The Cozy Heat OG Through-Wall Sauna Stove Package combines the contemporary trilateral design of the Cozy OG with through-wall installation - the refined three-sided body with clean lines and graceful curves faces the sauna interior, while the firebox passes through the sauna wall so that wood is loaded, fire is tended, and ash is removed entirely from outside the sauna room. The sauna interior stays clean and the session undisturbed. Available in 12kW (210-423 cu ft) and 18kW (317-635 cu ft) with stone style selected at checkout, complete with stones included. The OG Through-Wall is the specific model for buyers who want the most refined version of the trilateral three-sided Cozy form combined with the operational advantages of through-wall external firebox loading.
The OG design with through-wall installation
The Cozy OG body is the contemporary trilateral variant - three sides with clean lines and graceful curves that refine the base Cozy's more angular geometry into a more design-forward, polished form. In the OG Through-Wall, this body faces the sauna interior: the three-sided curved form with its stone mass is the visible element in the bathing room, while the firebox opening passes through the sauna wall to an adjacent space on the exterior side. Wood loading, fire management, and ash removal all happen outside the sauna without disturbing the session. For sauna rooms designed around a contemporary aesthetic where the stove body's refined trilateral curves should be visible from inside, and where the sauna building layout supports through-wall installation, the OG Through-Wall is the model that satisfies both requirements simultaneously.
Through-wall operation - clean sauna, undisturbed session
In all conventional inside-loading Cozy models, fire management requires entering the hot sauna room. In the OG Through-Wall, the firebox door is on the exterior side of the sauna wall - in the changing room, a utility corridor, or outdoors. Wood is loaded from outside. The fire is tended from outside. Ash is removed from outside. No wood chips, bark, or ash on the sauna floor. No smoke entering the room when the firebox door opens. The session continues without interruption. This is the traditional Nordic and Baltic installation method that kept the bathing chamber as a clean, uninterrupted space for bathing and separated all the operational work of fire management to a dedicated exterior space. The OG Through-Wall brings this traditional functional principle together with Cozy Heat's most refined trilateral design form.
Same Cozy Heat engineering throughout
Every technical specification of the Cozy Heat range applies: 5mm stainless steel flame cutter, three-stage combustion (primary air through the grate, secondary through mid-chamber channels, tertiary through ceiling pipes burning the flue gases as a third combustion stage), 25-40% firewood reduction, 73.9% efficiency at 12kW and 81.3% at 18kW, and German BlmSchV DIN EN 13240 Level 2 and EN 15821:2010 certification. A chimney installation is required and sold separately. The wall penetration must be correctly sized and fire-protected, and the full installation must be carried out by a qualified professional. Confirm the sauna building layout supports through-wall installation before ordering.
Wood-burning sauna stove package combining contemporary trilateral design with through-wall installation - available in 12kW (210-423 cu ft) and 18kW (317-635 cu ft), select at checkout. Includes Cozy OG Through-Wall stove and sauna stones (stone style selected at checkout). Three-sided body with clean lines and graceful curves faces sauna interior. 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 Contemporary trilateral curves + through-wall 12kW (210-423 cu ft) or 18kW (317-635 cu ft) Refined three-sided form inside sauna Firebox from outside - clean interior Bathers undisturbed during session 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 |
Contemporary trilateral - clean lines with graceful curves |
| Installation type |
Through-wall - firebox on exterior side of sauna wall |
| Stone mass location |
Inside sauna room |
| 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 |
Contemporary trilateral - clean lines and graceful curves |
| 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 OG 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 OG Through-Wall Package stands out
Refined trilateral curves inside, firebox outside
The OG's contemporary three-sided body with clean lines and graceful curves faces the sauna interior - the most design-forward trilateral form in the Cozy range is the visible element in the bathing space. The firebox passes through the wall and all fire management happens outside. The specific model when both the OG design and through-wall loading are required.
Clean sauna interior, undisturbed session
Wood loaded, fire tended, and ash removed from outside without entering the sauna room. No wood, bark, ash, or smoke inside. The session is not interrupted by fire management. For sauna rooms where cleanliness and session continuity are priorities alongside design refinement, the OG Through-Wall delivers all three.
Traditional Nordic installation, refined form
Through-wall firebox loading is the oldest and most traditional installation in Nordic and Baltic sauna culture - the design that kept the bathing chamber separate from fire management. The OG Through-Wall pairs this traditional functional principle with Cozy Heat's most refined trilateral design: contemporary clean lines, not utilitarian angles.
Three-stage combustion - 25-40% less firewood
Primary, secondary, and tertiary air injection burns flue gases as a third combustion stage - 73.9% efficiency at 12kW, 81.3% at 18kW, up to 6x cleaner smoke gases. EN 15821:2010 and German BlmSchV DIN EN 13240 Level 2 certified. Identical combustion performance to every other Cozy Heat model.
5mm stainless flame cutter
The most thermally stressed part is fabricated from 5mm stainless steel across every Cozy Heat model - substantially heavier than industry standard. Resists warping and corrosion through years of firing cycles, extending stove service life well beyond lower-specification alternatives.
Professional installation required - plan first
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 firebox side is required. Confirm the building layout and engage an installer before ordering.
About Cozy Heat
Handmade in Estonia - refined trilateral, external loading
Cozy Heat OG Through-Wall. The most refined trilateral Cozy with the traditional external firebox installation.
Cozy Heat is an Estonian sauna stove manufacturer. The OG Through-Wall is for buyers who want two things simultaneously: the contemporary trilateral form with graceful curves visible in the sauna room, and the operationally clean through-wall installation where all fire management happens outside. The same 5mm stainless flame cutter, three-stage combustion, and German EN 15821:2010 certification as every Cozy model. The correct choice when both the OG's refined design and the Through-Wall's operational advantages matter and the building layout supports it.
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Complete package - Cozy OG Through-Wall stove and stones (style at checkout)
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Contemporary trilateral inside, firebox outside - refined design, clean operation
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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
OG Through-Wall vs its alternatives
Choosing between the OG Through-Wall and its nearest alternatives
Cozy OG PKG (SKU 129780): contemporary trilateral design, inside-loading firebox - for buyers who want the OG's refined 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 without the OG design. Cozy OG Through-Wall (this listing): contemporary trilateral design inside the sauna, firebox through the wall - the specific choice when both 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 OG 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.
