Some buildings are renovated. Then, there are those which are positively transformed. When the former Seattle Opera House opens is its latest incarnation as Marion Oliver McCaw Hall, it will have preserved what is wonderful about the 75-year-old cultural center, while incorporating spectacular upgrades including excellent sightlines, expanded stage space, and an innovative HVAC System that puts a premium on comfort, acoustics, and energy efficiency.

The project is being called a transformation because while 30 percent of it comprises renovated sections of the old opera house, 70 percent is new construction. Building on the existing solid structure supports and foundation, the building owners were able to cut costs to a reasonable $125 mil- lion vs. $200 million for anew structure and shorten the need for the resident ballet and opera companies to temporarily relocate during construction.

And because the opera house was renowned for its excellent acoustics, the designers were deter- mined to not only retain that reputation, but also improve upon it with an ultra-quiet HVAC system design that had been in use in only one other performing arts center in the U.S. A key element throughout the system is the use of 260,OOO-square-foot of a rotary duct liner chosen for its superior acoustical performance.

Work continues at a busy clip as seen from the exterior of the completely transformed Marion Oliver McCaw Ball. the centerpiece of Seattle's cultural life. The 75-year-old building is undergoing a $125 million renovation that will enable the resident opera and ballet companies to return to the facility for the first scheduled performance next month.

A crane lowers HVAC components into the mechanical room of the new Marion Oliver McCaw Hall.

Hub of Cultural Activities

Built as the Civic Auditorium in 1927 and upgraded cosmetically in the early '60s to be the Seattle Center Opera House, Marion Oliver McCaw Hall is poised for its third re-incarnation of its life- time. It is expected to host 400 events in its first full year, an increase from 271 annual performances previously. It is home to two world-class organizations: the Pacific Northwest Ballet and the Seattle Opera. Nearly 600,000 people annually have attended performances, lectures, and presentations, and civic and social events, such as the Northwest Folklife Festival at the facility.

At nearly 75 years old, it was time to make major improvements to the facility. There will be a new lecture hall added that accommodates 388 people. In the 2,900-seat auditorium, there will be tiered box seats, additional restrooms, larger elevators, taller fly space, more wing space, and added stage traps. Other improvements include the addition of a new entrance and a dramatic transparent lobby, anew Cafe with indoor and outdoor seating, ADA and life-safety standards, and seismic reinforcement for the entire building.

The mechanical engineering firm of CDi Engineers was engaged to design a new mechanical system, the centerpiece of which is an upgraded and more responsive HVAC system. Several elements of the project, undertaken by the mechanical contractor MacDonald-Miller Facility Solutions, set it apart from other performing arts center renovations.

One element was the determination to preserve "the best [acoustics] in the world for opera," according to Speight Jenkins, general director of the Seattle Opera. Achieving that involved a number of requirements, including the installation of a very low-velocity HVAC system lined with CertainTeed ToughGard R rotary duct liner with a moisture-repellent surface. Another was the strict implementation of astringent indoor air quality specification that kept all ductwork in pristine condition at the sheet metal fabrication shop, during transportation and storage at the site, and during the installation phase. Finally, a highly unusual and innovative underfloor displacement ventilation system, designed for superior comfort and energy savings contributed to the overall excellence of the system.

Mary Ochoa, welder with MacDonald-Miller, works on a section of lined ductwork destined for use in the acoustically sensitive Marion Oliver McCaw Hall, home of the Seattle Opera and Pacific Northwest Ballet.

HVAC Insulation and Acoustics

MacDonald-Miller's mechanical contract for its work at the hall is valued at $13 million, much of which is devoted to the new HVAC system, which supplies 250,000 cfm of air. Low-velocity air is supplied to the acoustically sensitive spaces through sheet metal rectangular duct that ranges in size from small 6-inch x 6-inch to huge sections measuring up to 12 feet wide. The duct is sized larger than normal in some cases in order to meet the restrictive allow- able noise level.

The duct liner chosen for the application, 1-inch, 1-1/2-pound density ToughGard R, absorbs unwanted crosstalk, equipment, and air rush noise.

"MacDonald-Miller was wise enough to see that they had an acoustically sensitive project and that they should use the product that does the best job," said Norm Brown, P.E., project manager for CDi Engineers. CDi, based in Lynnwood, Wash., specializes in a wide variety of applications, including office and technology, cultural, healthcare, aviation, and government projects. Some of its more visible projects include infrastructure upgrades and renovations at SeaTac International Airport, now buildings and renovations at the University of Washington, public facilities in downtown Seattle, and many projects at healthcare institutions throughout the Northwest.

The rotary-based fiberglass liner with Enhanced Surface, anew moisture-resistant surface improvement, contains an EPA-registered antimicrobial agent in order to reduce the potential of microbial growth that may affect the product. The antimicrobial properties are intended to protect only the liner. "Our specifications required an antimicrobial agent in our duct liner," Brown pointed out, adding that all rectangular supply and return duct is lined.

Fabrication of the ductwork took place over a six-month period at MacDonald-Miller's 30,000- square-foot shop, which resulted in fabricating one million pounds of sheet metal for the Marion Oliver McCaw Hall job. The company recently acquired a new automated coil line duct fabrication machine that enabled it to boost its production from 200 pounds an hour to between 800 and 1,000 pounds an hour.

"Acquiring our new coil line put us in a more competitive position and improved the speed of our service to the customer," said Ray Burdine, purchasing manager for MacDonald-Miller.

The company typically employs 60 to 80 workers in its sheet metal shop. It purchases its HVAC sup- plies from Paragon Pacific Insulation in Seattle, a major HVAC distributor. MacDonald- Miller handles a full range of ser.- vices, including HVAC, plumbing and piping, sheet metal fabrication, and environmental services, and has a staff of approximately 1,000.

As duct sections were fabricated on a just-in-time basis, they were- loaded on MacDonald-Miller's fleet of trucks and shipped to the work site. Each section was tracked in the computerized system; bar coded, and then scanned when it arrived, so that it would be delivered to the right location.

Stringent IAQ Standards

Because the building owner was very concerned about assuring high indoor air quality of the entire HVAC System, an IAQ specialist was hired and immediately implemented an IAQ specification that may be a sign of a new industry trend. Operating under very stringent rules, MacDonald-Miller employees took precautions to protect every piece of lined ductwork from moisture and other contaminants. The goal was to avoid collection of fine dust and minimize any risk of mold growth due to the combination of dust and moisture during the production, transportation, and installation phases.

"Yes, we had to keep all duct liner wrapped in our shop. Once it was applied to the sheet metal, we had to seal each end with plastic to prevent dust and moisture from entering. Sealed duct sections were shipped on our trucks and were checked by inspectors to make sure each arrived in good condition," Burdine explained. "Then we would remove the seal from one end before we bolted it to the connecting section, leaving the open end still sealed. The goal was to always keep one end covered."

This sort of precaution is relatively new to the industry, agreed CDi Engineers' Brown. "Dust and moisture are becoming bigger issues during construction. The owner knew about this danger and wanted to take the necessary steps to protect the duct systems, including paying a premium for this service," he said.

MacDonald- Miller's Burdine noted that his company has changed its procedures overall in recent years in light of IAQ concerns.

"We're much more careful that dust and moisture do not enter the duct during fabrication now. CertainTeed's added moisture-repellent duct liner surface is also an added plus to the process. In fact, we've made the cleanliness of our production process one of our selling points lately. People have become very conscious about this issue," he said.

Large-sized runs of lined duct supplying conditioned air to the facility crisscross in the upper mechanical room of the cultural cente1; which includes a 2,900-seat auditorium, new lecture hall, and new cafe.

European Ventilation Design

CDi's unusual underfloor displacement ventilation system sets it apart from the typical American HVAC system design. More common in Europe, it has only been seen in the U.S. in recent years. Project Manager Brown had heard about this design and wanted to investigate its operation in person at the Newark (NJ) Performing Arts center, the only U.S. performing arts facility where the concept was completed and operational. While there, he spoke with the facility engineer and attended a concert to experience the system firsthand. Later, he and his staff did further research at an airflow laboratory in Atlanta and mocked up a theater riser system with 25 seats to perform their own experiments.

In traditional performance halls, air is supplied overhead, and air returns are through grilles located either under the seats or positioned low on the side wall. With the McCaw Hall system, conditioned air is supplied from underneath the seats. There are 8-inch supply air dif- fusers spaced at approximately every other seat that allow a relatively small amount of air to pass at a very low velocity. This is to keep the moving air noise at a minimum and keep patrons comfortable. A cushion of this conditioned air remains at floor level. The body heat of the patron induces a continuous convective flow of air upward, drawing the pool of conditioned air past their body. With this type of system, only the zone within 5 feet of the floor needs to maintain comfortable temperatures. The warm air ascends to the ceiling and is then returned to the central system.

"There are several advantages to designing a system like this," explained CDi's Brown. "One, you're delivering the conditioned air right where the people are located, so you're giving them superior air quality in terms of ventilation. Two, since the air is delivered where the people are, it can be delivered at a slightly higher temperature than traditional overhead systems, which contributes to energy savings and efficiency. The point is that we're conditioning the air where it is needed. We're not conditioning the entire space."