How to Heat a Wood-Fired Sauna, and How Long It Takes
Most wood-fired saunas take somewhere between 45 minutes and an hour and a half to get to bathing temperature. Exactly how long depends on your stove, your room and the weather.
How long it takes
A well-matched wood stove usually brings a sauna to 70–80 °C (160–175 °F) in about 45–90 minutes. Expect the long end, or longer, when:
- It's cold outside, and the room, walls and stones start cold
- The stove is small for the room's volume, or the room is poorly insulated
- The wood is damp or split too thick
- The stove holds a lot of stones, which take longer to heat (and then hold heat longer)
A winter heat-up can easily take half an hour longer than a summer one in the same sauna.
Ready is more than the thermometer
The air heats faster than the stones and walls. When the thermometer first reads your target, giving it another 15–20 minutes lets the stones catch up, so the steam (löyly) is soft and steady rather than flat. Read the thermometer at about head height above the upper bench, away from the stove; that's the temperature you'll actually sit in.
Lighting and feeding the stove
- Open the damper and any air intake, and clear old ash if your stove needs it.
- Use dry, seasoned hardwood split fairly small. Dry wood burns hotter and cleaner than wet wood.
- Light a small, fast fire with kindling, then add larger pieces once it's going well.
- Feed it every 15–20 minutes, a few pieces at a time, to keep a lively flame rather than a smoldering one.
- Keep the sauna door closed while it heats.
Safety
- Follow your stove manufacturer's instructions and clearances.
- Make sure the room is ventilated, and keep a carbon monoxide alarm in or near the sauna building.
- Don't leave a fire burning unattended for long.
- Close the damper only once the fire has completely burned down, per your stove's instructions.
How Sauna Rounds helps
Tell Sauna Rounds when you want to be in the sauna, and it works back to when to light the stove, using your local weather. As you record heat-ups, its estimates learn how your particular sauna behaves. It never controls the stove; it just tells you when to start and how the heat-up is going.