Rating System

LEED BD+C: New Construction, LEED O+M: Existing Buildings, LEED ID+C: Commercial Interiors, LEED BD+C: Core and Shell, LEED BD+C: Schools

Rating System Version

v3 - LEED 2008, v2 - Schools 2007, v2 - LEED 2.2, v2 - LEED 2.1, v2 - LEED 2.0

Inquiry

Credit 3.1 and Credit 3.2 both state the requirement to replace all filters after construction (Credit 3.1) and again after the two-week building purge period (Credit 3.2) with MERV 13 filtration. This infers the LEED requirement of the building owner to permanently use MERV 13 filters in all roof top units (RTU\'s) after the building purge period and during building occupancy, as the same filters serve both return air and outside air in the RTU\'s we have installed (typical for most RTU\'s). Is this the correct credit interpretation? If so, we question the value of this requirement for several reasons: First, most typical roof top units provide two-inch thick filter racks within their filter and mixed air section where the return air and the outdoor air are mixed, filtered and delivered to the nearby evaporative refrigeration coil. This 2-inch thick filter limitation dictates the need for very expensive mini-pleated MERV 13 filters to meet the typical 350 to 500 feet per minute (FPM) face velocity at the filter rack of typical roof top units. Lower cost MERV 13 filters typically have a maximum face velocity of 125 FPM, which cannot be used in this application. With the limited size of the filter rack areas (undersized square feet of face area for a lower cost, low face velocity filter), we must use the more expensive mini-pleated MERV 13 filters. Secondly, the higher initial and final pressure drop of the mini-pleated MERV 13 filters (0.55 inches water column - initial resistance to air flow at 375 FPM face velocity*) compared to industry standard MERV 7 panel filters (0.22 inches water column - initial resistance to air flow at 500 FPM face velocity *) has a negative impact on typical roof top units by increasing the amount of fan energy required to operate the RTU\'s at a specified air flow. This fan energy usage increase can be substantial, raising the owner\'s energy costs over the building\'s lifetime while creating a subsequent negative impact on the environment. Thirdly, the higher face velocity, min-pleated MERV 13 filters are approximately three (3) times more expensive than low face velocity MERV 13 panel filters and approximately nine (9) times more expensive than standard MERV 7 panel filters used typically in the HVAC industry. Lastly, to encumber the owner with very expensive mini-pleated MERV 13 filters for the lifetime of their building appears to be an unreasonable side effect of this requirement. On this project, the building owner is a non-profit, community food bank organization where every dollar counts. We question the overall value of using MERV 13 filters in the HVAC equipment when lower cost and lower efficiency filters, when changed on a regular basis, will provide good air quality for the building occupants. In the final analysis, the intent of providing cleaner air quality to the building occupants using MERV 13 filtration has a fairly substantial negative environmental impact from the increased fan energy that MERV 13 filtration will cause. Our request for interpretation is this: In light of the above stated facts, can the building owner use the industry standard 2-inch thick MERV 7 filters in their RTU\'s once we have met the Credit 3.1 and Credit 3.2 requirements for MERV 13 filters? The maintenance and energy cost savings over the lifetime of the building would be substantial. * Published data from filter manufacturers cut sheets.