Common sizes
Barrels are sold by outside diameter (usually about 1.8–2.2 m) and length (from about 1.5 m for two people to 4 m or more with a changing room). In North America the length is usually given in feet. The table shows common inside sizes with the seats, the effective volume a heater has to cope with, the electric heaters in our catalog rated for it and the heat-up time on a freezing day.
| Size (inside) | Seats | Effective volume | Heaters that fit | Heat-up at 32 °F |
|---|---|---|---|---|
| Ø 5.9 ft × 4.9 ft | 3 | 225 ft³ | 4.5–10.5 kW | 25–35 min (6 kW) |
| Ø 5.9 ft × 7.9 ft | 6 | 340 ft³ | 7.5–10.5 kW | 25–30 min (8 kW) |
| Ø 6.6 ft × 7.9 ft | 6 | 419 ft³ | 8–13 kW | 35–45 min (10.5 kW) |
| Ø 6.6 ft × 9.8 ft | 8 | 514 ft³ | 10.5–15.2 kW | 80–110 min (12 kW) |
| Ø 6.6 ft × 13.1 ft | 11 | 673 ft³ | 15–18 kW | 70–95 min (15 kW) |
Inside sizes. Effective volume follows Harvia's rule for solid wood walls (× 1.5). Heat-up with the heater whose range best centres on the room (its output in brackets), 32 °F outside, to 176 °F at the ceiling: our heat model, as a range.
A porch or changing section at the front shortens the hot room: compare the hot room's own length, not the barrel's.
Why barrels need a bigger heater than their volume suggests
A barrel's walls are solid wood staves, typically 40–45 mm thick, without insulation. Heater makers count solid wood walls as 1.5 × the room's volume (Harvia's rule, which our calculator uses), so a barrel with 5 m³ of air needs a heater rated for about 7.5 m³. In our heat model a correctly sized barrel then heats about as fast as an insulated cabin with a similar floor: the round shape has less air to heat, while the uninsulated staves lose more heat through the walls, which shows on the coldest days.
Electric or wood
- Electric heaters of 6–9 kW cover most two- to six-person barrels; check the maker's room range against the effective volume, not the air volume. See sauna heaters.
- Wood stoves suit barrels without a power line; through-wall stoves are fired from the changing room or outside. See wood-burning sauna stoves.
What to check before you buy
- Wood and thickness: spruce, pine, thermowood and cedar are common; thicker staves hold heat better and warp less.
- Bands: stainless steel bands that you can re-tighten as the wood moves with the seasons.
- Roof: shingles, a membrane or a metal roof over the staves protects them from rain and sun.
- Door: glass looks open but adds effective volume (see sauna doors).
- Benches: the upper bench about 1.0–1.2 m below the highest point; see bench height.
- Heater included? Check its maker's room range against the barrel's effective volume.
Base and assembly
Barrels sit on two or more cradles, so they need a level, well-drained base: compacted gravel with paving slabs, concrete pads or a timber deck. Leave airflow under the barrel and a way for water to drain.
Compare the shape with a cabin in barrel vs cabin sauna, or build a barrel at your size in the 3D studio.