The Ice Man Cometh: Pros And Cons of Chilled Beam HVAC Systems
Having a comfortable space to live and work in is now considered a basic necessity, but at one time was an absolute luxury. In fact, the first public building to have indoor air conditioning was not until the St. Louis World’s Fair in 1904. The system used 35,000 cubic feet of air per minute to cool the 1,000-seat auditorium and other rooms within the Missouri State Building. It marked the first time the American public was exposed to the concept of comfort cooling. Since then, we have devised countless ways to cool a room, each more efficient and effective than the last. One method of cooling that has become popular in recent years is chilled beam HVAC systems.
A chilled beam consists of water piping that runs through a heat exchanger, or a “beam,” in the ceiling. Each chilled beam is a dedicated heating and cooling coil that is installed directly in each space. As people, equipment and other objects generate warm air in a room, the hot air rises to the ceiling and is circulated through the coils of the beam, which cools the air. The cool air then becomes denser than the warm air surrounding it and is released back into the room, where more warm air is cooled and the cycle continues. Ventilation air delivered to the beam also assists with drawing room air through the coil for increased heat transfer.
One of the most significant advantages of a chilled beam system is its efficiency and cost-effectiveness. They can effectively cool a room using lower primary airflow and move energy through the building with water instead of air, saving fan energy. Chilled beams can be 10-18% more energy-efficient than traditional HVAC systems. Their lower running cost saves clients money in the long run.
Chilled beams are also relatively simple systems to design and control. For example, they do not require condensate filters or pans, which reduces the long-term maintenance of the system when compared to those that do use these parts.
Cost-savings also come from the fact that there is no wasteful reheat. Each space has its own dedicated heating and cooling system with a thermostat that directs the system to open or close the hot and cold water valves on the beams as the room temperature rises and falls. There is almost no chance of over-heating or under-cooling a space because it’s all individually—but automatically—controlled.
Other benefits include:
- Less ductwork requirements
- Low maintenance
- No refrigerants
As with any method of air conditioning you choose, there are a few disadvantages to keep in mind. Firstly, unlike other A/C unit options that can cool multiple rooms with one piece of equipment connected to lots of ductwork, a chilled beam system requires that a heating and cooling coil must be installed in every room in the building. This increases the initial work and, therefore, installation price of the system. An accurate life cycle cost analysis and energy model can help the owner determine what the payback period will be on for this initial investment.
HVAC designers also need to consider condensate management with chilled beam systems. The chilled water in the chilled beam must be colder than the space air to cool the space, but warmer than the space dewpoint to avoid condensation. Otherwise, drip happens. In a well-designed chilled beam job, there are many safeguards in place to avoid condensation, but this is probably the number-one concern we hear from clients when we suggest chilled beam systems for institutional use. Chilled beam chilled water temperature must be selected and controlled correctly, and building humidity must be carefully controlled.
When selecting an HVAC system, it is important to weigh every factor and select one that is fit for you and your needs. When in doubt, call SHP. Our mechanical engineering team, myself included, are always happy to talk shop, weigh pros and cons and find the best system that will work for you!
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