The best mixing of the hot air rising up from the stove and the cool incoming air can be obtained when the fresh air is blown into the sauna through the ceiling just above the stove. When the falling heavy cold air becomes mixed with the rising light air, it brings fresh air to the bathers to breathe and cools also the hot air rising from the stove.
The incoming fresh air is the heaviest air in the sauna. If it comes in anywhere but above the stove, it is only a nuisance. It falls directly to the floor, and spreads out on the floor. There is an up-flow of air through the stove and only that small amount of fresh air that rises through the stove, freshens the breathing air. The cool air that spreads on the floor, increases the temperature differential between the upper and lower parts of the sauna. It causes a drag, and spreads out under the door in to the washing room and cools the floor there. The cool air increases humidity and, at worst, can create mould.
If the fresh air is blown into the sauna and the intake happens to be behind the stove, it is worth the effort to channel the air with a pipe to at least 0,5 meter above the stove. In general, it is easier to channel the incoming air trough the ceiling than through the wall. If this is not possible, it is beneficial to channel the incoming air to the stove, and limit its amount to that rising up through the stove in order to avoid excess cool air from spreading on the floor.
© SaunaSite, 1997