Envelope Cx - whole-building air leakage testing

I think it is always good practice to have all of the Cx work performed by an independent contractor. Technically the testing contractor should be contracted directly to the owner too but there is a LEED Interpretation that allows the contract to be held by the contractor in a design-build scenario if certain conditions are met. Not sure if it applies to your situation - http://www.usgbc.org/content/li-10244

Sorry, I thought I had answered this...but probably just in my head. Often there are tests that require significant equipment, time, or coordination that go beyond a Cx firms abilities. One part of a commissioning plan is determining these kinds of tests and then including them in the construction documents and contract with the builders. If the CxA determines the tests that are required, provides a detailed specification on the test, what equipment and calibration is needed, qualifications that may be required of the testing agent or agency, AND then observes the test and reviews the request, then having the testing agency under the GC is fine.

One example would be ductwork pressure and leakage testing. This can be important, but since the ductwork system is still "owned" by the contractors at the time testing would be done, it would raise some difficult liability issues if there is not good contractual protection...ductwork has blown up more than once during these kinds of tests. So, having the test done under the MC contract is a good way to protect the owner from liability and having the CxA observe the test and review the report gives the confidence in the results.

Is LEED Interpretation 10244 (http://www.usgbc.org/content/li-10244) applicable to v4? I see that it says v4 in the Rating Systems Version section at the top, but the Ruling specifically refers to 2009 and v4 is not listed in the Applicable Credits section at the bottom.
If LEED Interpretation 10244 is not applicable to v4, does anyone know if it was replaced by something else, is somehow included in the Reference Guide that I am not seeing, or is not applicable to v4 for a reason?
Thank you!

Yes it applies to v4. I investigated this issue extensively for a design build project we are working on.

My big concern was that it contradicts some of the credit language for the Cx prerequisite. It says "for the credit, the CxA may not be an employee of the design or construction firm nor a subcontractor to the construction firm". This contradicts the ruling in the interpretation. I pointed this out to USGBC and after several back and forth emails they basically told me that the interpretation ruling supersedes the prerequisite language. I was always under that impression that credit language can't be superseded by an interpretation but I guess I was wrong. They do what they want apparently.

Yes, the LI does apply to v4 based on my own conversations with USGBC. I am not going to do a bunch of research on this but there is a confirmation of this LI in the guide and it is listed as a "special circumstance". What if after the LI this was published as an addendum to the guide, which can modify the standard? I use the on-line guide subscription now, so do not really look at the addenda much anymore. Anyway, settled law...mostly.

We are targeting the full 6 points under Enhanced Commissioning, including the 2 points for Envelope Commissioning.

Envelope Commissioning (2 point) requires the commissioning process to include ASHRAE Guideline 0-2005 and the NIBS Guideline 3-2012 Building Enclosure Commissioning Process BECx. I am struggling to find solid guidance in this document as to what the building air leakage or permeability rate should be. The consultant has stated a max permeability rate of 5m3/m2/hr at 50Pa in metric units.

The only target I can find in the NIBS guideline is from the NIBS Guideline 3-2012 Building Enclosure Commissioning Process BECx; (see "Procedure No. 1" in the "4. Testing Procedures and Record" table on page 320 of the document in the link): https://www.wbdg.org/FFC/NIBS/nibs_gl3.pdf

Could anyone share their views on targets to achieve this credit?

As I understand it the credit requirements do not establish a building air leakage rate. The project team does that and then the envelop commissioning would confirm that level of performance in the building, among other things.