Currently finishing up my backyard shed.  I have 1/2 blue foamboard to go on exterior walls and roof (roof will be metal) that I will also tape. Floor has a layer of 3/4 blue foam board and 1/2 blue foam board in opposite pattern with all seams taped with OSB flooring caulked and painted. Have faced fiberglass to go in walls and ceiling. Foamed all small gaps. Designed the window layout and overhang to give me some passive solar in winter.  Trying to build the shed to remain as cool as possible in summer and as warm as possible in winter for storage.  The one element unsure of that has a lot of conflicting opinion is the use of a vapor barrier or moisture barrier? Opinions?  Inside, outside or both sides?

Sounds like overkill but I built this shed on piers with the same sled arrangement that the local Mennonite people use so they can move it. I am basically looking at the building for life.  My goal was mainly with enough passive solar/insulation to keep stuff from freezing and free up some space in my attached garage.

I did a 14x14 shed....concrete slab, 2x4 walls, T1-11 exterior walls, 7/16" OSB interior walls, R13 Batts in walls, R38 in ceilings, shingle roof.   It's comfortable year around in there.  If it got really cold, a light bulb would probably prevent freezing.

I looked at that T1-11 but hadn't decided. I usually do hardi-panel but that shit is VERY HEAVY and I was worried it might overdo the machines the Mennonites move with.  

I actually was thinking if the passive is not enough installing real doors in opening i am building doors in and building 1 - 2 small solar collectors to heat.  I am doing small scale stuff in preparation for a larger house project one day.

Plastic vapor barrier over unfaced bats. Never over the paper. One or the other with plastic being superior.