Chilled Beams, meet Passive House

Chilled beams are a proven technique for heating and cooling rooms using a very low air flow rate that saves fan energy. Recent chilled beam advances incorporate demand control ventilation techniques to maximize energy savings. Simultaneously, Passive House building techniques are applied to increasing numbers of building projects. Although Passive House and chilled beams share common energy saving ideas, they have not been applied together in most building projects.

The original intent of chilled beams, conceived of in Scandinavia in the 1980s, was to provide a ceiling-based cooling terminal device to accompany constant airflow ventilation. Today, chilled beams also provide heating, variable airflow rates and are available in ceiling, wall and floor-mounted varieties.

Demand control ventilation (DCV) has also been widely applied in North America. DCV meets the requirements of the latest ventilation codes, permitting the reduction of airflow as the demand for ventilation decreases. For instance, if design occupancy for a conference room is fifteen people, then the ventilation system must be capable of providing code-required airflow for fifteen people. Typical conference rooms are not always fully occupied, so it stands to reason that less-than-design airflow rates are appropriate much of the time. DCV, for example, allows the ventilation system to respond to an occupancy of five by reducing the airflow to a rate that meets code for five people. The reduction in airflow results in reduced ventilation system fan work, saving considerable energy.

Chilled beams save energy when in constant volume mode. Imagine the energy savings when DCV is added to the chilled beam control logic. The chart nearby shows a fifteen year life cycle cost (LCC) analysis for a recent application of chilled beams in hotel guest rooms. The DCV chilled beam system offered the lowest LCC of five system types considered.

Early attempts to combine chilled beams with DCV using Variable Air Volume dampers upstream of the chilled beam proved to have minimal success. As the VAV dampers reduced the airflow during periods of reduced occupancy, airflow at the chilled beam inlet decreased, starving chilled beams of the air pressure required for proper room air induction, unintentionally reducing comfort and temperature control. The airflow could only be reduced by about 30% before the nozzles became starved of pressure.

Technology introduced around 2012 allows chilled beams to overcome the starved-nozzle problem, allowing a turndown closer to 9:1 and many commercial office spaces, hotels, classrooms and single person offices are experiencing greater energy savings and comfort as a result.

NZEB uses chilled beams, why not Passive House?

A Net Zero Energy Building, Tour Elithis in France has been occupied since 2009 and is now a documented net positive building. The building is not Passive House certified, yet uses many of the construction techniques found in Passive House projects. Chilled beams are the primary ventilation terminal device.

The National Renewable Energy Lab, in Building Zero Net Energy (ZNE) Communities Passive House Design & Smart Home Technology, also implies benefits of using chilled beams in net zero buildings.

Several Passive House certified buildings are already using chilled beams, just not yet in North America:

• Tesco grocery store in Ireland
• Number Two Grand Canal Square offices also in Ireland

A PHI-certified building using chilled beams was proposed by Net Zero Analysis, but was apparently not built.

The chilled beam and Passive House concepts have three similarities:

1. Net Zero - Passive House projects are intended to be Net Zero ready, and chilled beams are already used in Net Zero Energy Buildings.
2. Minimum Ventilation - By definition, Passive Houses are intended to be temperature controlled using no more than minimum required ventilation air, matching the original chilled beam concept.
3. Demand Control Ventilation - Passive House ventilation systems typically use unoccupied, occupied and boost air flow settings to maximize energy savings, a DCV feature offered by the latest chilled beams.

Which project will be the first in North America to successfully employ chilled beams in a Passive House project?

#Passivehouse #passivhaus #chilledbeam #netzeroenergy #NZEB #DCV #demandcontrolventilation