By Doug VerBockel

Ever hear of a Chilled Beam cooling (or heating) system?  I had not, until I attended a presentation about the one of the first such system installed in Wisconsin.  HGA Architects and Engineering firm (Kevin Allebach and Michelle Scanley) gave a presentation on the newly renovated UW- Madison Education Building on Bascom Hall.

So what is a chilled beam system?   Chilled beam is a type of convection HVAC system designed to cool (or heat) large buildings.  In a cooling system, pipes of chilled water are passed through a beam (heat exchanger) suspended in or a short distance from the ceiling of a room. (Refer to diagram below)

As the beam chills the air around it, the air becomes denser and falls to the floor.  It is replaced by warmer air moving up from below, causing a constant flow of convection.  There are two types of chilled beams.  Some passive systems rely solely on convection and there are other systems that rely on convection and radiant exchange.  The radiant exchange uses ducts to push air over the coils to increase the cooling capacity.

The main reason the chilled beam system was used for the Education School building at UW-Madison was due to the low ceiling height restraints in many parts of the old/existing structure.   This type of system can be installed with less plenum space required above the finished ceiling.

What are some of the advantages of a chilled beam system?   Physics tells us that water can carry more energy than air.  A 1 inch metal pipe can carry as much energy as an 18”x18” metal duct of air.  This means that a chilled beam system requires less energy to provide the same heating or cooling as a traditional HVAC system.  In the particular case in Madison, there was already a chilled water supply from the University’s main chilled water supply trunk.  Buildings also save money by being able to run fewer air circulation fans at lower speeds.  In one case, the Genomic Science Building at the University of North Carolina lowered its HVAC costs by 20% with an active chilled beam system.   Chilled beams are also almost noiseless and require less maintenance.

So, what are the disadvantages to a chilled beam system?  First, additional ductwork may be required to meet minimum outdoor air requirements.  Chilled beam systems cannot be used alone in buildings where ceiling heights are greater than 9ft high.  Another big consideration is dehumidification of the air over the chilled beam.  If the water temperature is too low or humidity is too high, condensation on the beam can occur leading to a problem known as ‘internal rain’.  Therefore chilled beam systems are not recommended for high humidity areas such as gymnasiums, cafeterias, theaters tropical climates and many hospital type of environments.

Well, there you have it.  Although the technology is not new, there are new adaptations and improvements to the system as time passes.  This system is just another option for heating or cooling that can be researched the next time you are involved in a building construction or renovation project.