. At the same time, the project team wanted to find ways to reduce HVAC energy and operational costs. The use of "UVC Emitters™" manufactured by Steril-Aire, Inc. (Burbank, Calif.), installed in the air handling units downstream of the cooling coils, enabled them to achieve both objectives as well as an ambitious third goal: to become the first project to earn a LEED® "Innovation in Design" point for the use of UVC germicidal lights in air handlers.
Being the first is never easy - so when Notkin project engineer Darren Schwend, PE, saw an opportunity to earn a LEED point for UVC, he had to put together a detailed narrative on its proven IAQ, energy, and coil-cleaning benefits. Working with Steril-Aire distributor Air Commodities, Inc. (Seattle), Schwend submitted published studies, articles and other support documentation to the U.S. Green Building Council (USGBC) to make the case for UVC.
"In fall of 2007, we learned that the project received an Innovation in Design point for UVC as well as the overall LEED Silver certification that we sought," comments Schwend. John Rowland, PE, Notkin partner, adds: "The application of high output UVC lights in mechanical systems is a practical technique that offers benefits for many types of buildings, and we are very pleased that the USGBC now recognizes UVC under their LEED rating system."
HVAC systems described
The new 45,000 sq ft building contains the Sammamish City Hall, police station, council chambers and public lobby on the first floor. A smaller second floor contains commercial space that will be initially leased while allowing for future growth of the city hall and police station. Located on the Sammamish Plateau, the facility is adjacent to a large civic plaza and public park with lawns, picnic shelters, and interpretive areas for viewing into the wetland habitat.
Heating and cooling is provided by two packaged rooftop air handling units designed by Petra Engineering. Both are variable air volume (VAV) units equipped with DX and hot water coils and are capable of 100 percent economizer cooling. AHU 1 (24,000 cfm) serves the first-floor municipal facilities, and AHU 2 (9,500 cfm) serves the second-floor leased space.
The UVC devices selected for the application are Steril-Aire single-ended (SE Series) UVC Emitters, which are specifically designed for rooftop systems. The high output germicidal devices are easily installed by making a one-inch hole in the equipment wall and then simply mounting the fixture to the unit exterior. Only the Emitter lamp penetrates into the system, while the power supply remains external.
How UVC works
UVC energy is the most germicidal wavelength in the ultraviolet spectrum. Properly installed in an air handling system, UVC lamps emit enough of this energy to penetrate even the tiniest microbe to destroy its DNA and RNA, killing or deactivating it. In this manner, UVC effectively stops both surface organisms that grow inside HVAC systems and airborne microbes that circulate through these systems to the occupied space. This includes viruses, bacteria, and mold and mold spores, which account for much of the illness and discomfort in buildings today and many of the maintenance and operational problems.
UVC continuously cleans the coils, reducing or eliminating the need for coil cleaning as a scheduled maintenance task. And because coils stay clean and free of mold and organic debris, they operate at peak efficiency, resulting in proven energy savings.
Sevda Baran, project manager for Sammamish Commons, says, "The air quality in the building has been excellent since the UVC lights became operational about a year ago. We are very satisfied with the IAQ and operational benefits, and we are excited to be the first project to use this technology for LEED credit."
Baran says that they run the lights "24/7" and plan to replace the Emitter bulbs on an annual basis as recommended by the manufacturer. These practices will help ensure that the UVC system maintains the germicidal output needed to prevent mold from growing on the coils or infectious microbes from circulating through the air.
"Precedent-setting"
Robert Scheir, Ph.D., president of Steril-Aire, Inc., which pioneered the use of UVC in air handling systems, states: "We too are gratified that UVC technology has received this important recognition for its proven performance benefits. The inclusion of UVC in the LEED rating system is precedent-setting and will reward other building owners, designers, engineers and contractors who take advantage of this technology in the future."
According to the USGBC: "Innovation in Design points are awarded to LEED projects that develop new solutions, employ new technologies, educate, or realize exemplary performance in another area.
Project credits
The architect for Sammamish Commons is ARC Architects (Seattle). Notkin Mechanical Engineers (Seattle) is the mechanical engineer. Commercial Filter Sales & Service (Seattle) installed the Steril-Aire UVC lamps, and PSF Mechanical, Inc. (Seattle) is the service contractor responsible for annual UVC Emitter replacement, filter maintenance and related scheduled tasks.
