Ventilation

The sauna is about hot air and keeping it hot. But you also need oxygen-rich fresh air. Without it, your woodburning stove would not sustain fire and you would soon become tired with the lack of oxygen. The air circulation needs to be very slow, though. Most saunas have some sort of an air-circulation characteristic. The objective is to get enough fresh air coming in for people to breathe and enough oxygen to keep wood-burning stove burning.

The number one thing to judge the ventilation of a sauna, is the correct balance among these factors:

1.  the air has to stay fresh enough

2. the stove needs to have enough air to burn

3. the sauna cannot lose a lot of temperature

4. the sauna should not get drafty

To reduce the amount of air needed, you can place the loading side of the stove outside the hot room, to minimize the amount of ventilation to keeping the stove burning. Or you can draw the air you need for burning logs in from alternative sources, without circulating it in the hot room.

Most of the saunas I have seen are with natural, not forced ventilation. Air is drawn in from under the door (not directly from outside) and then released from venting holes or through the stove.

When building a sauna, you need an intake vent and exhaust vent of the same size. You can have a natural or mechanical ventilation system.