Fastners on above roof deck insulation….gets crowded? – GreenBuildingAdvisor

So I’m continuing to plan our roof detail and started thinking about something which seems strange to me, but possibly I’m over thinking it.  

We are planning on this detail from our trusses up

1/2″ ZIP

2″ PolyIso

1″ PolyIso

1″ EPS

1/2″ OSB

Synthetic underlayment

Shingles

So I’ve got two questions in my mind.  

1- With the number of nails in each ZIP panel and then the screws in the foam and then 6-1/2″ SIP screws in the OSB….seems like you might be hitting some fasteners on the way in.  Is there some sort of technique here that will alleviate this issue?  Or is this not really an issue?

2- My ZIP layer will obviously be fully taped and will act as the air control layer of our home.  When I go to add the final layer of OSB to sandwich the insulation, I’ll need to drive those screws all the way through that ZIP panel down into the trusses, right?  Doesn’t this break the air barrier?  Or is this not a concern since it is under a minimum of 3 layers of staggered joints?