Cozy Heat O Thru-Wall Sauna Stove
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The Cozy Heat O TW Thru-Wall Wood-Burning Sauna Stove combines traditional wood-fired sauna heat with a clean, elegant through-the-wall design. Hand crafted in Estonia, where sauna bathing is a way of life, the Cozy O TW lets you load firewood from outside the sauna for a tidy interior space. Its circular rim body, high stone mass, and efficient combustion deliver mild, long-lasting heat and rich, luxurious steam when you pour water over the hot sauna stones.
Key Features
- Through-the-wall wood-burning sauna stove for loading firewood from outside the sauna room
- Innovative circular rim design that enhances both aesthetics and even heat distribution throughout the sauna
- High-efficiency combustion uses approximately 25 to 40 percent less wood than many comparable sauna stoves
- Clean-burning performance with very low emissions and high efficiency
- Large stone capacity for deep heat storage and soft, long-lasting löyly
- Durable steel construction with a modern black finish
- Floor-mounted thru-wall installation that keeps wood, ash, and mess outside the sauna room
- Designed and engineered in Estonia by a specialist wood-fired sauna stove manufacturer
Required Components
- Sauna Stones:
- Cozy O TW 12 kW: Minimum 265 lbs of sauna stones
- Cozy O TW 18 kW: Minimum 353 lbs of sauna stonesUse natural, angular sauna stones such as olivine or peridotite in the 10 to 15 cm range. Avoid river rocks or decorative stones. Many installers recommend ordering an extra box so you can hand select stone shapes for the best airflow, fit, and steam quality.
- Chimney System: A compatible, code compliant wood-burning sauna chimney and flue kit is required for safe installation.
What’s Included
- Cozy Heat O TW thru-wall wood-burning sauna stove (12 kW or 18 kW model)
- Outer frame of the heater 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 O TW 12 kW
Model
Cozy O 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)
Dimensions (D × W × H)
24.08 in × 19.88 in × 29.76 in
Heater Weight (Without Stones)
Approximately 108 lbs
Room Size Heating Capacity
Up to 423 cu ft (depending on insulation and materials)
Installation Type
Floor mount, thru-wall firebox loaded from outside sauna room
Flue Connection Location
Top of heater to chimney system
Primary Fuel
Wood logs only
Material / Finish
Steel construction with black finish
Certifications
High efficiency and low emissions, meets strict European standards
Country of Origin
Estonia
Specifications: Cozy O TW 18 kW
Model
Cozy O 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)
Dimensions (D × W × H)
24.58 in × 19.68 in × 29.76 in
Heater Weight (Without Stones)
Approximately 154 lbs
Room Size Heating Capacity
Up to 635 cu ft (depending on insulation and materials)
Installation Type
Floor mount, thru-wall firebox loaded from outside sauna room
Flue Connection Location
Top of heater to chimney system
Primary Fuel
Wood logs only
Material / Finish
Steel construction with black finish
Certifications
High efficiency and low emissions, meets strict European standards
Country of Origin
Estonia
Why Choose the Cozy Heat O TW?
- Authentic wood-fired sauna experience with mild, long-lasting heat and naturally rich steam
- Thru-wall firebox design keeps wood, ash, and mess outside the sauna room for a cleaner interior
- Efficient and eco conscious combustion that reduces wood consumption and emissions compared to many standard wood stoves
- Large stone mass that stores heat and delivers smooth, consistent löyly even during longer sessions
- Distinctive circular rim look that adds a modern, sculptural focal point to your sauna design
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
Pro Tip: When stacking stones, place larger pieces at the bottom of the basket and medium stones toward the top so air can move freely between them. This helps the Cozy O TW heat faster, protects the firebox, and creates softer, more consistent steam. Inspect stones regularly and replace any that are cracked or flaking.
Installation and Operation Manual
Frequently Asked Questions
What is the difference between the Cozy O TW 12 kW and 18 kW models?
The Cozy O TW 12 is sized for sauna rooms from approximately 210 to 423 cubic feet and uses at least 265 pounds of stones. The Cozy O TW 18 is designed for larger rooms from about 317 to 635 cubic feet and uses 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 solid wall between your sauna room and an adjacent space. You load firewood from outside the sauna, while the heater body and stones sit in the sauna interior. This keeps the sauna cleaner and makes it easier to tend the fire without opening the sauna door as often.
What kind of stones should I use and how many do I need?
Use natural sauna stones such as olivine or peridotite in the 10 to 15 cm range. The Cozy O TW 12 requires at least 265 pounds of stones and the Cozy O TW 18 requires at least 353 pounds. Many installers order an extra box of stones so they can choose ideal shapes for airflow and fit inside the stone basket.
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 typically heats larger rooms more quickly because of its higher output and larger firebox.
Does the Cozy O TW require a chimney?
Yes. A certified wood-burning chimney system is required. Use 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 create 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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