Packaged heat recovery ventilators (HRV\'s) are commonly used in small systems (3000 cfm or less) that provide 100% outside air. These packaged units are not equipped with fans that can accommodate the additional pressure drop associated with MERV 13 filters. For example, the pressure drop for a MERV 13 filter is two to three times greater than a MERV 8 filter of the same size. Another common problem in small systems is that the pressure drop across the MERV 13 filter is equal to the static pressure for the entire distribution system, effectively doubling the ESP. Larger systems that use air handlers can overcome these problems through the use of larger fans. However, in most cases the relative impact of a MERV 13 filter is not as significant due to the higher static pressures associated with air handler systems. The same cannot be said for small, packaged, fresh air ventilators. It is clear from the Reference Guide and Credit Interpretations that the requirements of credit 3.1 apply to air handlers. However, is the credit criteria also intended to apply to small, packaged ventilators (3000 cfm or less) providing 100% outside air?
Although the language of the Reference Guide and previous CIRs specifically refers to "air handling units," smaller, packaged systems are not excluded from compliance. In order to meet the requirements of this credit, filtration media installed during construction (if systems are operated) and immediately prior to occupancy must have a Minimum Efficiency Reporting Value (MERV) of 13, as determined by ASHRAE 52.2-1999. Please refer to another EQc3.2 CIR Ruling (4/5/2004) for further information regarding filtration media. -- *NOTE (Nov 1 2007): Per errata posted in Fall 2007, there is no LEED or ASHRAE 52.2-1999 requirement for MERV 13 filtration during construction. LEED-NCv2.1 EQc3.1 requires MERV 8 filters on return air grills during construction, and for all filtration media to be replaced with MERV 13 immediately prior to occupancy/at the end of construction. Applicable internationally.