Air Gap

  As our sauna is in an enclosed room and not freestanding it won't need exterior panelling.  It will, however, need an air gap between the outside of the sauna and the wall of the existing room.  This allows the sauna walls to breathe and prevents condensation from forming.

The air gap is created by using timber spacers.  The Nordic booklet also recommends the use of building paper.  I'm told that heavy duty Viskween (a damp proof membrane available from builders' merchants) will also perform satisfactorily.  As it is on the outside of the insulation, it should not be affected by the heat.  Having said that, the person who I visited has also used Viskween between the insulation and the interior panelling.  He tested it first by baking it in an oven and it apparently suffered no ill effects.