Date
Inquiry

Chilled Beams & Re-circulated Air The project is a 6-story new consolidated forensic laboratory facility of approximately 351,000 square feet with approximately 140,000 square feet of laboratory space and the remainder typical office space. The office space and much of the lab spaces in the building will be tempered by active chilled beams. The remainder of the lab spaces with heavy equipment loads or special requirements will be served with fan coil units that will all be equipped with MERV 13 filters. Active chilled beams are located in or directly above the conditioned spaces. They utilize ventilation air that flows through the beam. The ventilation air passes through small air nozzles which induces room air through the cooling coil in the beam and provides overhead ventilation and sensible only cooling. This technology reduces energy and the architectural impact of ductwork and mechanical systems. Finally this cooler air will fall to the floor. Once the air heats up, it will rise back to the beam to be cooled again through the natural process of convection. The ventilation air supplied to the space through the beams will be single-pass, 100% outside air and will pass through MERV 14 filters at the air handling units before passing through the chilled beams. However, the project team is concerned that the natural process of convection utilized by this system may conflict with earlier Credit Interpretation Rulings (02/12/08, 08/13/2007, 08/08/2007) that state re-circulated air inside a single space must pass through MERV 13 filters. The nature of the system prevents filtration within the beams. The project team would like clarification if air re-circulated by chilled beams is held to the same filtration standards as a forced air system if the ventilation air provided to the chilled beams is single-pass and has already passed through MERV 14 filters?

Ruling

The proposed HVAC system design mixes 100% outside air from an air handling unit equipped with a MERV 14 filter with re-circulated, un-filtered air from the conditioned space. This request has been addressed by previous CIRs dated 2/12/2008, 8/13/2007, and 8/8/2007. The LEED-NC v2.2 Reference Guide states that filtration using a MERV of 13 or better must be applied to process both return and outside air that is to be delivered as supply air. Therefore, the system as described does not meet the credit requirements. NOTE: UPDATED CREDIT LANGUAGE FOR 2009 STATES THAT "PARTICLE FILTERS OF AIR CLEANING DEVICES SHALL BE PROVIDED TO CLEAN THE OUTDOOR AIR AT ANY LOCATION PRIOR TO ITS INTRODUCTION TO OCCUPIED SPACES". REQUIREMENT FOR FILTRATION ON RETURN AIR IS NO LONGER APPLICABLE TO ANY VERSION OF ANY RATING SYSTEM. Applicable Internationally.

Internationally Applicable
On
Campus Applicable
Off