This guy has some good basic discussion on why the barrel shape is a poor design choice and not used in Finland . http://localmile.org/blog/2020/11/05/notes-on

This guy has some good basic discussion on why the barrel shape is a poor design choice and not used in Finland . http://localmile.org/blog/2020/11/05/notes-on-building-a-sauna/ http://localmile.org/blog/2020/11/05/notes-on-building-a-sau... Basically there is not enough room in the bottom for cold air and the cold air Gradient is higher than it should be. There are all sorts of other design considerations, that impact the convection and air flow that i dont think these ever even thought about