I'm back again with more questions.

Our house project is moving right along. The ICF foundation is poured, the truss floor is on and the first two walls have gone up. Whatever time I have when I'm not building the house, I spend reading up and watching videos on "Super insulating", "REMOTE walls" and best building practices for a well sealed home.

I ended up going with 2x6 walls, mostly because my wife wanted the deeper window sills. The wall stack up currently is planned like this;

From inside out
Drywall
2x6 studs with R23 Rockwool
Zip sheathing and tape
2.5" Poly Iso
Furring strips
Cement board siding

I have been "caulking" or gluing the Zip sheathing to all the studs with Great Stuff Wall & Floor Adhesive. https://www.amazon.com/Great-Stuff-343087-26-5-Ounce-Floor/dp/B0045LPK2S. I bought a case of it for gluing the ICF and I'm really impressed with it! Once the walls dry they are ROCK solid and should be sealed up pretty well.

The plan was for me to get foil backed Poly Iso and tape all the seems with 3M flashing tape to further seal up the envelope. Given that I'm mounting the windows "in" I think I need some kind of drainage plane behind the foam (mentioned above). I'm using Zip sheathing so Tyvek Drain wrap seems like a redundancy and an area where detailing openings could get tedious.

Which bring me to my questions,

Should I go with paper backed Poly Iso and not tape the seems to allow more drying through the foam?

Would strips of 1/4" fanfold insulation under the foam provide an adequate drainage plane as discussed here?
http://www.greenbuildingtalk.com/Forums/tabid/53/aff/16/aft/81510/afv/topic/Default.aspx

Am I way off again?

Even fiber-faced polyiso is (almost always) a Class-II vapor retarder, a function of both the foam and the facer. Foil faced goods are easier to air seal, and provide a ~R1 performance boost when the foil is facing a 3/4" gap.

At 2.5" the labeled-R might be R15-R17, but in cold climates it's average wintertime performance could be as low as R12, which would require a Class-II vapor retarder (or smart vapor retarder) if you are in US climate zone 7 or colder.

https://up.codes/viewer/general/int_residential_code_2015/chapter/7/wall-covering#R702.7.1

With the drain plane located at rainscreen gap the foil facer on foam is an adequate drain plane. If flashing the windows to the ZIP as the drain plane instead of the exterior side of the foam, a crinkle-type housewrap between the ZIP & foam would be enough to get it to drain.

I'm thinking very hard about just moving to outie windows per the Zip system website. I've only got 2 windows framed and it's an easy change. Zip recommends a 1/8" minimum drainage gap. I don't think the drain wrap would satisfy that. No doubt it would work but should I have any other issues I'm sure the warranty would go out the window (pardon the pun).
Are you saying I may need an interior vapor retarder? Something like the Membrian you mentioned before?

You would only be looking at stuff like MemBrain or "vapor barrier latex" on the interior side if you are located in US climate zone 7 or colder.

http://www.greenbuildingadvisor.com/sites/default/files/images/DOE%20climate%20zone%20map.preview.jpg

The house is located in South western PA, Zone 5. Do you think Outie windows are the way to go?

In zone 5A 2.5" of polyiso will have a winter-seasonal performance of more than R13, which is more than adequate for dew point control.

Outie windows flashed to the outside of the polyiso works.

Time for an update!

Construction has been moving along. Slower than I'd hoped but there is progress. I've done everything myself to this point only having help 4 days for concrete pours and truss setting.

Here is the house as it sits more or less today.

[URL=http://s450.photobucket.com/user/GKG-MO/media/20171007_183537_zpskijuipcd.jpg.html][/URL]

I ended up with outie framed windows and 2.5" of Poly Iso foam. I'm sure my detailing isn't up to the highest standards and I've made a few mistakes along the way (You can see that small window in the front was framed in the wrong place at first) but so far I've passed all inspections with flying colors. Not too bad for an office monkey.

Electrical and plumbing are just about complete. Exterior foam and interior insulation will be going in about 2 weeks from now. There is some kind of shortage of Rockwool insulation in my area (or at least that's what I'm told). I've had 2 orders canceled so I'm moving on to plan B which is Cellulose behind netting. I've lined up a rental blower that is supposed to be capable of doing >4lb density, we'll see how it goes.

Just an FYI, you can't use Photobucket for hot-linking photos anymore unless you're paying for it.

And glad your build is going well. Sucks about the Rockwool.

Have you tried calling outside your area and asked about delivery costs (or considered a roadtrip with a box truck).