The biggest problem is having the same volume of ventilation before, during and after sauna bathing. The need for ventilation is largest during intense sauna-bathing. The intense sauna-bathing with a lot of löyly requires, that the sauna must always dry out after bathing.

The rules and guidelines concerning the ventilation of a sauna trace back to a time, when the saunas were heated with fire. Without the fire, the suggested volumes are often too large.

An exhaust vent in the ceiling sized to the old guidelines is absurd. It makes no sense to channel the hot air rising from the stove directly to the magpies. When the sauna is sensibly ventilated, the need for air changes is much smaller than suggested by these guidelines. It is worth experimenting to attain a suitable level for ventilation.

If there is a wood-burning type ventilation in the sauna, i.e. air intake is behind the heater and exhaust is in the ceiling or up on the wall, a good solution is to make the exhaust vent adjustable. This vent hould be closed during the heating up and be open during and after sauna-bathing. By keeping the vent closed the sauna heats up much faster, because there is no heat going away with ventilation.

Click to see this image bigger... When taking löyly the vent should be wide open, which forces the fresh air to rise up also past the stove. As the exhaust is open only when there are bathers in the sauna, there is not much excess energy consumption and still there is enough fresh air.

This adjustable exhaust vent shortens the time for heating up sauna and lessens the need for heating effect. This is a good solution, when there is no need to keep sauna hot but empty. If the sauna is hot but empty long time, the stones of the heater may loose their ability to give löyly as described in chapter How the Heaters and Stoves Work.

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