Your HVAC system is one of your biggest energy consumers. Everything from blower motors and compressors to heat exchangers and chillers require electricity to operate. Because chilled beams have fewer moving parts, they can lower your operating costs.
Two professional engineers will help you determine if chilled beams are right for your building: Ken Loudermilk, Senior Chief Engineer with Johnson Controls brand Titus, and Kathryn Duytschaever, Associate with engineering consultancy RTM & Associates.
How do chilled beams work?
Loudermilk: Chilled beams allow decoupled treatment of sensible cooling loads from the space dehumidification and ventilation requirements. Their integral heat transfer coils utilize chilled water delivered at or above the space dew point temperature to perform most of the space sensible cooling at delivered airflow rates that are 60-80% less than that required by conventional all-air systems.
Duytschaever: Chilled beams have a fan coil but no fan. Cold and hot water supply lines connect to a heating and cooling coil. As air naturally crosses the coil, it becomes tempered. Control valves before the beam are connected to a wall thermostat that determines if the cold or hot coil should open.
What is the difference between passive and active chilled beams?
Loudermilk: Passive beams are not directly connected to the ducted air supply. A complementary air system must handle dehumidification and ventilation. Active beams use the pressure of the duct system to enhance the volume of entrained room airflow across their coils to significantly increase their sensible cooling performance.
Duytschaever: Both options work through convection. Active chilled beams have ventilation air ducted directly into the coils, which is then forced down into the space below. A passive system is placed above the ceiling in the plenum. Ventilation goes through a diffuser within the space while circulated air is forced up into the plenum.
Loudermilk: In North America, most applications have been active beams due to their higher cooling capacity. Passive beams have been used primarily in cases where the space above the ceiling is limited or to complement the perimeter cooling of underfloor air distribution systems.
What are the advantages of chilled beams over a traditional HVAC system?
Duytschaever: A typical HVAC system is tempering the air at the air handler and then pushing it through ductwork. The downside is that it requires a significant amount of energy to force air. By comparison, chilled beams circulate water through pipes. The advantage is that water can hold higher levels of heat and cold, switch between temperatures more easily and be transported more efficiently than air.
What are common barriers to adopting this technology?
Loudermilk: Most U.S. installations are new construction, though chilled beams can be an ideal solution for retrofitting old induction units under windows or noisy HVAC units in schools or hotels.
Duytschaever: Even though you will save money in the long run, chilled beams are more expensive up front because you still have to install a boiler and chiller. Chilled beams can cost up to 30% more per square foot than a conventional HVAC system. Part of the difference comes from labor because the piping is heavier than ductwork and requires more people to install.
What kind of upkeep is required?
Loudermilk: The fact that they require very little maintenance is one of the major benefits. As the system relies on chilled water delivered above the space dew point temperature, the coils remain dry and only require inspection every four to five years. Such coils are also exempted by building codes from requiring pre-coil filters, which also significantly reduces maintenance. No motors or blowers are involved so replacement costs are virtually nonexistent.
Duytschaever: As with any HVAC system, each piece of equipment needs to be monitored. If anyone’s complaining about it being uncomfortable, that’s a red flag. There might be a control valve failure or debris near the coil that’s preventing air movement. But most of your maintenance will be in the actual boiler room.
Jennie Morton is a contributing editor for BUILDINGS.