Sauna in the basement, what should be considered?

Hello everyone,

after completing my bathroom project, the next one is due now... a sauna needs to be installed in the basement. :-)

The sauna has already been purchased; it is a 2.1 x 2.1 m cabin, with walls and ceiling constructed in sandwich design (wood frame, insulation in between, and cladded on both sides with profile boards).

We have chosen our currently unused basement room (just under 30 sqm) as the installation location. The room offers enough space for the sauna, a few loungers, and possibly a shower which I might install at a later date. The basement room is unfortunately not heated (except for a wood stove), and here my mental struggle begins... warm moist air + cold walls = condensation.

Here are a few additional details regarding the room:
- As already mentioned, the room is just under 30 sqm, no radiators installed. Room height 2.20 m.
- The floor is tiled; I would like to lay a high-quality click vinyl floor on top, as I think this is much more comfortable than the cold tiles.
- The walls are plastered and painted.
- The room has a small basement window that can be tilted (30 x 60 cm).
- The room has a core drill hole into the chimney so that I can install a wood stove.

Here are some details about the sauna:
- External dimensions 2.1 x 2.1 m; 2.05 m high.
- 9 kW stove with Saunarium function (a kind of steam bath with relatively high humidity of about 50-60%).
- Sandwich design.

My questions are as follows:
I will leave a 10 cm gap all around between the sauna and the outer walls so that air can circulate. Should I additionally install a fan or something similar here to ensure that the air actually circulates?
Do I need to insulate the outer walls somehow?
To remove the warm and moist air from the sauna room, I thought about a timer-controlled fan (installed in the window) which runs for a certain time after sauna use.
Additionally, I would place an electronic dehumidifier in the room to sustainably maintain low humidity.

I would light the wood stove 2-3 hours before sauna use so that the walls would warm up somewhat. The wood stove has a 120 kg heat storage mass, so it stores heat over several hours and only cools down gradually; therefore, the room temperature would also cool down gradually, which in my opinion is advantageous.

What do you think about my plan?
What would you recommend, what have I forgotten, and where am I completely wrong?

Thanks in advance

You have already thought of everything.
If the sauna room is open to the other rooms in the basement, the heated air spreads quite quickly throughout the basement.
That means your mirror, or whatever else, fogs up when opening the sauna for 10 minutes. After that, everything is dry again.
More humidity forms when showering than when using the sauna.
The distance to the exterior walls is important. Circulation happens automatically. As a precaution, check visually from time to time.
If no insulated plastic window is installed, leave it slightly open after sauna use to prevent condensation from forming.
A wood stove in the sauna area is highly recommended. You cool down quite quickly otherwise.

Actually, when determining property tax, one must indicate that they have a sauna. The property tax increases as a result. Many forget this for some reason.

You've already thought of everything. If the sauna room is open to the other rooms in the basement, the heated air spreads quite quickly throughout the basement. That means your mirror, or whatever else, will fog up when you open the sauna for 10 minutes. After that, everything is dry again. More humidity forms when showering than when using the sauna. The distance to the exterior walls is important. Circulation happens on its own. For safety, conduct occasional visual checks. If no insulated plastic window is installed, leave it slightly open after using the sauna so that no condensation forms there. A wood stove in the sauna area is highly recommended. You cool down quite quickly.

Actually, when determining property tax, you have to indicate that you have a sauna. The property tax increases because of this. Many forget this for some reason.

Thanks for the reply. The thing about the property tax was indeed unknown to me... I need to read up a bit on this topic.

May I ask where you ordered your sauna? The dimensions would also fit quite well in our basement. Similar conditions, but with a radiator in the room.

May I ask where you ordered your sauna? The dimensions would also fit quite well in our basement.

Similar conditions, but with a radiator in the room.

Hello,

It is a Klafs sauna.
I got it as an unused display model for a fraction of the original price. It was a custom sauna, so not a standard product... I was lucky and the size fit perfectly in my basement.