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Think “Chilled Beams” Instead of VAV Systems for Commercial Projects

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When a commercial customer is considering a Variable-Air-Volume (VAV) system for a new construction or renovation project, here’s an alternative that’s worth a second thought: chilled beam technology. In spaces where humidity loads are moderate (less than 25% of total heat gain) – such as open office areas, computer/server rooms, condo/hotel rooms, medical waiting rooms, libraries, museums, bank lobbies and retail stores – chilled beam technology proves to be an energy-efficient alternative.

Chilled beam technology employs coils installed in the space that leverage the heat transfer capacity of water, which is 3,500 times that of air, to provide sensible cooling. Passive chilled beams utilize natural convection to deliver cooling, while active chilled beams utilize high velocity jets of air to induce room air across their coils. This design provides several significant benefits, which include:

  1. Energy savings
  • Eliminates the costs of traditional air handling unit fans that consume a lot of energy to circulate a large volume of air. With active chilled beams, fan motor horsepower is reduced by 50 to 70 percent because the volume of forced air volume is minimal. As a result, annual fan/pump energy savings range from 30 to 40 percent.
  • Reduces the cost of reheat incurred with conventional HVAC technology, which has a tendency to overcool when actual cooling requirements are below design loads, then must be reheated to maintain setpoint. An active chilled beam’s minimal airflow facilitates delivery of cooling and ventilation without overcooling. As a result, reheat energy costs are reduced by up to 88 percent.
  • Cuts chiller operating costs, because a chilled beam can use a higher return water temperature, which increases chiller efficiency by 2 to 4 percent per degree. Moreover, dedicated chillers can be used to create opportunities for using waterside economizers, depending on the region. A dedicated chiller can be 40 percent more efficient when supplying 55 to 60°F water. As a result, the operational cost of a dedicated chiller for a chilled beam application is typically 15 percent less than a central chiller for a conventional system.
  1. Maintenance savings
  • Eliminates filters, because air is moving at low velocity over a dry coil surface, which dramatically reduces the amount of dust and contaminants in the supplied air. Active chilled beam technology is specifically exempted from requiring filtration by the International Mechanical Code (IMC) for commercial buildings.
  • Eliminates terminal blower motors within active chilled beam terminal units, which receive primary ventilation from the central air handling system fan motor. As a result, there are no terminal fan motors to replace, saving the replacement cost of $450 to $500 each.
  • Uses fewer components reducing maintenance and repair costs, lowering the 20-year life cycle cost by 20 to 25 percent versus more complex VAV technology.
  1. Structural savings
  • Reduces slab-to-slab spacing, because the low profile of chilled beams allows height reductions of up to 12 inches per floor, yielding average structural savings of $3.75 per square foot.
  • Reduces the size of components and shrinks duct cross-sectional areas by 50 percent or more along with the elimination of fan-powered terminal units.
  • Shrinks air handling unit size with an AHU footprint that is 30 to 40 percent smaller, increasing usable floor space. 

Chilled beams bring new benefits to today’s buildings

At a time when building owners and managers are facing complex building performance and budgetary challenges, contractors can suggest active chilled beams as an alternative to costlier VAV solutions. Utilizing smaller ductwork and smaller air-handling units than a VAV system, chilled beams offer significant space and energy savings in applications where sensible cooling is the primary need.

Jeff Scanes

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