The Cozy Heat O Through-Wall Sauna Stove Package combines two of the most distinctive elements in the Cozy Heat range: the circular rim design of the Cozy O and the through-wall installation of the Cozy Through-Wall. The result is a complete wood-burning sauna stove package where the rounded, organic form of the O sits inside the sauna room with its stone mass visible within the circular rim, while its firebox passes through the sauna wall so that wood is loaded, fire is tended, and ash is removed entirely from outside the sauna. The sauna interior stays clean and undisturbed. The bathers stay in session without interruption. The stove body presents a soft, rounded silhouette in the sauna room rather than the angular lines of the standard Through-Wall. Available in 12kW (210-423 cu ft) and 18kW (317-635 cu ft) with stone style selected at checkout, and complete with sauna stones included.
The O design with through-wall installation - combining form and function
The Cozy O Through-Wall is the only model in the Cozy range that offers both the circular rim design and external firebox loading in a single unit. The Cozy O (without through-wall) sits inside the sauna room and loads from inside. The Cozy Through-Wall (without the O design) passes through the wall with a conventional stove body form. The O Through-Wall combines them: the circular rim with its soft, rounded stone presentation faces the sauna interior, the firebox passes through the wall, and all fire management happens on the exterior side. For sauna room designs built around organic, rounded, or natural material aesthetics where the stove should appear as a soft rounded element within the space - and where the sauna building layout allows through-wall installation - the O Through-Wall is the specific model that serves both requirements simultaneously.
Through-wall firebox loading - what it changes operationally
In every Cozy model without through-wall installation, wood is loaded through a firebox door that faces into the sauna room. The bather or attendant must enter the hot room to tend the fire. In the O Through-Wall, the firebox opening is on the exterior side of the sauna wall - in the changing room, a utility corridor, or outside. Wood can be loaded while bathers are in session. Ash can be removed without entering the sauna. No wood chips, bark, or ash fall onto the sauna floor during loading. No smoke enters the room when the firebox door is opened. This is the traditional Nordic and Baltic installation method where the bathing chamber and the stoke-hole are intentionally separated - a design that treats the sauna interior as a clean, undisturbed space for bathing, and keeps all the operational work of fire management entirely outside it.
Same Cozy Heat engineering - circular rim, external loading, full performance
The O Through-Wall carries every technical specification of the Cozy Heat range: 5mm stainless flame cutter, three-stage combustion system with primary, secondary, and tertiary air injection, 25-40% firewood reduction, and 73.9% or 81.3% thermal efficiency at 12kW and 18kW respectively. German BlmSchV DIN EN 13240 Level 2 and EN 15821:2010 certification apply. A chimney installation is required and sold separately. The wall penetration must be correctly sized and fire-protected, and the installation must be carried out by a qualified professional. This is a more involved installation than any of the conventional floor-standing Cozy models - both the through-wall configuration and the chimney must be planned before the stove is ordered.
Wood-burning sauna stove package combining circular rim design with through-wall installation - available in 12kW (210-423 cu ft) and 18kW (317-635 cu ft), select at checkout. Includes Cozy O Through-Wall stove and sauna stones (stone style selected at checkout). Circular rim stone presentation inside sauna room. Firebox passes through sauna wall - wood loaded, fire tended, ash removed from outside. Clean sauna interior, bathers undisturbed during session. 5mm stainless steel flame cutter. Three-stage combustion - 25-40% less firewood. EN 15821:2010 and German BlmSchV DIN EN 13240 Level 2 certified. 12kW: 73.9% efficiency. 18kW: 81.3% efficiency. No electrical required. Chimney required - sold separately. Wall penetration installation required - by qualified professional. Handmade in Estonia. 2-year warranty.
Package - stove + stones included Circular rim design + through-wall installation 12kW (210-423 cu ft) or 18kW (317-635 cu ft) Circular rim stone presentation inside sauna Firebox from outside - clean interior Wood loaded without entering sauna room Three-stage combustion 25-40% less firewood than comparable stoves 5mm stainless steel flame cutter EN 15821:2010 certified German BlmSchV DIN EN 13240 Level 2 Chimney required - sold separately Handmade in Estonia 2-year warranty
Specifications
Output selection - choose at checkout
| 12kW |
210 to 423 cu ft | Min 265 lbs stones | 73.9% efficiency |
| 18kW |
317 to 635 cu ft | Min 353 lbs stones | 81.3% efficiency |
| Electrical required |
None |
| Chimney required |
Yes - sold separately |
| Stone style |
Selected at checkout |
Design, installation and combustion
| Design feature |
Circular rim - rounded form, soft organic presentation |
| Installation type |
Through-wall - firebox on exterior side of sauna wall |
| Stone mass location |
Inside sauna room - circular rim visible |
| Firebox door location |
Outside sauna room |
| Combustion stages |
Three-stage: primary, secondary, tertiary |
| Firewood reduction |
25-40% less than comparable stoves |
| Certification |
EN 15821:2010 | BlmSchV DIN EN 13240 Level 2 |
Firebox opening dimensions
| 12kW minimum opening width |
10.0" (255 mm) |
| 12kW minimum floor height |
17.3" (440 mm) |
| 18kW minimum opening width |
12.4" (315 mm) |
| 18kW minimum floor height |
18.5" (470 mm) |
Construction
| Design |
Circular rim - rounded stone presentation |
| Flame cutter material |
5mm stainless steel |
| Body construction |
Steel |
| Flue outlet position |
Top of stove |
| Origin |
Handmade in Estonia |
Installation requirements
| Wall penetration |
Required - correctly sized and fire-protected |
| Adjacent space required |
Yes - on exterior firebox side of sauna wall |
| Chimney |
Required - sold separately |
| Professional installation |
Required |
| Shared flue system |
Not suitable |
| Firewood |
Dry seasoned hardwood required |
Warranty
| Warranty period |
2 years |
| Overfiring |
Not covered |
| Chimney sweeping |
Required regularly |
What's included
Cozy Heat O Through-Wall wood-burning sauna stove (12kW or 18kW - selected at checkout)
Sauna stones - style selected at checkout (min 265 lbs / 12kW, min 353 lbs / 18kW)
Installation and operation manual
Not included (required for operation): Chimney and flue pipe installation (sold separately); wall penetration installation materials and labour (by qualified professional). Optional: Additional sauna stones.
Why the Cozy Heat O Through-Wall Package stands out
Circular rim inside, firebox outside
The only Cozy model that combines the O's circular rim stone presentation with through-wall external firebox loading. The rounded stone mass is visible in the sauna room within its circular border; the firebox passes through the wall and all fire management happens outside. The specific model for buyers who want both features together.
Soft rounded form for organic interiors
The circular rim brings the Cozy O's softer, organic visual quality to the through-wall installation format. For sauna rooms with rounded or natural design elements - curved bench ends, natural stone or tile surfaces, organic material palettes - the O Through-Wall integrates more naturally than the standard Through-Wall's conventional body form.
Clean interior - bathers undisturbed
Wood loaded, fire tended, and ash removed from outside the sauna room. The session is not interrupted by fire management. No wood chips, bark, ash, or smoke inside the sauna. The most operationally clean of all wood-fired sauna installations - and now available with the O's circular rim design visible from inside.
Traditional Nordic installation method
Through-wall firebox loading is the oldest and most traditional installation in Nordic and Baltic sauna culture - the design that separated the bathing chamber from the stoke-hole in the original Finnish and Estonian smoke saunas. The O Through-Wall brings this traditional functional arrangement together with one of Cozy Heat's most contemporary design forms.
Three-stage combustion - 25-40% less firewood
Primary, secondary, and tertiary air injection - 73.9% efficiency at 12kW, 81.3% at 18kW, up to 6x cleaner smoke gases. Certified to Germany's BlmSchV DIN EN 13240 Level 2 and EN 15821:2010. Identical combustion performance to every other Cozy Heat model.
Professional installation required
The wall penetration must be correctly sized and fire-protected by a qualified professional. A chimney must be installed separately. An accessible adjacent space on the exterior side of the sauna wall is required. Plan and engage an installer before ordering - confirm the building layout supports through-wall installation.
About Cozy Heat
Handmade in Estonia - circular rim, external loading
Cozy Heat O Through-Wall. The O's rounded form combined with the traditional external firebox installation.
Cozy Heat is an Estonian sauna stove manufacturer. The O Through-Wall is for buyers who want two things at once: the soft, organic circular rim design of the Cozy O visible inside the sauna room, and the clean, undisturbed sauna interior that through-wall firebox loading provides. Every technical specification is identical to the rest of the Cozy range - the 5mm stainless flame cutter, three-stage combustion, and German EN 15821:2010 certification all apply. The O Through-Wall is the correct model when both the design and the installation method matter to the buyer.
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Complete package - Cozy O Through-Wall stove and stones (style at checkout)
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Circular rim inside sauna, firebox outside - the O design with external loading
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12kW (210-423 cu ft) or 18kW (317-635 cu ft) - select at checkout
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Three-stage combustion - 25-40% less firewood, EN 15821:2010 certified
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Professional wall installation required - plan before purchasing
O Through-Wall vs its alternatives
Choosing between the O Through-Wall and its nearest alternatives
Cozy O PKG (SKU 129776): circular rim design, inside-loading firebox - for buyers who want the O's rounded form but load from inside the sauna. Cozy Through-Wall PKG (SKU 129792): through-wall external loading, conventional stove body - for buyers who want external loading but without the circular rim design. Cozy O Through-Wall PKG (this listing): circular rim inside the sauna, firebox through the wall - the specific choice when both features are wanted together and the building layout supports it. All three share identical technical performance, output levels, stone requirements, certifications, and warranty.
A chimney and correctly installed wall penetration are required. Use only dry, seasoned hardwood. Do not overfire. Sweep the chimney regularly. A qualified professional must carry out the wall and chimney installation.
Manuals and Documents
Warranty
2-year warranty
The Cozy Heat O Through-Wall Sauna Stove is covered by a 2-year limited warranty from the date of purchase. The warranty covers defects in manufacturing and materials under normal use conditions. The warranty does not cover: damage caused by overfiring; failure to use dry, seasoned firewood; failure to regularly sweep the chimney; failure to follow installation requirements including proper wall penetration and chimney installation by a qualified professional; or improper modification of the stove. Proof of purchase from an authorized Cozy Heat dealer is required. We are an authorized Cozy Heat dealer.
