Personally wouldn't try to model it at all.  Just like we don't model dimple board on a foundation wall.  NRCan did a good job of describing cavities in Bulletin #85.  The bulletin had a google drive zip file. I think its a little large to post here or at least the video is.

It is appreciated that it is a closed cavity, consistent with Bulletin 85 and the webinar. 

I have been modelling it as a 3/8" air cavity (which is the thickness of the DrainVent), but this number is slightly higher than reality.

This issue is a rabbit hole, just wondering how deep others get into the details as we find it is these little things which can accumulate when modelling a high performance home.