Air Side ; Air-handling units can only be ; Building must have very good external
downsized based on reduced air envelope with no leaks and good building
(DOAS) requirements and not full humidity control
cooling requirements, resulting in: ; Beams have less capacity output than
;
25 percent to 50 percent less air standard air diffusers
than VAV system must deliver ; Beams take up more ceiling space for
at peak load potential conflict with other ceiling-mounted
;smaller air handlers and ductwork devices if not integrated – lights, speakers,
; lower fan energy sprinklers, etc.
;elimination of reheat piping ; Dimensions may impact ceiling grid layout
; potential reduction in overall and require special installation details
building costs since floor-to-floor ; Space humidity and condensation sensors
heights and shaft dimensions required for better humidity control
may be compressed due to
smaller duct sizes
Water Side ; Uses warmer chilled-water Installation costs are higher because
temperatures and can extend ; chilled-water piping routed to each
free-cooling operating range, beam and each room
enabling large chilled-water delta T’s ; actual cost of beam high compared to
for smaller pipes and pumps other terminal units (cost discrepancy may
; Water is more efficient way of reduce as technology is applied more)
conveying cooling than air
(volumetric heat capacity or
specific heat), reducing air-side costs
; Similar to benefits of water source
heat pumps, warmer chilled-water
temperatures may not require vapor
barrier, and some designers even use
thick-wall plastic piping to provide
insulating effect so pipe insulation
not required
Operation ; Quiet as long as unit is selected ; Not appropriate for highly latent load
properly and too much primary air spaces or ceilings higher than 14 ft
is not used ; Not as appropriate for rooms dependent
; Provide good thermal comfort and on high heat gain or air change (labs)
potentially more air circulation ; Respond more slowly to varying cooling loads
Other ; Have reduced maintenance ; Typically come with two position on-off
requirements compared to HVAC control valves that are used since modulating
terminal units that have moving valves may create a laminar condition
air-side parts and dampers
Table 1. Advantages and Disadvantages of Chilled Beams.
Advantages Disadvantages
or This Old House, you always need the
right tool for the right job. CBs, while having
no structural properties, are the one beam
and tool that can build a bridge to new
technologies and lower energy usage, costs
and ultimately, carbon dioxide emissions.
And who doesn’t want that? So (chilled)
‘beam’ me up, Scotty! I am ready for some
chilling action.
The author thanks Rob Bolin, senior
vice president, Syska Hennessy Group, for
editorial assistance regarding chilled-beam
usage in high-performance buildings.
Based in Madison, Wis.,
Steve Tredinnick, PE, is
vice president of energy
services for Syska Hennessy
Group, which has more than
16 locations across the U.S.
He has more than 26 years’
experience related to building heating, ventilation and air-conditioning
systems. The past 15 years of his work have
been focused on district energy systems.
Tredinnick is a graduate of Pennsylvania State
University with a degree in architectural engineering. He is a member of IDEA and
ASHRAE and is currently immediate past chair
of ASHRAE TC 6. 2 District Energy. Tredinnick
currently serves on IDEA’s board of directors.
He may be reached at stredinnick@syska.com.
