Find the right fire door, room range, and stone-cage shape

How to Choose a Cozy Heat Wood-Burning Sauna Stove

You do not need to memorize twenty model names. Start with the adjusted volume of the finished sauna, decide whether you want to tend the fire inside the hot room or through the wall, then choose the cage shape you want to live with. We have checked the current manual and exact drawings so every path below leads to a real 12 or 18 kW heater.

Fast sizing: COZY 12 models cover 212–424 cu ft; COZY 18 models cover 318–636 cu ft. Use the finished inside dimensions. Add about 4 cu ft for every square foot of glass, tile, brick, concrete, or other uninsulated surface, and multiply a massive-log room by 1.5. Between sizes? Call before ordering instead of guessing.

1. Decide where you want to tend the fire

An in-room model keeps the flame and wood-loading ritual inside the sauna. A Thru-Wall model passes through a properly built noncombustible opening so the fire door, ash, and active woodpile can stay in the adjoining room. That choice affects the wall plan, so make it before the room is finished.

2. Choose the shape you want to see every session

Cozy Heat Standard 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
Standard: 12 and 18 kW, in-room loading.

Cozy Heat Thru-Wall 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
Thru-Wall: 12 and 18 kW, through-wall.

Cozy Heat O 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
O: 12 and 18 kW, in-room loading.

Cozy Heat O Thru-Wall 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
O Thru-Wall: 12 and 18 kW, through-wall.

Cozy Heat Og 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
OG: 12 and 18 kW, in-room loading.

Cozy Heat Og Thru-Wall 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
OG Thru-Wall: 12 and 18 kW, through-wall.

Cozy Heat Sw 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
SW: 12 and 18 kW, in-room loading.

Cozy Heat Sw Thru-Wall 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
SW Thru-Wall: 12 and 18 kW, through-wall.

Cozy Heat Quattro 12 And 18 Wood-Burning Sauna Stoves Together On Black Wood Cladding.
Quattro: 12 and 18 kW, in-room loading.

Cozy Heat Quattro Thru-Wall 12 And 18 Wood-Burning Sauna Stove Options Shown Together.
Quattro Thru-Wall: 12 and 18 kW, through-wall.

3. Compare the exact 12 and 18 kW models

On a phone, swipe the table sideways to compare every column.

Family 12 kW 18 kW Firewood loading
Standard
The original open-mesh COZY profile for an all-around traditional wood-sauna installation.		 16.9 × 20.1 × 27.6 in
243 lb stones		 19.7 × 24.6 × 29.8 in
353 lb stones		 Inside sauna
Thru-Wall
The original open-mesh stone cage with an extended firebox so wood can be loaded from the adjoining room.		 16.9 × 26.0 × 27.6 in
243 lb stones		 19.7 × 30.5 × 29.8 in
353 lb stones		 Adjoining room
O
The smooth round O jacket gives the classic COZY firebox a cleaner cylindrical exterior.		 17.7 × 20.5 × 27.6 in
243 lb stones		 19.9 × 24.8 × 29.8 in
353 lb stones		 Inside sauna
O Thru-Wall
The cylindrical O exterior with an extended firebox for loading from outside the hot room.		 17.7 × 26.4 × 27.6 in
243 lb stones		 19.9 × 30.7 × 29.8 in
353 lb stones		 Adjoining room
OG
A sculpted round cage with more visible stone surface and a distinctive flared silhouette.		 19.6 × 21.5 × 27.9 in
265 lb stones		 22.0 × 25.8 × 29.7 in
353 lb stones		 Inside sauna
OG Thru-Wall
The sculpted OG stone cage paired with a through-wall firebox extension.		 19.6 × 27.4 × 27.9 in
265 lb stones		 22.0 × 31.7 × 29.7 in
353 lb stones		 Adjoining room
SW
A taller wave-pattern cage that exposes a broad field of stones and carries the largest 18-family stone mass.		 19.3 × 21.3 × 32.1 in
265 lb stones		 21.7 × 25.6 × 34.3 in
397 lb stones		 Inside sauna
SW Thru-Wall
The tall wave-pattern stone cage with an extended firebox for loading from the adjoining room.		 19.3 × 27.2 × 32.1 in
265 lb stones		 21.7 × 31.5 × 34.3 in
397 lb stones		 Adjoining room
Quattro
A square four-sided stone cage for projects that prefer crisp geometry over a round profile.		 17.3 × 20.2 × 27.6 in
220 lb stones		 20.3 × 24.8 × 28.8 in
353 lb stones		 Inside sauna
Quattro Thru-Wall
The square Quattro cage with an extended firebox for loading from outside the sauna room.		 17.3 × 26.2 × 27.6 in
265 lb stones		 20.3 × 30.7 × 28.7 in
353 lb stones		 Adjoining room

Why Cozy feels different

Founder Voldemar Nellis learned stove craft beside his father, Paul, in rural Estonia before building Cozy around its own design, engineering, and production. The current heaters put 220–397 lb of exposed stone around a compact steel firebox. That stone reserve, more than a decorative jacket, is the heart of the soft, lingering steam Cozy is trying to make.

  • Three-path combustion air, including secondary air above the fuel.
  • A glass firebox door and an open stone field across all ten families.
  • 12 Pa required draft and 12.2 sq in minimum smoke-flue cross-section.
  • Current EN 15821:2010 and BImSchV Stage 2 test documentation.
  • 24-month limited U.S. warranty with proof of purchase; read the current warranty for exclusions.

The efficiency claim, kept in proportion

Cozy currently says its combustion design uses about 25% less wood than comparable heaters. Its 40% figure was reached only in ideal tests, so we do not present that as the everyday promise. The current manual reports 73.9% efficiency for the 12 family and 81.3% for the 18 family.

Installation facts that change the project

  • Combustible side clearance: 6.7 in for 12; 9.1 in for 18.
  • Rear clearance: 9.1 in. Front clearance: 19.7 in.
  • Clearance above the stove: 44.5 in for 12; 52.8 in for 18.
  • TW wall thickness: up to 5.9 in, with the exact wall opening and protection built to the manual.
  • First burn: outdoors or well ventilated, without stones, so the coating cures safely.
  • Fuel: dry natural firewood only; maximum log length is 13.0 in for 12 and 15.7 in for 18.

Stones, chimney, and package choices

Current exact-model drawings call for 220–265 lb of stone in the 12 family and 353–397 lb in the 18 family. Heater-only listings do not include stones or a chimney. Package listings pair one exact heater with a stated box count of split-face or rounded olivine diabase stones. Chimney covers can add another 44–132 lb of stone around the exposed flue, depending on the model. Follow the stone size and loose-loading directions in the manual supplied with the heater.

See Cozy in real rooms

Cozy 12 Wood Sauna Stove Installed In A Sauna
Cozy 12 wood sauna stove installed in a sauna
Cozy 12 Wood Stove Installation Detail
Cozy 12 wood stove installation detail
Cozy Quattro 12 Installed In A Wood Sauna
Cozy Quattro 12 installed in a wood sauna
Cozy Quattro Wood Sauna Stove Installation
Cozy Quattro wood sauna stove installation
Cozy Sw 12 Installed With Its Wave Stone Cage
Cozy SW 12 installed with its wave stone cage
Cozy Sw 18 Wood-Burning Sauna Stove Installation
Cozy SW 18 wood-burning sauna stove installation
Cozy Og 18 Installed In A Sauna
Cozy OG 18 installed in a sauna
Wood Fire Visible Through A Cozy Sauna Stove Glass Door
Wood fire visible through a Cozy sauna stove glass door

Current manuals, drawings, and warranty

Use these files for installation and product decisions. The exact 12 and 18 drawings are also attached to their matching family pages.

Older marketing archive

Cozy’s latest supplied marketing package includes a brochure created in October 2024 and a presentation created in February 2024. They are useful for the founder story and visual language, but their specifications, finish availability, warranty, and model lineup are not current. The July 2026 manual, exact drawings, current product pages, and current U.S. warranty take priority.

Finish availability

The current U.S. assortment is black steel. Cozy’s global photography also shows stainless cages, but stainless is not treated as a selectable U.S. variation unless the exact listing says so.

Want us to check the decision before you buy?

Send the finished inside dimensions, ceiling height, wall construction, glass or masonry area, chimney plan, and preferred loading side. Call or text (844) 565-1113 and we will help match the room to the right family, size, stones, and installation documents.