I'm building a garden hut (shepherd's hut style) and I've been looking around at examples other folk have built.
Some folks do not bother with an internal vapour barrier and I can't help thinking that they probably won't have any problems because a hut is not occupied for long periods like a house (gets a chance to dry out) and is generally much more "open" than a house. Door, window left open to the fresh air. Does it make sense to create a big, air-tight, polythene bag and then open the door every few minutes or sit with an open window (which due to small scale could be 15% of the total wall area) enjoying the bird-song. Surely I can do away with the vapour barrier in a 7ft x 12ft hut?
I've looked at this build:
http://www.greenwoodleathercrafts.co.uk/styled-23/index.html
And the chap has no vapour barrier internally and no exterior load-bearing skin other than the cladding rain-skin. Also no air gap between his breather membrane and cladding. However I can't help thinking that he will have no condensation problems at all and his hut will give decades of service.
My opinions are only gut-feelings from my experiences as an amateur self-builder. Any one got a more educated but open-mined view of the need for air-gaps/vapour barriers etc, in a garden hut?

How much insulation are you planning to have? How much vapour are you planning to generate in the hut?

David

Thanks for the opinions. It's very helpful to get ideas and advice.
Worst case scenario; two people come into the hut from a pouring wet, cold, Scottish, November day, take of their soaking jackets, turn up the stove for heat and boil a pot of soup or kettle. They keep the door shut for warmth.
So, in theory a lot of moisture could be generated indoors. Also sleeping in a small space like this could generate a lot of moisture, I guess.
I'll definitely go for the vertical air gap behind the cladding, we can get days of drizzly rain here and low fridge-lke temperatures (3- 8degrees C) for weeks on end. ( a real pain when you have some exterior painting to do). The cladding will need all the help it can get to dry out.
I was planning to use 75mm sheep's wool for wall insulation (for green-ness but I am swithering, the 450mm wide, rigid cavity board was a breeze to use in the floor). I am tempted by materials that do two things; that's green too.
The planned wall structure at the moment is:
From exterior: 15mm douglas fir cladding ( vertical board & batton), 12mm horizontal air gap, 12mm vertical air gap, 9mm OSB smartply, 75mm studs with sheep's wool between, Vapour barrier ??, 6mm or 9mm finished ply interior wall.
Floor is 9mm WBP FSC ply, 50mm Kingspan, 9mm ply with 75x50mm joists between (lying "flat")