July 2010 Addendum applies MERV 13 filtration to OA stream only?

I got the following note from USGBC, confirming how you guys were reading the new language:"The addenda was intended to clarify the systems requiring filtration and the credit is now as issued in the July update."

I think you could either ask for a CIR on it, or submit as an alternative compliance path, and hope for the best. But I am not expecting to see the credit language changed at this point.

Your interpretation is correct. The credit language was amended such that MERV-13 filtration is required on the outdoor air only. Of course, the filters can be placed in the mixed air path (return air + outdoor air), but they can also be placed in only the outdoor air path prior to its introduction into the occupied space.

Responding to John's comment on Sept 1 - Our project was registered before the July 2010 Addenda was issued. So we are required to have MERV 13 on the return and outside air that is delivered as supply air. We have dedicated outdoor air units that supply outside air to the return side of Air Handlers throughout the building. Isn't it correct that if we have MERV 13 at all the AHUs, filtering the return+outside mixed air, and only MERV 8 on the outside air equipment, that we meet this credit? The building owner requires MERV 13 at all the air handlers, so we are trying to figure out if LEED requires MERV 13 on the dedicated outside air equipment as well since the same air is going through the MERV 13 filters in the AHUs. Thanks!

Barbara, I can't speak to the technical issues in your question, but you can elect to rely on the July 2010 and later addenda.I just checked this with USGBC—projects are bound by the requirements of any addenda issued at date of project registration. But if an addenda is issued later than that, and it is favorable to the project, they can choose to use it.

Kim, I heard from USGBC that this addenda is intended to be available retroactively to all rating systems.