This is what i do now,2x6 wall with r19 with tyvek(or equal HD/Lowes housewrap @ 1/2 price),One tyvek layer on the outside and one on the inside including roof of rooms,stapled to 2x6,whatever sheeting you like on the outside and inside..The tyvek breathes and plastic doesnt which makes it condensate.I use orcafilm instead of reflectix now,much better reflectivity.Foam board is badass but i think its overkill with 2x6 walls w/insulation,where i live it gets really hot(103 today) for months and it never gets over 72 in my empty rooms,I also have r60 in the attic(2 layers of r30).If your building from scratch when you sheet the roof use the foil coated OSB(reflects heat away) and put in a whirlybird for every 4-500 sq ft and vents in the eaves.Remember you want your walls to be able to breathe,moisture trapped will stay there!

you forgot the layer of bitchathane, and then some spray foam over the foamboard. LOL.

would that much insulation be necessary in places where it doesnt get that hot like in the nw? Im setting up a room as well but its in a basement, but i was almost gona just frame it , throw sheet rock up, then put orca film up and seal the room for co2 thinking that the heat could dissipate more if it wasnt very well insulated ( its in the basement and doing open hood )is this a bad idea?

Damn, that escalated quickly.