Outdoor sauna ventilation: basic requirements to follow

When designing a long-lasting sauna that gives good steam, you must take some basic rules into account.

In a poorly designed sauna, the temperatures at different levels vary too much. It can be too cold on the floor and too hot at head height.

The reason for a poor sauna experience is often insufficient ventilation of the steam room. Ventilation brings oxygen to the wood-burning and the air circulation of the electric heater. Thanks to this, there is enough oxygen-rich air to breathe, and it removes sweaty exhaust air from the sauna.

The air in the sauna should be changed at least 3-5 times an hour. Poorly ventilated saunas are more likely to suffer from excessive carbon dioxide, making you feel tired pretty quickly. A good amount of carbon dioxide in the air is considered to be less than 600 ppm or 0.06%.

Outdoor Sauna ventilation requirements

Ventilation can be either gravity or mechanical, depending on the heater type, room design, and location. Mechanical ventilation is usually used in indoor saunas or non-traditional locations, such as basements, and it often needs expert planning.

In this article, we focus on gravity ventilation that works best for Finnish-style outdoor saunas and is very easy to implement.

Venting a wood-burning Finnish sauna

BZB Igloo sauna

The gravity ventilation is based on the warm air rising upwards. Fresh air is taken close to the heater and the floor, and heated air rises upwards and leaves through the ceiling’s outlet vent. The most traditional way for fresh air supply is from under the door, through about a 4-inch high door cap.

The outlet vent should be located in the ceiling or about 6 inches from the ceiling level, opposite the heater, and should be adjustable so you can control the air circulation.

This method works well for wood-burning saunas, but it’s inefficient and not generally recommended for electric heaters.

Electric sauna ventilation

In a sauna with an electric heater, the intake vent should be above the heater, about 20 inches from the upper stones or as specified in the installation manual. The outlet vent should be as far away from the heater as possible, ideally located under the sauna bench, just below the sauna bather’s feet.

The second outlet vent should be in the ceiling or about 6 inches from the ceiling level, intended for removing hot and damp air after sauna bathing. This vent can be closed during steam sessions.

Keep an eye on the temp sensor location!

If your electric heater is equipped with a separate temperature sensor mounted on the wall or ceiling, make sure the intake vent is not within its range. The supply air cools the sensor, giving the heater incorrect information about the sauna temperature, and may put you in danger.

Install the sensor in the place specified in the heater’s installation instructions to work correctly and safely.

Ideal sauna temperature

Temperature affects the humidity and oxygen content of the air. Finnish sauna experts say that it is good to breathe in the sauna and enjoy the steam when the temperature is below 158°F, and the humidity is about 40 percent.

Good luck with your sauna-building journey, and let us know if you need any help. Happy saunaing!


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