Many companies make sauna “kits”, which are basically log wall saunas. Interlocking logs at the corners, with double T&G logs.

These logs however are only 1.5″ thick, so they don’t have much insulation compared to an actual log cabin. This construction has drawbacks ,but they are very quick to build and ship to remote locations as well.

I’m wondering if there is a good way to insulate these. As an alternative to a traditional stick-framed build. I think it could be cheaper with materials and labour.

I’m thinking foil faced PIR insulation board inside, followed by 3/4 strapping, then 3/4 T&G. The FF PIR will hopefully be a good vapour barrier, keeping moist air in the room, and the strapping provides an air gap so any moisture behind the T&G can dry. Anything that gets through the FF foam could dry to the outside with T&G log walls?

Or could you do the same with the outside of the log walls? with an open cell foam board + strapping+ exterior siding