Sustainable Design

Staff | September 28, 2010

With its 29,000 square feet of convention, theatre, banquet, trade show, and classroom space evoking the natural beauty of the Willamette Valley, the Salem Conference Center is more than an eye-catching renovation in downtown Salem, Ore. It's an example of how sustainable design not only represents a region's natural beauty, but it can also contribute to the area's economic impact.

It was natural for the city to consider the center's environmental impact as well.

"Designing a sustainable building was a given, not only because of the region's appreciation for the natural environment, but also because we recognize that sustainable buildings reduce life cycle costs if they're designed properly," said Dan Riordan, revitalization supervisor for the city of Salem.

Sustainable design features range from recycled flooring to an efficient cooling system.

When summer temperatures require air conditioning, two McQuay 150-ton frictionless chillers and 23 McQuay Vision indoor air handlers condition and circulate the air. The equipment was chosen because it met project requirements for efficient operation and low sound levels. An energy cost analysis estimated that the HVAC system would provide 20-percent better efficiency than comparable equipment.

"A properly designed chilled water system can provide very good energy efficiency," said Ray Quisenberry, senior mechanical designer with Interface Engineering, Salem, who specified the project. "This project was of a size that provided for a decent payback period for the extra up-front first cost of a chiller system. The low operating cost of these particular chillers made the payback even better."

Added Quisenberry, "Noise control was also very high on the list of the owner's concerns, and noise and vibration from a central chiller plant is easier to design for and control than a more dispersed system such as rooftop package equipment or split systems." Sound pressure ratings for the McQuay chiller are 77 dBA per ARI Standard 575, among the lowest in the industry.

Introduced in 2004, the McQuay frictionless chiller uses R-134a refrigerant, which has no phase-out schedule or ozone-depletion potential. LEED recognizes this environmental feature and awards one point for systems that do not use HCFC refrigerants.

The key to the chiller's efficiency and quiet operation is the compressor's digitally controlled magnetic bearing system, which replaces conventional lubricated bearings. The compressor rotor and impeller shaft "float" on a magnetic cushion, which virtually eliminates vibration. To further reduce operating sound levels, the compressor's magnetic bearings eliminate the metal-to-metal contact noise of conventional bearings.

"While energy efficiency was a primary factor in choosing a frictionless chiller, operating sound levels were equally as important," said Joel Rohrs, senior project manager, Rushforth Construction, Tacoma. "The mechanical room is located on the third floor of the facility, and we wanted to mitigate noise and vibration as much as possible so visitors can easily hear lectures and presentations without background noise interruptions."

The air handlers, too, are designed for quiet operation, and no additional sound attenuation was added to the equipment. To further reduce sound levels, double-walled duct and duct lining were installed where necessary.

In addition to its vibration-free operation, the chiller consumes less power — and costs less to operate — than conventional chillers. The Conference center is not always occupied, so a chiller that could efficiently run at part-load was critical. Because of its integral variable speed drives, the McQuay chiller can operate down to 10 percent of its load with extraordinary efficiency. Energy usage at part load can be as low as .305 kW per ton. By comparison, a constant speed chiller would be forced to cycle on and off below approximately 25 percent load, resulting in less temperature control and more wear and tear on the compressor motors.

To further increase efficiencies, an underfloor, closed-loop hydronic system provides radiant heating and cooling. Underfloor pipes circulate cool or warm water as needed. When air conditioning is required, the Vision air handlers, which are equipped with variable frequency drives, supply cool and fresh air to every space of the conference center. Also, a large energy recovery unit transfers energy from building relief air to pre-condition fresh air entering the conference center.

Even though the residents of Salem waited a long time for their conference center, today they are enjoying the best of what sustainable design offers — not only a beautiful building that exemplifies the Pacific Northwest, but also one that showcases the best of energy efficiency and positive economic impact.

Story courtesy of McQuay International.