Thank you beech1948 for your comprehensive reply.
Just to be sure can I just mention that I have a large shed 18' x 15' which has been in situ for 5 years or so and in good condition.
I now want to insulate it. It does not leak.
The key features are that the construction is of 10mm thick shiplap...
I drew up the diagram as I had read through all the previous posts.
As some of them are old I just wanted to check if this was the current way of insulating a large shed.
Thanks to giantbeat and billybuntus and MARK.B. for your helpful replies.
As a newcomer I appreciate the hand holding.
I have an 18' x 15' shed with a 1 meter high apex roof.
I have had it about 5 years and would now like to turn it into a studio of sorts.
I have read all the previous posts and have created a chart which encompasses the essence of what a number of you have suggested.
Does my interpretation seem...