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Costs and Cost Models

Chilled-beam systems can be installed for the same cost as or less cost than the less-efficient VAV reheat systems typically found in buildings. With three or four products now manufactured in North America, the cost of chilled-beam units has come down significantly. Although chilled beams cost more than traditional diffusers, the cost is more than offset by significant reductions in ducting, shafts, and air-handler capacity. With first cost between chilled-beam and standard VAV-reheat systems being equal, operating costs make a compelling case for chilled beams, representing immediate energy savings of 50 to 60 percent.

Two recent office projects Rumsey Engineers designed verify the cost parity with VAV systems. In a new 80,000-sq-ft building in Palo Alto, Calif., chilled-beam costs were in line with VAV costs despite the chilled-beam design including thermostats in each room. In the design/build renovation of a 600,000-sq-ft building in Denver, the chilled-beam system was equal to a VAV system, but resulted in the elimination of two air handlers on each floor. The net present value of 20 years of leasing the space is $9.2 million.

In laboratories, the cost results are equally compelling. In a comparison of the first costs of a chilled-beam system and a standard VAV system for a 14,100-sq-ft laboratory, active chilled beams were shown to cost 84 percent of a standard VAV system, while active chilled beams with built-in lights were shown to cost 96 percent.

Contractors, Constructability, and Coordination

Few mechanical contractors are familiar with chilled-beam technology. Thus, it is important to keep an eye on installation costs and methods. In one case, estimated installation costs were suspiciously high; further investigation revealed contractors had estimated three to four times the actual time required for unit installation, largely because they were unfamiliar with the technology.

Chilled beams present relatively few constructability issues and generally do not require extensive structural support. Also, they can be effective in instances of tight spacing.

Most manufacturers recommend mounting a chilled beam in a T-bar ceiling and supporting the weight with wires or threaded rods, one at each corner of the beam. In seismic zones, additional guide wires often are required. To be lined up in a ceiling grid, chilled beams need to be adjusted in all three dimensions. Chilled beams need to move up and down so they can be leveled upon installation and made flush with the ceiling. Because chilled beams and their supply ductwork often are much shallower than conventional VAV boxes, they can save on the required floor-to-floor height of a building.

Commissioning, Operations, and Maintenance Issues

Commissioning chilled beams is similar to commissioning standard supply diffusers or duct heating and cooling coils. A chilled-beam water loop must be purged of air pockets during startup and throughout the life of the system. The lower flow through each beam's chilled-water coil can make purging air at startup difficult, so care must be taken to ensure each zone is purged. Experience with installed systems has shown that manual air vents are more reliable for purging air than automatic air vents. Special attention must be paid when manual vents are placed at high points in a chilled-water piping network.

Chilled-beam systems are less expensive to maintain than traditional VAV-reheat systems because of fewer moving parts. Higher chilled-water temperatures for non-condensing operation are more energy-efficient and allow more options in providing chilled water (e.g., expanded water-side free cooling and thermal-energy storage from nighttime free cooling). No fans or electrical connections are required, and a single room can be controlled with one valve and temperature sensor.

Chilled-beam coils require periodic cleaning, the frequency depending on the filter used at the AHU and the amount of dust in the space. Maintenance should include vacuuming the face of beam coils at least every three years. When designing a system, space beams far enough apart to allow easy access by maintenance personnel. Maintenance personnel need to be able to access beams from a ladder.

Sourcing

Historically, the leading manufacturers of chilled beams have been European or Australian. More manufacturers, however, are producing chilled beams in North America, which is resulting in cost reductions, better availability, and contractors becoming more comfortable with the technology.

Successful Installations

The Rumsey Engineers-designed Leadership in Energy and Environmental Design (LEED) Platinum Tahoe Center for Environmental Sciences was the first laboratory in the United States to use chilled beams. Other Rumsey Engineers projects incorporating chilled beams include the biomedical-sciences building at the University of California, Santa Cruz; the Cal Poly Center for Sciences; and the headquarters of The David and Lucile Packard Foundation in Los Altos, Calif.

Set to open in 2010, Constitution Center in Washington, D.C., features the largest chilled-beam system of its kind in the United States. The renovated 1.4-million-sq-ft, 10-story building, which is targeting LEED Gold certification, employs active chilled beams and DOAS heat-recovery units to accommodate limited ceiling space. According to SmithGroup, the project architects, modeling of the Constitution Center indicated the chilled beams provide a 54-percent reduction in required cooling energy.

Featuring an active-chilled-beam system, the $118 million, 166,000-sq-ft Jerry Yang and Akiko Yamazaki Environment and Energy (Y2E2) Building at Stanford University uses 50-percent less energy than a building adhering to ANSI/ASHRAE/IESNA Standard 90.1-2004, Energy Standard for Buildings Except Low-Rise Residential Buildings. Designed by Boora Architects and ARUP, the Y2E2 Building breaks new ground as a Beyond LEED facility, cutting energy consumption in half and reducing potable-water consumption by 90 percent.

Summary

Chilled beams are efficient because they decouple ventilation from conditioning, saving energy while improving ventilation and air quality.

While a chilled-beam system may cost more than regular VAV diffusers on the component level, the difference is made up in reduced ducting and piping costs.

U.S. designers and facility owners are becoming better informed about the benefits of chilled beams, and builders are becoming more familiar with the technology and how to integrate it into projects. Consequently, the cost of the technology is dropping, and barriers to the technology's adoption are falling.

Did you find this article useful? Send comments and suggestions to Executive Editor Scott Arnold at scott.arnold@penton.com.

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The founder and managing director of Rumsey Engineers (part of Integral Group), the first engineering firm in the United States with six Leadership in Energy and Environmental Design Platinum projects to its credit and the recipient of numerous local and national awards from the likes of The Association of Energy Engineers and The American Institute of Architects, Peter Rumsey, PE, CEM, FASHRAE, FRMI, has designed mechanical systems for data centers, cleanrooms, and laboratories that are among the most energy-efficient in the United States. He lectures at industry events, conferences, and colleges and universities, including the University of California at Berkeley and Stanford University.

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