The Rating System does not explicitly prohibit bypass systems; should they be disallowed?This CIR is based on a project in Canada with a bypass filtration system with a MERV-18 air filter. According to the project team: "With respect to Rodeo LEED Plantinum Certifications, the HEPA bypass filter works as follows: In continuous fan operation mode the continuous air handler moves aprox. 450 cfm. The Bypass HEPA system operates at 300 cfm. In my 20 years of designing residential mechanical systems, I have never put a HEPA directly into the air stream because it creates too much of a pressure drop. The bypass HEPA has no pressure drop and cleans 100% of the air in the house in less than two passes."
EQ 7.1 requires "air filter housings must be airtight to prevent bypass or leakage." Having a bypass is not acceptable unless both the bypass and primary return include a MERV-8 air filter. If there are multiple returns with different MERV-rated filters, the worst-case MERV rating can be used for the purposes of satisfying EQ 7. If the project wants credit for a weighted average approach, a full explanation of the weighting method must be submitted with some third-party reference supporting the validity of the claim.
Updated 10/1/13 for rating system applicability.