Should you insulate? The short answer is yes. But it is often not as a critcal as people think.
You insulate a home because the heat is on six months out of the year. A sauna is on for one to 1-1/2 hours. So, the insulation has a more limited value.
When building sauna, the stud cavity should be filled with R-12 (or R-13) Fiberglass Batt insulation. The insulation will be covered with the foil barrier that comes with our sauna material kits.
As rule of thumb, we discourage foam insulation (i.e.SM or blown). Foam has a lower heat rating. While it is generally OK for typical home sauna; for heaviliy used saunas it may deteriorate
Note on Pre-Fab saunas: Our pre-fab saunas are constructed using solid 2x6 cedar. While the solid log does not have as much insulation value as a fiberglass filled cavity, it is sufficient for the application. Keeping in mind that saunas are only on for 1 to 1-1/2 hours, the log construction is effective to contain the heat.
