Chilled beams are among the recent energy-saving innovations
making their way to the U.S. market. Chilled beam technology, which
involves locating a low-temperature radiator at ceiling level to
cool the rising warm air, has been utilized in Europe and Australia
for more than a decade. Once cooled, the air slowly descends into
the occupied zone, providing adequate cooling with minimal air
movement and fan power, while providing an unobstructed radiant
heat sink above the occupied zone.
Chilled beams have emerged in the United States as an attractive
alternative to variable air volume (VAV) systems and have been
proven to be effective in conditioning both new and existing
buildings. Their flexibility, ease of installation and maintenance,
and energy efficiency present a cost effective alternative to more
conventional cooling systems.
Chilled beams can be classified into three different categories:
Passive Chilled Beams, Active Chilled Beams, and Multi-Service
Chilled Beams. The distinguishing characteristic of each design is
the type of air flow utilized and the means by which fresh air is
provided to the space. Common to all types of chilled beams is the
radiator element, which uses circulation of chilled water as the
source of radiant cooling.
Chilled beam technology is most applicable to interior
environments where heat gain in the space - solar radiation,
people, or equipment heat - is the primary factor for determining
air flow quantities. This refers to spaces where the amount of air
required to cool the space surpasses the amount of air required by
code to maintain acceptable indoor air quality. Therefore,
hospitals and laboratories are facility types thinterat are
particularly well-suited to using chilled beams.
Passive Chilled Beams
Passive chilled beams are akin to finned-tube radiators
positioned within the ceiling cavity. Perforated metal tiles allow
warm air to flow from the occupied zone to up the beam in the
ceiling cavity. This passive technology is operated purely from
natural or free convection, whereby the warm air rises to the
radiator, is cooled, and then descends naturally without any
mechanical fans. Passive chilled beams are typically employed to
offset perimeter heat gain in a building. They are also often
displacement ventilation systems.
Figure 1 - Chilled beam (Photo
Active Chilled Beams
Active chilled beams incorporate tempered ventilation air,
supplied through ducting in the beam itself, and provide
ventilation air to a space through induction nozzles. These nozzles
create a pressure differential across a cooling coil, "inducing"
air flow from the room across the coil and supplying cool air back
to the room that is a mixture of the tempered ventilation air and
the recirculated room air. The cooled air enters the room via
outlet slots on the underside of the beam. Because they rely upon
powered air movement, rather than just buoyancy, active beams can
also be used for heating by supplying hot water to the heat
Multi-Service Chilled Beams
Mutli-Service Chilled Beams are similar in function to active
chilled beams, but they may also act as a conduit to supply other
building services such as lighting, speaker systems, IT systems,
fire protection (sprinklers and detectors), acoustic insulation,
Building Automation System sensors, and photocells.
A number of thermal comfort and energy benefits can be derived
from incorporating chilled beams into the design of a building.
Chilled beams can provide potential energy reductions from 20 to
50%, depending on the system design, building details, and climate
zone. One particular energy-saving advantage of chilled beams is
the ability to use higher chilled water supply temperatures (65°F
to 59°F). This allows the chiller system to operate more
efficiently and to potentially make greater use of waterside
In addition, chilled beams allow fans to operate at lower
speeds, meaning that both the fans and chiller are doing less work
to achieve the same amount of cooling as in a conventional
As mentioned above, designing ventilation rates for occupancy
rather than to offset heat gains can reduce the number of air
changes per hour in laboratories and other buildings with large
internal equipment loads, resulting in further energy savings. For
example, in a typical laboratory, ventilation rates can be reduced
from 12 to 18 air changes per hour to 6 to 8 air changes per
Smaller Equipment Required, Smaller First Cost
With fewer air changes needed, ductwork, air-handling units,
exhaust fans, chillers, and boilers can all be downsized. In new
construction, this avoided first cost can help to offset the cost
of the chilled beam units and infrastructure. Even in 2005, with
contractors relatively unfamiliar with the technology, the savings
from downsizing the HVAC components were found to offset the first
cost of an entire chilled beam system.
|Chilled Beams Case Study
Constructed in 2004, the
Tahoe Center for the Environmental Sciences utilizes chilled
beams to efficiently deliver comfortable working conditions to its
occupants. The 40,000 square foot building with 10,000 square feet
of laboratory space was awarded LEED® Platinum Certification in the
summer of 2007, having achieved energy savings of 60 percent over
ASHRAE 90.1- 2004.
click to enlarge
On warm days when outdoor air temperatures exceed 68F, chilled
water between 55°F and 60°F is used to supply 68F ventilation air
to the chilled beams in order to cool the laboratory spaces.
By contrast, on cold days where the temperature drops below
55°F, ventilation air is pre-heated to 55°F, and then heated
further in each laboratory space, as needed.
This strategy eliminates the need for reheat, and allows for
untempered outside air in the space when temperatures are between
55°F and 70°F.
Futhermore, such systems allow for reducing the size of the
ducting system and air handlers by one third.
Indoor Air Quality
Depending on the location, air may be re-used locally with
chilled beams, so no contaminant mixing occurs. This results in a
cleaner, healthier indoor environment, without energy penalties for
introducing large quantities of outside air. Although chilled beams
are well suited for managing the cooling loads in some
laboratories, they can be an unacceptable solution in others due to
heightened indoor air quality concerns. In areas with potentially
dangerous contaminants, many laboratories prohibit
Depending upon the type of installation, chilled beams contain
few or no moving parts. The fact that there are no internal fans or
filters to repair or clean accounts for a long life expectancy and
hassle free operation. In general, all maintenance associated with
a chilled beam system will be at the central plant. This compares
favorably to HVAC systems that have dampers and/or actuators at
each terminal box.
Figure 2 - Active Chilled Beam
Cross-sectional schematic of an active chilled beam. Both
air (introduced through nozzles) and warm recirculated air (from
zone) are cooled as they pass by the chilled beams cooling
As with any technology, chilled beams also have some some
limitations. Here are a few ways in which chilled beams may require
In humid climates, humidity controls may be a necessary addition
to chilled beam systems. If not properly controlled, humidity
levels may cause condensation on the surface of chilled beams. To
avoid this problem, the internal humidity must be controlled such
that the beam temperature is always above the dew point temperature
of the air. A rule of thumb states that relative humidity should be
kept below 50°F to 55°F dew point. This is equivalent to a maximum
relative humidity of 50% to 55% at 72°F. If it is not possible to
control the humidity in the space, chilled beams may not be the
preferred method for providing space cooling.
Many of the benefits derived from chilled beams come from their
ability to recirculate the air within a space. When necessary,
fresh ventilation air can be provided via conventional means or as
part of an "Active Chilled Beam" system.
Chilled beams can be integrated into a ceiling grid or left
exposed. Aesthetic considerations may also include minimizing the
visual impact of the beam. Manufacturers may work with design teams
to customize the appearance of the chilled beams through molds and
extrusions that better adapt to the facility's architecture. In
addition, the design and layout of chilled beams may incorporate
key infrastructure components, such as lights, sprinkler heads,
speakers, sensors, air nozzles, smoke detectors, and voice/data
The design team must consider the location and spacing of
chilled beams to ensure adequate coverage of the space. In order to
achieve proper interior thermal comfort, the building automation
system or building operator can chose to control chilled beams
individually, or controlling grouped regions of chilled beams.
Passive beams are virtually noise free, as no fans are
incorporated into the system. Active beams utilize relatively low
airflow rates-typically around 40 CFM. However, it is recommended
to incorporate a suitable acoustic in-fill membrane into the design
to enhance sound absorption, without inhibiting air flow to or from
One 2005 study showed that in one typical 14,100 square-foot
laboratory, installation of a chilled beam system was less than the
cost of a standard VAV system, coming in at just 84% of the cost of
the conventional system. Even a chilled beam installation with
integrated lighting cost just 96% of the VAV system installed first
Chilled beams may not be an effective solution for spaces with
exceptionally high cooling loads, which would require an
impractical number of chilled beams to be installed in the ceiling.
Spaces with such loads will likely be better served by a
conventional cooling system.
California utilities offer outstanding educational opportunities
that focus on the design, construction and operation of
energyefficient buildings. Listed here are a few of the many
upcoming classes and events; for complete schedules, visit each
Implementing Energy Efficiency Projects
Energy managers and maintenance professionals will learn how to
perform energy assessments, screening audits, feasibility studies,
and the selection of proper equipment for commercial and industrial
facilities. Come learn how to do a basic audit of your facility to
determine if new equipment is worth the investment.
read more >
Title 24, 2008 is now in effect
Most utilities will be holding training sessions to discuss the
latest revisions to the envelope, lighting, and mechanical
components of Title 24. The new standards took effect January 1,
2010. Edison CTAC: "Title 24 Energy Efficiency Standards - What to
Expect in 2008/2009?"
read more >
San Diego Energy Resource Center: "Preparing for California's
New Nonresidential Title 24 Standards."
read more >
New PG& E Training Schedule
The Pacific Energy Center and the Stockton Training Center will
issue new schedules at the end of January.
read more >
Introduction to Life-Cycle Costing
Life-Cycle Costing (LCC) is an economic analysis method that helps
building owners, designers, and operations managers assess the cost
benefits of energy efficient technologies, designs, and operations.
Using interactive discussion and examples, attendees will learn
about the role of key assumptions and how to interpret an LCC
read more >
Benchmarking with ENERGY STAR Portfolio
As of 2010 non-residential building owners and operators will be
required to disclose Energy Star Benchmarking ratings on their
lease to prospective lessee, buyers or lenders. More than 9 billion
square feet of US buildings have already used US EPA's ENERGY STAR®
portfolio manager tool. This fast-paced course will address the
pros and cons of various benchmarking techniques, tips for
optimizing your ENERGY STAR score, and best practices for improving
the score over time.
read more >
Don't miss future issues - to sign up for a free email subscription, please visit our
newsletter subscription page. Send letters to the editor, suggestions on topics for future
issues, or other comments to the e-News editor via our
Comments & Feedback form.
e-News is published by Energy Design
an online resource center for information on energy efficiency design practices in
Savings By Design (www.savingsbydesign.com)
offers design assistance and incentives to design teams and building owners in California
to encourage high-performance nonresidential building design and construction.
Energy Design Resources and Savings By Design are funded by California utility customers
and administered by Pacific Gas and Electric Company, Sacramento Municipal Utility
District, San Diego Gas and Electric, Southern California Edison and Southern California
Gas Company, under the auspices of the California Public Utilities Commission.