ID#2045 made on
EQc5 - Indoor chemical and pollutant source control
LEED BD+C: New Construction, LEED BD+C: Core and Shell, LEED BD+C: Schools, LEED ID+C: Commercial Interiors, LEED O+M: Existing Buildings
Our question regards the filtration requirement for re-circulating air systems, such as VAV terminals and fan coil units, under EQc5. Per the CIRs for EQc5 ruling dated 8/8/2007 and 8/13/2007, "S...
Our question regards the filtration requirement for re-circulating air systems, such as VAV terminals and fan coil units, under EQc5. Per the CIRs for EQc5 ruling dated 8/8/2007 and 8/13/2007, "Since the fan coil units re-circulate room air, they must have MERV 13 filters", so do the VAV terminal units that re-circulate air. This conflicts with our previous understanding that the MERV13 requirement would only apply to the air handling units supplying 100% outside air - or a mix of outside and return air - to a single or several rooms. The use of MERV 13 filters is justified when HVAC systems re-circulate a part of return air - e.g. mixed return air streams from various rooms - back to different spaces. In this configuration, supply ducts of the HVAC system and return air may become contaminated by re-circulated indoor-generated pollutants. Thus, contamination generated at specific indoor locations may be spread throughout the building unless properly filtered. However, the use of MERV 13 filters cannot be justified where air is re-circulated within the room. In this configuration, there is no possibility of cross-contamination: the re-circulated air has been conditioned and returned to the same room. In general, re-circulating air units (fan coils.) are provided with MERV 6 to MERV 8 filters. Using MERV 13 would substantially increase the energy consumption to condition a space without significantly improving the indoor air quality within the space. Imposing such a requirement would also cause most commercial systems to be ineligible for achievement of this credit, and may cause the other beneficial aspects of this credit (walk-off mats and isolation of harmful contaminants) not to be incorporated. Please clarify whether MERV 13 filtration is necessary for air re-circulated within a space.
As noted in the LEED-NC v2.2 EQc5 CIR rulings dated 8/13/2007 and 8/8/2007, both outside air and re-circulated air must pass through MERV-13 filtration before being introduced into a space, even if the re-circulated air is only being returned to the space it was drawn from. If there is a source of contamination in a space, filtering the re-circulated air before re-introducing it into the space provides a more rapid method of removing the contaminants than relying on the introduction of filtered outside air alone. 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.
Related Addenda (Corrections & Interpretations)