Thanks for the explanation Stitchawl
The 'real' question should be; 'why do the Japanese favor 'sliding doors' rather than what we are more used to in the west?'
Isn't it because you can have the house more open than a door would to have a view and fresh air? <-- just a guess. What is the reason?
I would think the real question is why not insulation? It would save valuable resources.