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October 25, 2007 UW lab showcases innovative cooling technologyBy GEOFFREY P. MCMAHON and PETER STRUPP
Affiliated Engineers
One of the most functionally diverse mixed-use neighborhood redevelopments in a major American city, Seattle’s South Lake Union is perhaps most admirable for its goals of becoming a sustainable urban community. Once the second phase of its Vulcan Inc.-developed South Lake Union campus is completed, the University of Washington School of Medicine will see its new laboratory building (UW Medicine Phase 2) benefit from and embody the principals of innovation, energy efficiency and sustainability. Research laboratories such as this fall squarely into a category of buildings in which the support provided by the facility and its mechanical and electrical systems is critical to the successful work of the building’s users. Innovative science requires innovative facilities. Pairing this correlation with a strong focus on sustainability and energy efficiency in a building type known for high energy consumption led to the innovative use of chilled beam technology for UW Medicine Phase 2.
What are chilled beams? The term chilled beam, which may seem to connote a structural device, is actually an efficient and sustainable HVAC technology that has been used in Europe and Australia for some time, primarily in commercial and academic environments. Simply put, a chilled beam is a convective cooling technology that can be configured as either a passive or active device to remove heat from a space. Mounted in an enclosure at the ceiling, a passive beam is essentially a chilled water coil that is able to generate air movement and cooling through convective currents created by warmer air rising in a space and colder air falling. Active beams are similar but have supply air ducted directly to them to increase the airflow through the device, thereby increasing its cooling capacity. In essence, these devices dissipate heat by using water as the transfer medium rather than air as is used in conventional systems. With the ability to absorb hundreds of times more heat than equivalent volumes of air, water provides a more efficient means of transferring energy.
Chilled beams in the lab
The use of chilled beams in laboratories provides opportunities to address many of the construction and operation challenges associated with these facilities, most prominently the need for large air-handling systems and ductwork and the substantial energy costs associated with that type of space. Typical laboratories can have peak airflow rates in excess of 15 air changes per hour (ACH). Delivering this amount of air with a conventional air-handling system can drive the floor-to-floor height for these buildings to 15-16 feet, compared to 12-13 feet for a typical office building. The use of active chilled beams can reduce peak airflows to 6 ACH or below, thus significantly reducing the size of equipment and ductwork, allowing the building to realize capital cost savings associated with a lower floor-to-floor height and significantly smaller mechanical rooms. Significant energy savings can also accrue through the application of this technology. Due to the use of chemicals in the lab and the potential for cross contamination between spaces, laboratories do not re-circulate air, as is common in most other environments. The reduction in air change rates using chilled beams can significantly reduce the energy profile of a laboratory, relative to the climate of the lab’s locale.
While other benefits such as lower noise, ease of control and lessened maintenance all contribute to making this technology viable for use in the laboratory environment, it is not appropriate for every lab. Labs in which the size of the air-handling system is driven by the need to replace exhaust air from devices such as fume hoods are not appropriate. However, equipment-intensive labs in which the air-handling system size is based on the need to dissipate generated heat are prime candidates for chilled beam technology.
Testing the technology Prior to the announcement of the UW Medicine Phase 2 project, Affiliated Engineers had teamed with the National Institutes of Health through its sustainable design initiative to identify ways to decrease energy use in laboratories. With the use of chilled beams identified as a promising technology, Affiliated Engineers developed a relationship with a major European chilled-beam manufacturer to test several configurations in laboratories. Through a full-sized mock-up process and extensive computational fluid dynamics analyses, one variation of chilled beam design was determined to optimize performance while accommodating maintenance access and the modular layout inherent in today’s laboratory design.
Testing for UW Medicine As the building function became better defined early in the design process for the UW Medicine Phase 2 facility, it became clear that building heat gain, rather than fume ventilation, would primarily determine peak air flow rates, thus making the project a prime candidate for active chilled beam technology. The design team — which included the UW, Vulcan and architect Perkins+Will — adopted the use of the technology after an extensive series of discussions, presentations and analyses. As the design progressed, Affiliated Engineers and the team performed additional computational fluid dynamics analyses and full-scale mock-ups in the beam manufacturer’s thermal test facility to customize and fine-tune the proposed design. This led to further efficiencies in the technology and a reduction of capital costs for the project.
Benchmarking
Upon completion in mid-2008, the UW Medicine Phase 2 building will be among the largest laboratory applications of chilled beam technology in the world. While the potential for energy savings would be more pronounced in a climate less temperate than Seattle’s, the qualitative impact and overall sustainable design benefits to the facility are significant. The reduction in system support space requirements will increase the net square footage of usable space, resulting in a greater degree of daylighting and more spacious labs. Lab spaces will also benefit from lower ambient sound levels and greater uniformity of temperature and air movement. UW Medicine Phase 2 is adjacent to the first phase of the School of Medicine’s South Lake Union Campus, which adaptively reused the “Blue Flame” building. The lab spaces and functions in the two buildings are closely comparable, though where UW Medicine Phase 2 will employ chilled beam technology, the first phase uses a more conventional HVAC system. This offers ideal circumstances for ongoing benchmarking of chilled beam technology, which is of great interest to the A/E/C field as well as the beam’s manufacturers.
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