Chill the ceilings and achieve cool energy savings

August 11, 2010

U.S. designers are constantly scouring Europe, Asia, and Australia in search of new energy saving technologies—from double-wall façades in the 1980s to under-floor air distribution in the 1990s to digital lighting control schemes more recently.  

The “chilled beam” system is one the latest innovations to make its way to the U.S. market. Popular in Europe and Australia for more than a decade, the system involves placing cooling coils at the ceiling level to cool the rising warm air. The cooled air then gently descends to occupant level, providing a pleasant cooling effect with minimal air movement.     “Designers in Europe start with chilled beams as the baseline system, much like we start with VAV systems as the baseline here in the U.S.,” says Mike Walters, LEED, sustainable systems and energy analyst with Affiliated Engineers Inc., Madison, Wis. Walters says the technology has a lot of promise for offices, labs, healthcare environments, and even data centers. Engineers like Walters are hot on the technology because of potential energy reductions of anywhere from 20-50%, depending on the type of system, climate, and building. Laboratories that are heavily equipped are the most ideal application, says Walters, because they often require many more air changes per hour than is required by code to offset the heat gain from the lab equipment. “By cooling and recirculating the air, we can reduce the amount of air changes in a lab from 12 to 18 per hour to six to eight per hour,” says Walters. “That results in up to 50% energy efficiency.” With less air changes needed, Building Teams can downsize ductwork, air-handling units, exhaust fans, chillers, and boilers to help offset the cost of the chilled beam units and infrastructure, which can cost anywhere from $24-36 per sf for a typical lab facility, according to Walters. In fact, Walters says the savings as a result of the smaller HVAC components often exceeds the first costs of the chilled beam system (see chart page 26).


  • Other benefits include:


  •  High indoor air quality—air is reused locally, so there’s no contaminant mixing

  •  Space savings—no high-volume ductwork

  • eased comfort—no drafts, even cooling, and more pleasant cooling temperatures

  • maintenance/high life expectancy—no moving parts

  • risk of mold growth—computerized building automation control system carefully controls humidity levels.


are two basic types of chilled beams: active and passive. Active systems tie into the room’s primary air supply ducts, mixing supply air with existing air that is cooled by the coils, which is then distributed through diffusers in the ceiling. Passive technology relies entirely on the natural convection process, whereby warm air rises to the coils, is cooled, and then lowers back down freely without the assistance of fans. In both cases, water cooled to 59-65 degrees F is pumped from a chilled water system to each of the coil units.
Greg Mella, LEED, principal with Detroit-based SmithGroup, expects to achieve 50% energy savings with the help of a passive chilled beam system at Clemson University’s new $8.5 million, 25,000-sf Sandhill Research and Education Center. The system will incorporate geothermal technology, whereby water from a nearby campus lake will cool the coils.  “The lake water is 66 degrees Fahrenheit pretty much year-round, so we won’t need to chill the water too often,” says Mella. “The system will provide the bulk of the cooling for the building.”   Mella says the most common misconception about chilled beam technology is that the indoor humidity will condensate on the beams, especially in warm, humid climates like South Carolina. “Humidity control is key,” he says. “To make it work, you have to control the humidity internally so it’s always under the dew point.”
Walters says building controls have advanced to the point where condensation is a non-issue. “People think of the radiant panel technology of 20 years ago,” says Walters. “I have toured dozens of installations and there’s no condensation with these systems.” One drawback to the technology is the size of the units, says Robert Bucci, PE, LEED, principal with Affiliated Engineers. Bucci says the system components are bulky (about the size of a standard fluorescent light fixture) and can impede aesthetics of the interior spaces. “Even when the systems are installed flush to the ceiling, you’ll still have perforated metal ceiling tiles that the architect may not desire,” says Bucci. He says certain manufacturers will work with the design team to create custom designs that better adapt to the architecture of the facility and that incorporate key infrastructure components, such as lights, sprinkler heads, speakers, sensors, air nozzles, smoke detectors, and voice/data cables. Finding reasonably priced contractors to install the systems is another major concern. Most mechanical contractors are not familiar with the technology, and, therefore, will charge a premium or won’t take on the project at all. Bucci says it will most likely require a specialty contractor to complete the work.
For Mella, these concerns are minor drawbacks compared to the potential energy savings chilled beams can offer. “It’s a great concept, and I think it has tremendous potential in the U.S.,” says Mella.



         
 

Comments on: "Chill the ceilings and achieve cool energy savings "