The sauna is located in the main building and is both nice and fresh.
To use the sauna you need to book it, it is done on site.
If the sauna is cold, it takes about 45 minutes to get it up to the right temperature. You can start it yourself or ask someone on the staff to start it for you in advance.
The sauna costs SEK 100 for an hour.
If you want to take a bath and do not staying at Fulufjällsgården, it is also fine. Then it costs SEK 100 plus SEK 30 per person.