I’m wondering if anybody has built a sauna with WikiHouse?
I think the only thing that would be any different to any other WikiHouse would be careful selection of membranes.
A high performance vapour control layer to the interior, perhaps with a reflective aluminium layer to reflect infrared. Or something like Intello DA. To keep humidity in and not diffusing into the structure.
And you’d be wanting to use a nice open rainscreen detail externally, to allow maximum drying of the structure to the outside, therefore a monolithic, black, water tight, UV resistant breather membrane such as Solitex Fronta Quattro externally.