Heat and humidity
| Sauna | Steam room | |
|---|---|---|
| Air temperature | about 70–100 °C at the ceiling | about 40–50 °C |
| Humidity | dry between throws; löyly adds short bursts | close to saturation, the room is foggy |
| Heat source | heater with stones (electric or wood) | steam generator, usually outside the room |
| Surfaces | wood that stays comfortable to touch | tile, glass, stone or acrylic |
| Where it can go | indoors or in the garden | indoors, usually in or next to a bathroom |
Tylö's steam room manual, for example, describes holding the room at 40–50 °C.
Why a steam room feels as hot
Your body cools itself by sweating. In a sauna's dry air the sweat evaporates and carries heat away; in a steam room the air is already saturated, so it can't, and steam even condenses on your skin, releasing heat. Air at 45 °C holds at most about 65 g of water per cubic metre; air at 80 °C can hold more than four times as much, which is why a sauna stays comfortable between throws.
Building one at home
- Sauna: carpentry, insulation, a foil vapour barrier and wood panelling (how to build a sauna); electric heater or wood stove; can stand outdoors.
- Steam room: a fully waterproof enclosure (tanked walls, tiles or acrylic), a sloped ceiling so drips run down the walls, a floor drain, a door that seals, and a steam generator sized for the room. Often built as a steam shower in a bathroom.
Running cost
A sauna heats the air, the stones and the wood each time; the sauna running cost calculator shows the cost per session. A steam room's generator boils water while the room is in use and warms tiled surfaces that take a while to heat.
Which suits you
If you want garden bathing, löyly and the option of wood heat, a sauna. If you are converting a bathroom and like gentle, humid heat, a steam room or steam shower. Many spas have both.