Cozy Heat Thru-Wall Sauna Heater
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The Cozy Heat TW Wood-Burning Sauna Stove is a through-the-wall, wood-fired sauna heater that lets you load firewood from outside your sauna for a cleaner, more relaxing space. Hand crafted in Estonia, where sauna bathing is a way of life, the Cozy TW delivers mild, long-lasting heat over a deep stone mass and is designed for generous löyly when you pour water over the hot sauna rocks.
Key Features
- Through-the-wall wood-burning sauna stove for loading firewood from outside the sauna room
- Perfect for intimate home and cabin saunas that want traditional heat with a tidy interior
- High-efficiency combustion that uses approximately 25 to 40 percent less wood than many comparable stoves
- Clean-burning design with smoke gases up to 6 times cleaner than standard wood stoves (German BIMSCH certified)
- Large stone capacity for deep thermal storage and soft, long-lasting steam
- Durable steel construction with black finish for a modern, understated look
- Floor-mounted thru-wall installation that saves floor space in the sauna and keeps wood handling outside
- Designed and engineered in Estonia by a specialist wood-fired sauna stove manufacturer
Required Components
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Sauna Stones:
- Cozy TW 12 kW: Minimum 265 lbs of sauna stones
- Cozy TW 18 kW: Minimum 353 lbs of sauna stones
- Chimney System: A compatible, code compliant wood-burning sauna chimney and flue kit is required for safe installation.
What’s Included
- Cozy Heat TW thru-wall wood-burning sauna stove (12 kW or 18 kW model)
- Outer heater frame and thru-wall sleeve
- Chimney connection outlet on top of the heater
- Heater body with integrated stone basket
- Firebox and door for loading from outside the sauna
- Ash box and cleaning access
- Installation and Operation Manual
- 2-year manufacturer warranty (residential use)
Specifications: Cozy TW 12 kW
| Model | Cozy TW 12 |
| Heater Type | Wood-burning sauna stove, thru-wall, floor mounted |
| Power Output | 12 kW |
| Sauna Room Size | 210 to 423 cu ft (approximately 6 to 12 m³) |
| Stone Requirement | Minimum 265 lbs of sauna stones (10 to 15 cm) |
| Installation Type | Floor mount, thru-wall firebox feed from outside sauna room |
| Minimum Opening Width (Wall) | 255 mm (approximately 10.03 in) |
| Minimum Height From Floor to Opening | 440 mm (approximately 17.32 in) |
| Maximum Wall Thickness | 150 mm (approximately 5.9 in) |
| Flue Connection Location | Top of heater to chimney system |
| Safety Distance From Wall Opening to Combustibles | Sides of opening: 500 mm (about 19.68 in); above opening: 960 mm (about 37.8 in) |
| Primary Fuel | Wood logs only |
| Color / Finish | Black steel |
| Certifications | German BIMSCH certificate, high efficiency and low emissions |
| Country of Origin | Estonia |
Specifications: Cozy TW 18 kW
| Model | Cozy TW 18 |
| Heater Type | Wood-burning sauna stove, thru-wall, floor mounted |
| Power Output | 18 kW |
| Sauna Room Size | 317 to 635 cu ft (approximately 9 to 18 m³) |
| Stone Requirement | Minimum 353 lbs of sauna stones (10 to 15 cm) |
| Installation Type | Floor mount, thru-wall firebox feed from outside sauna room |
| Minimum Opening Width (Wall) | 315 mm (approximately 12.40 in) |
| Minimum Height From Floor to Opening | 470 mm (approximately 18.50 in) |
| Maximum Wall Thickness | 150 mm (approximately 5.9 in) |
| Flue Connection Location | Top of heater to chimney system |
| Safety Distance From Wall Opening to Combustibles | Sides of opening: 500 mm (about 19.68 in); above opening: 960 mm (about 37.8 in) |
| Primary Fuel | Wood logs only |
| Color / Finish | Black steel |
| Certifications | German BIMSCH certificate, high efficiency and low emissions |
| Country of Origin | Estonia |
Why Choose the Cozy Heat TW?
- Authentic wood-fired sauna experience with gentle, long-lasting heat and rich steam
- Thru-wall firebox design keeps wood, ash, and mess outside the sauna room for a cleaner interior
- Efficient, eco conscious combustion that reduces wood consumption and emissions compared to typical wood stoves
- Large stone mass that stores heat and delivers smooth, consistent löyly for longer sessions
- Compact footprint that works well in smaller or more intimate sauna spaces
Shipping & Returns
- Ships: Typically within 3 to 7 business days (freight delivery with scheduled appointment)
- Delivery: Free standard U.S. shipping to most locations
- Returns: 14 day return policy on unused, uninstalled stoves in original packaging
Installation and Operation Manual
Frequently Asked Questions
What is the difference between the Cozy TW 12 kW and 18 kW models?
The Cozy TW 12 is designed for sauna rooms from about 210 to 423 cubic feet and uses at least 265 pounds of stones. The Cozy TW 18 is sized for larger rooms from about 317 to 635 cubic feet and requires at least 353 pounds of stones. If your sauna is larger, has more glass or tile, or is in a colder climate, the 18 kW model is usually the better choice.
How does a thru-wall sauna stove work?
A thru-wall sauna stove is installed in a masonry or brick wall between your sauna room and an adjacent space. You load firewood from outside the sauna, and the heater body and stones sit in the sauna room. This keeps the interior cleaner and makes it easier to tend the fire without opening the sauna door as often.
What kind of wall opening do I need for the Cozy TW?
The stove is installed in an opening in a concrete or brick wall. For the 12 kW model, the minimum opening width is about 255 mm and the minimum height from the floor is about 440 mm. For the 18 kW model, the minimum opening width is about 315 mm and the minimum height from the floor is about 470 mm. The maximum wall thickness is 150 mm. Always follow the manufacturer instructions and local code.
How many stones do I need and what type is best?
The Cozy TW 12 requires at least 265 pounds of sauna stones. The Cozy TW 18 requires at least 353 pounds. Use natural sauna stones such as olivine or peridotite in the recommended size range. Avoid river rocks or decorative stones, since they can crack or shatter under high heat. Many installers buy an extra box of stones so they can choose ideal shapes for airflow and fit.
How long does it take to heat the sauna?
Most saunas reach bathing temperature in about 45 to 75 minutes depending on room size, insulation, stone loading, and wood quality. The 18 kW model usually heats larger rooms more quickly due to its higher output and larger firebox.
Does the Cozy TW require a chimney?
Yes. A certified wood-burning chimney system is required. Use metal flue pipe and chimney components that are rated for wood-burning sauna stoves and that comply with local building and fire codes. Professional installation is strongly recommended for safety and performance.
Do I need professional installation?
Professional installation is highly recommended. A qualified installer will cut and finish the wall opening, configure the chimney system, verify clearances to combustibles, and make sure the stove meets local building and fire safety requirements for wood-burning appliances.
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