Cozy Heat Through-Wall Pkg Wood-Burning Sauna Stove Package, Up to 18kW
The Cozy Heat Through-Wall Sauna Stove Package is a complete wood-burning sauna stove package with a fundamentally different installation type from every other model in the Cozy range. Where the base Cozy, O, OG, SW, and Quattro all stand inside the sauna room with the firebox door facing the bathers, the Through-Wall stove is installed so that its firebox opening passes through the sauna wall - the stone mass and heat-radiating body sit inside the sauna room, while the firebox door faces the room or space outside the sauna wall. Wood is loaded from outside the sauna. The practical consequence is that wood loading, ash removal, and fire tending all happen without entering the sauna room, keeping the interior clean, smoke-free, and undisturbed during the session. This is the oldest and most traditional installation method for wood-fired saunas in Nordic and Baltic culture - the design that defined the Finnish smoke sauna and the Estonian heated chamber before modern stoves brought the firebox inside.
Through-wall installation - what it means and why it matters
In a conventional floor-standing sauna stove, the firebox door faces into the sauna room. To load wood, the bather or attendant must enter the sauna, open the door, load the logs, manage the fire, and remove ash - all from inside the hot room. In the Through-Wall installation, the stove body sits against the sauna wall with a purpose-built opening through the wall. The stone mass is inside the sauna where the heat and steam are needed. The firebox opening is on the other side of the wall - in the changing room, a utility corridor, or the outdoors. The person managing the fire never needs to enter the sauna room. Wood can be loaded while bathers are in session without interrupting them. Ash can be removed without entering the hot room. The sauna stays cleaner - no wood chips, bark, or ash on the floor, no smoke entering the room when the door is opened to load. For sauna buildings where the changing room or a utility space is adjacent to the sauna wall, the Through-Wall is a genuine operational upgrade over any conventional stove.
The same Cozy Heat performance - different where it matters for installation
The Through-Wall carries every technical specification of the Cozy Heat range. The flame cutter is 5mm stainless steel. The combustion system is three-stage: primary air through the grate, secondary air through the mid-chamber, and tertiary air through ceiling pipes that burn the flue gases as a third combustion stage. The result is 25-40% less firewood consumption than comparable stoves, up to 6x cleaner smoke gases, and 73.9% thermal efficiency at 12kW and 81.3% at 18kW. The German BlmSchV DIN EN 13240 Level 2 and EN 15821:2010 certification apply. A chimney installation is required and sold separately. The installation itself is more involved than a conventional floor-standing stove: the wall opening must be correctly sized and fire-protected, the stove body must bridge the wall correctly, and the chimney must exit from the appropriate position. This work must be done by a qualified professional.
12kW or 18kW - and the sauna rooms the Through-Wall serves
The 12kW Through-Wall covers rooms from 210 to 423 cubic feet with a minimum stone load of 265 lbs. The 18kW covers 317 to 635 cubic feet with a minimum of 353 lbs, the same specifications as every other Cozy Heat model at these output levels. Cozy Heat describes the Through-Wall as "perfect for intimate sauna rooms" - which reflects the practical reality that the through-wall installation requires a wall shared between the sauna and an adjacent space, which is more commonly available in purpose-built sauna cabins and traditional sauna buildings than in converted interior rooms. The Through-Wall is the correct choice when the sauna building design allows or specifically calls for firebox-exterior installation.
Wood-burning sauna stove package with through-wall installation - firebox feeds from outside the sauna room. Available in 12kW (210-423 cu ft) and 18kW (317-635 cu ft), select at checkout. Includes Through-Wall stove and sauna stones (stone style selected at checkout). Stone mass inside sauna room - firebox door on exterior side of wall. Load wood, tend fire, and remove ash from outside the sauna without disturbing bathers. Clean sauna interior - no wood, bark, ash, or smoke inside. 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 Through-wall installation - firebox from outside 12kW (210-423 cu ft) or 18kW (317-635 cu ft) Wood loaded from outside sauna - clean interior Fire tended without entering sauna room No wood, ash, or smoke inside sauna 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 |
Installation type and combustion
| Installation type |
Through-wall - firebox on exterior side of sauna wall |
| Stone mass location |
Inside sauna room |
| Firebox door location |
Outside sauna room (adjacent space or exterior) |
| Combustion stages |
Three-stage: primary (grate), secondary (mid-chamber), tertiary (ceiling pipes) |
| 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
| Distinguishing feature |
Through-wall - firebox passes through sauna wall |
| 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 opening through sauna wall |
| Adjacent space required |
Yes - changing room, corridor, or exterior on firebox side |
| Chimney |
Required - sold separately |
| Professional installation |
Required - more complex than conventional stove installation |
| Shared flue system |
Not suitable |
| Firewood |
Dry seasoned hardwood required |
Warranty
| Warranty period |
2 years |
| Overfiring |
Not covered - do not overload or leave controls fully open |
| Chimney sweeping |
Required regularly |
What's included
Cozy Heat 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 - each natural stone is unique in shape and an extra box allows selection of the best-fitting pieces.
Why the Cozy Heat Through-Wall Package stands out
Firebox from outside - clean sauna interior
Wood is loaded, fire is tended, and ash is removed from outside the sauna room. No wood chips, bark, or ash on the sauna floor. No smoke entering the room when the firebox door is opened. The sauna interior stays clean and undisturbed throughout the session - the most practical operational advantage of through-wall installation over any conventional floor-standing stove.
Bathers undisturbed during firing
Because the firebox door is on the exterior side of the wall, wood can be loaded and the fire managed while bathers are in session without anyone entering the sauna room. The session is not interrupted by fire-tending. This is especially valuable in a sauna used by multiple bathers where the comfort and privacy of the session should not be broken by operational maintenance.
The traditional Nordic installation method
Through-wall firebox loading is the oldest and most traditional installation method for wood-fired Nordic and Baltic saunas - the design that defined the Finnish smoke sauna and the Estonian heated chamber before modern stoves brought the firebox inside. For buyers who want not just the heat but the full traditional sauna operational experience, the Through-Wall is historically the most authentic choice.
Same Cozy Heat performance
5mm stainless flame cutter, three-stage combustion, 25-40% less firewood, 73.9% / 81.3% efficiency, EN 15821:2010 and German BlmSchV DIN EN 13240 Level 2 certification. Identical to every other Cozy Heat model in all performance and efficiency specifications. The installation type changes, the engineering does not.
12kW or 18kW with stones included
12kW for rooms 210-423 cu ft with minimum 265 lbs stones included. 18kW for rooms 317-635 cu ft with minimum 353 lbs stones included. Stone style selected at checkout. Each natural stone is unique in shape - an additional box allows selection of best-fitting pieces for the Through-Wall's stone cavity.
Requires qualified installation - plan before purchasing
The wall penetration must be correctly sized, fire-protected, and installed by a qualified professional. A chimney must also be installed separately. The sauna building must have an accessible adjacent space on the exterior side of the sauna wall. Confirm the building layout and engage a qualified installer before ordering the Through-Wall stove.
About Cozy Heat
Handmade in Estonia - traditional installation
Cozy Heat Through-Wall. The traditional Estonian installation - fire outside, heat inside, bathers undisturbed.
Cozy Heat is an Estonian sauna stove manufacturer. The Through-Wall is the model for sauna buildings designed in the traditional Nordic and Baltic manner - where the firebox is on the exterior side of the sauna wall and wood is loaded and fire is tended from outside the bathing chamber. The same 5mm stainless flame cutter, three-stage combustion, and German EN 15821:2010 certification as every Cozy model, in an installation that keeps the sauna interior clean, the session undisturbed, and the fire management simple. For the correct building layout, it is the most operationally elegant wood-fired sauna installation available.
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Complete package - Through-Wall stove and stones (style selected at checkout)
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Firebox from outside - clean interior, bathers undisturbed, no smoke inside
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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
Through-Wall vs conventional Cozy models
Cozy Through-Wall vs base Cozy, O, OG, SW, and Quattro
The base Cozy, Cozy O, Cozy OG, Cozy SW, and Cozy Quattro all install inside the sauna room with the firebox door facing the bathers - wood is loaded from inside the hot room during or before the session. The Cozy Through-Wall installs so the firebox passes through the sauna wall, with wood loaded from the adjacent exterior space. Both types share identical output levels, stone requirements, combustion efficiency, certifications, and warranty. The Through-Wall requires a sauna building with an accessible space on the exterior side of a sauna wall - a changing room, utility corridor, or outdoor area. If the sauna room does not have this layout, any of the five conventional Cozy models is the appropriate choice. If the building layout supports through-wall installation, the Through-Wall is the most operationally practical and traditionally authentic option.
A chimney of the correct specification must be installed separately. The wall penetration must be fire-protected and installed by a qualified professional. Use only dry, seasoned hardwood. Do not overfire. Sweep the chimney regularly.
Manuals and Documents
Warranty
2-year warranty
The Cozy Heat 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 installation 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.
