SEATTLE - City officials call the renovation of the 75-year-old Seattle Opera House a transformation.

When it reopened in June as Marion Oliver McCaw Hall, the historic character of the 75-year-old building was preserved while upgrading sight lines, expanding stage space and, according to contractors involved, adding an HVAC system that puts a premium on comfort, acoustics and energy efficiency.

Officials call the project a transformation because 70 percent of the $125 million project was new construction. Building on the existing solid structure supports and foundation, the building owners were able to shorten the need for the city's ballet and opera companies to use temporary facilities.

And because the opera house was renowned for its acoustics, the designers were determined 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 260,000 square feet of a rotary duct liner chosen for its superior acoustical performance.

Built as the Civic Auditorium in 1927 and upgraded cosmetically in the early 1960s when it became the Seattle Center Opera House, Marion Oliver McCaw Hall is poised for its third reincarnation. It is expected to host 400 events in its first full year, almost twice as many as it held its last full year of use. It is home to the Pacific Northwest Ballet and the Seattle Opera. Nearly 600,000 people a year visit the facility for performances, lectures, presentations and civic and social events.

Time for changes

But at nearly 75 years old, the city decided it was time to make major improvements to the facility. Plans called for an 18-month restoration and renovation project.

Among the changes:

  • A new lecture hall that would accommodate 388 people.

  • Tiered box seats and larger elevators in the 2,900-seat auditorium.

  • A new entrance and lobby

  • More restrooms

  • A cafe with indoor and outdoor seating

  • Seismic reinforcement for the entire building

  • Complance with the Americans with Disabilities Act

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

    One element was the determination to preserve what Speight Jenkins, general director of the Seattle Opera, called "the best (acoustics) in the world for opera."

    Erik Gladsjo of Hudson Bay Insulation puts in a piece of the more than 30,000 square feet of CertainTeed Standard Duct Wrap being used in various sections of McCaw Hall's new HVAC system. The duct wrap is used to improve thermal efficiency and protect against condensation in the duct system.

    HVAC impacts acoustics

    Keeping the acoustics intact required the installation of a very low-velocity HVAC system, which was lined with CertainTeed ToughGard R rotary duct liner with a moisture-repellent surface. Another requirement was the implementation of a stringent indoor air quality specification that kept all ductwork in pristine condition at the sheet-metal fabrication shop, during transportation, storage and installation. Also, the HVAC system featured a under-floor displacement ventilation system, designed for superior comfort and energy savings.

    Much of MacDonald-Miller's $13 million contract was devoted to the new 250,000-cubic feet per minute HVAC system. Low-velocity air is supplied to the acoustically sensitive spaces through rectangular duct ranging in size from 6-by-6-inches to sections measuring up to 12 feet wide. The duct is sized larger than normal in some cases in order to meet the restrictive allowable-noise level.

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

    "MacDonald-Miller was wise enough to see that they had an acoustically sensitive project," said Norm Brown, a licensed professional engineer and project manager for Lynnwood, Wash.-based CDi Engineers. CDi specializes in office and technology, cultural, health care, aviation and government projects. Some of its more visible projects include infrastructure upgrades and renovations at SeaTac International Airport, new buildings and renovations at the University of Washington, public facilities in downtown Seattle, and many projects at health-care institutions throughout the Northwest.

    Duct liner treated

    The rotary-based fiberglass liner with Enhanced Surface, a new moisture-resistant surface improvement, contains an Environmental Protection Agency-registered anti-microbial agent in order to reduce the potential of bacteria growth that may affect the product. The anti-microbial properties are intended to protect only the liner.

    "Our specifications required an anti-microbial agent in our duct liner," Brown said.

    All rectangular supply and return duct was lined with the substance.

    Fabrication of the 1 million pounds of ductwork for the project took place over a six-month period at MacDonald-Miller's 30,000-square-foot shop. The company recently acquired an automated coil line that enabled it to boost its production from 200 pounds of duct an hour to between 800 and 1,000 pounds.

    "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 specializes in HVAC, plumbing and piping, sheet metal and environmental services. It has a staff of approximately 1,000, about 60 to 80 of whom are in the sheet metal shop. It purchases its HVAC supplies from Paragon Pacific Insulation in Seattle.

    As duct sections were fabricated on a just-in-time basis, they were loaded on MacDonald-Miller trucks and shipped to the work site. Each section was tracked through a computerized system. Each piece had a bar code and was scanned when it arrived so that it would be delivered to the right location.

    IAQ system specified

    Because the building owner was very concerned about ensuring indoor air quality, an IAQ specialist was hired who implemented a specification system. MacDonald-Miller employees took precautions to protect every piece of lined ductwork from moisture and other contaminants. The goal was to minimize any risk of mold growth due to the combination of dust and moisture during the production, transportation and installation phases.

    "Once (duct liner) 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, Brown added.

    "Dust and moisture are becoming bigger issues during construction," he said. "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."

    Burdine said MacDonald-Miller has changed its procedures in recent years due to IAQ concerns.

    "We're much more careful that dust and moisture do not enter the duct during fabrication now," he said. "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."

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

    Seldom-seen ventilation system

    had heard about this design and wanted to investigate its operation in person at the Newark (N.J.) Performing Arts Center, the only U.S. performing arts facility where the concept was in use. While there, he spoke with the facility engineer and attended a concert to experience the system firsthand. Later, Brown and his staff did further research on under-floor displacement at an airflow laboratory in Atlanta. They also mocked up a theater riser system with 25 seats to perform their own experiments.

    In traditional performance halls, conditioned air is supplied overhead, and air returns are through grilles located either under the seats or positioned low on the side walls. In the system used at McCaw Hall, conditioned air is supplied from underneath the seats. There are 8-inch supply air diffusers 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 patrons' body heat induces a continuous convective flow of air upward, drawing the pool of conditioned air past their bodies. 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," Brown explained. "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."

    (This article was supplied by CertainTeed Corp.)