Cozy Heat O Thru-Wall – Wood-Burning Sauna Stove | 12 kW & 18 kW

Cozy Heat O Thru-Wall – Wood-Burning Sauna Stove | 12 kW & 18 kW

Estonian Craftsmanship | External Firebox Access | Traditional Wood-Fired Heat | Efficient Combustion | Rounded Steel Design | Free U.S. Shipping

Bring authentic European sauna tradition into your home with the Cozy Heat O Thru-Wall Wood-Burning Sauna Stove, a premium heater that combines traditional wood-fired warmth with thoughtful modern engineering.

Designed and manufactured in Estonia, the Cozy Heat O Thru-Wall features a distinctive rounded steel frame, an extended firebox for convenient external fueling, and an advanced combustion system engineered for efficient heat production.

Unlike conventional wood-burning sauna stoves that require tending the fire inside the sauna room, the through-wall design allows you to load firewood and manage ash from an adjacent space, keeping the sauna interior cleaner and more peaceful.

Available in 12 kW and 18 kW configurations, the Cozy Heat O Thru-Wall provides the foundation for a relaxing, traditional sauna experience in small, medium, or larger private sauna rooms.

Whether you're building a custom backyard retreat or upgrading an existing wood-fired sauna, Cozy Heat brings timeless craftsmanship, dependable heating, and thoughtful functionality together.

Why Choose the Cozy Heat O Thru-Wall?

Convenient Through-Wall Firebox Design

Enjoy the atmosphere of a wood-fired sauna without storing firewood or tending the fire inside the sauna room.

The Cozy Heat O Thru-Wall features an extended combustion chamber designed to pass through a properly constructed wall.

This allows firewood to be added and the firebox to be accessed from an adjacent area, creating a more comfortable and organized sauna environment.

The design is particularly appealing for custom sauna installations where a separate fire-tending area is preferred.

Authentic Traditional Sauna Warmth

Experience the inviting warmth of real wood-fired sauna bathing.

The Cozy Heat O Thru-Wall uses natural firewood to heat the sauna room and surrounding sauna stones, creating the gentle, enveloping warmth associated with traditional Nordic sauna culture.

Unlike infrared heating systems, this stove heats the surrounding sauna environment through a wood-burning fire and heat-retaining stones.

Create Traditional Sauna Steam

The Cozy Heat O Thru-Wall is designed to accommodate a substantial quantity of sauna stones.

As the stones absorb heat, they provide lasting warmth and allow you to customize the sauna's humidity.

Carefully pouring water over properly heated stones creates bursts of steam, adding a rich, traditional dimension to your sauna experience.

Advanced Three-Stage Combustion

Cozy Heat uses an engineered combustion system that directs air through multiple areas of the fire chamber.

This design helps burn combustible gases more completely, improving heat generation and supporting cleaner operation.

According to manufacturer-reported comparisons, Cozy Heat stoves can use approximately 25–40% less firewood than selected conventional heaters.

Actual fuel savings depend on firewood quality, chimney draft, installation, and operation.

Engineered for Cleaner Burning

The Cozy Heat O Thru-Wall is designed to meet stringent European combustion and emissions requirements.

Its advanced airflow system helps reduce unnecessary smoke and improve combustion efficiency.

The manufacturer identifies compliance with applicable German BImSchV emissions standards.

This combination of traditional wood heat and efficient combustion makes Cozy Heat a practical option for customers who appreciate both sauna performance and thoughtful engineering.

Premium Estonian Construction

Cozy Heat stoves are manufactured in Estonia, a country with a longstanding tradition of wood-fired sauna bathing.

The heater incorporates durable steel construction and a heavy-duty 5 mm stainless steel flame cutter engineered for repeated exposure to intense heat.

Its robust design is built for the demands of regular sauna use when installed and maintained according to manufacturer instructions.

Distinctive Rounded O-Series Design

The Cozy Heat O features a rounded outer frame that blends timeless sauna styling with contemporary craftsmanship.

The open stone-surround configuration provides generous space for heat-retaining sauna stones while creating an attractive focal point inside your sauna.

Its compact, floor-mounted design works well in appropriately sized custom sauna installations.

Available in Two Heating Capacities

Select the stove that best matches your sauna room.

Cozy Heat O Thru-Wall 12 kW

Designed for sauna rooms of approximately 210–423 cubic feet (6–12 m³).

An excellent option for smaller and medium-sized traditional wood-fired saunas.

Cozy Heat O Thru-Wall 18 kW

Designed for sauna rooms of approximately 317–635 cubic feet (9–18 m³).

Well suited to larger personal saunas and more spacious shared sauna environments.

Correct heater sizing depends on room volume, insulation, ceiling height, and the amount of glass or other uninsulated surfaces.

Ideal for Your Sauna & Wellness Space

Backyard Sauna Retreats

Create an authentic wood-fired sauna experience with the convenience of external firebox access.

Custom Sauna Construction

Integrate a premium Estonian sauna heater into a purpose-built traditional sauna room.

Post-Adventure Relaxation

Enjoy comforting warmth after skiing, hiking, cycling, or other outdoor activities.

Everyday Muscle Comfort

Sauna heat may temporarily ease ordinary muscle stiffness and support relaxation after demanding days.

Traditional Sauna Rituals

Experience the combination of firewood, heated stones, and adjustable steam that defines traditional sauna bathing.

Shared Wellness Experiences

Create a comfortable sauna environment for enjoying time with family and friends.

Key Features

• Through-Wall Firebox: Load firewood from an adjacent area.

• 12 kW & 18 kW Options: Heating capacity for different sauna sizes.

• Traditional Wood-Burning Heat: Authentic sauna warmth without electric heating elements.

• Made in Estonia: European sauna craftsmanship.

• Advanced Three-Stage Combustion: Engineered for efficient burning.

• Reduced Firewood Consumption: Manufacturer-reported efficiency improvements.

• Cleaner Combustion: Designed to meet applicable European emissions requirements.

• Rounded O-Series Steel Frame: Attractive, distinctive appearance.

• 5 mm Stainless Steel Flame Cutter: Durable high-temperature component.

• Generous Sauna Stone Capacity: Supports lasting warmth and traditional steam.

• External Fire Management: Helps keep routine wood handling outside the sauna.

• Floor-Mounted Installation: Designed for compatible custom sauna projects.

• Free U.S. Shipping: Available for eligible destinations.

Technical Specifications

Specification	O Thru-Wall 12	O Thru-Wall 18
Brand	Cozy Heat	Cozy Heat
Model	O-TW 12	O-TW 18
Product Type	Through-Wall Wood-Burning Sauna Stove	Through-Wall Wood-Burning Sauna Stove
Nominal Heating Capacity	12 kW	18 kW
Recommended Sauna Volume	210–423 cu. ft.	317–635 cu. ft.
Recommended Sauna Volume (Metric)	6–12 m³	9–18 m³
Fuel	Seasoned Firewood	Seasoned Firewood
Maximum Log Length	13" / 33 cm	15.7" / 40 cm
Required Chimney Draft	12 Pa	12 Pa
Manufacturer-Listed Thermal Efficiency	73.9%	81.3%
Recommended Stone Load	100–120 kg	140–160 kg
Recommended Sauna Stone Size	7.5–15 cm	7.5–15 cm
Flue Connection	Top	Top
Combustion Chamber	Extended Through-Wall	Extended Through-Wall
Main Construction	Steel	Steel
Flame Cutter	5 mm Stainless Steel	5 mm Stainless Steel
Mounting	Floor-Mounted	Floor-Mounted
Country of Manufacture	Estonia	Estonia
Supplier Reference	SAK93612	SAK93612

What's Included

• Cozy Heat O Thru-Wall Wood-Burning Sauna Stove in Selected Size

• Rounded Outer Heater Frame

• Wood-Burning Heater Body

• Extended Through-Wall Combustion Chamber

• Firebox Door with Glass

• Ash Collection Components

• Manufacturer-Supplied Stove Components

• Installation & Operating Manual

A compatible chimney system, fire-protection materials, and other installation accessories are selected separately according to the sauna design.

Installation & Setup

The Cozy Heat O Thru-Wall is a wood-burning appliance that requires careful planning and correct installation.

1. Choose the Appropriate Model: Select the 12 kW or 18 kW version according to the sauna's heated volume and construction.

2. Plan the Wall Opening: Use the manufacturer's specifications for the through-wall combustion chamber, noncombustible construction, and required clearances.

3. Prepare the Stove Foundation: Position the appliance on a stable, properly protected, heat-resistant surface.

4. Install a Compatible Chimney: Use an appropriately sized chimney and flue system that safely vents combustion gases.

5. Provide Adequate Ventilation: Follow the manufacturer's combustion-air and sauna ventilation requirements.

6. Complete the Initial Firing: Follow the manufacturer's first-heating procedure to cure the stove's protective coating.

7. Install Sauna Stones: Use approved sauna stones and arrange them according to the installation manual.

8. Operate & Maintain: Burn properly seasoned firewood and follow the manufacturer's firing, cleaning, and maintenance procedures.

Professional installation is strongly recommended. Wood-burning through-wall heaters require proper chimney design, fire-resistant construction, ventilation, and compliance with applicable building and fire codes.

Shipping & Delivery

FREE U.S. SHIPPING

Enjoy complimentary shipping on the Cozy Heat O Thru-Wall Sauna Stove to eligible U.S. destinations.

• Order Processing: Typically packed and shipped within 1–3 business days.

• Estimated Delivery: Approximately 5–10 business days.

• Available Models: 12 kW and 18 kW.

• Delivery Method: Appropriate parcel or freight shipment depending on the selected model and shipment configuration.

Delivery times are supplier-advertised estimates and may vary based on product availability, destination, and carrier scheduling.

Frequently Asked Questions

What makes the Cozy Heat O Thru-Wall different from a standard wood-burning sauna stove?

The through-wall design allows firewood to be added from an adjacent area, helping keep wood storage, ash handling, and routine fire tending separate from the sauna interior.

What is the difference between the 12 kW and 18 kW models?

The 12 kW version is designed for sauna rooms of approximately 210–423 cubic feet, while the 18 kW version is intended for rooms of approximately 317–635 cubic feet.

The appropriate choice depends on insulation, ceiling height, and uninsulated surfaces.

Does the stove require electricity?

No electrical heating connection is required. The Cozy Heat O Thru-Wall generates heat by burning firewood.

Can I pour water over the stones?

Yes. With approved sauna stones properly installed and heated, the stove supports traditional steam-producing sauna bathing. Apply water according to manufacturer instructions.

Does the stove need a chimney?

Yes. A properly installed chimney system is essential for safe operation and combustion-gas venting.

Can I install the stove in an existing sauna?

Potentially, provided the sauna meets the stove's requirements for space, wall penetration, chimney installation, ventilation, floor protection, and safety clearances.

What type of firewood should I use?

Use dry, seasoned firewood of the size recommended for your selected model. Do not burn treated, painted, or contaminated wood.

How does the Cozy Heat O Thru-Wall improve combustion efficiency?

Its engineered combustion chamber distributes combustion air through multiple stages, helping burn flue gases more completely and generate heat efficiently.

Is the Cozy Heat O Thru-Wall suitable for backyard saunas?

Yes. It is suitable for properly designed traditional sauna installations with compliant chimney systems, fire protection, and ventilation.

Traditional Sauna Warmth with Added Convenience

The Cozy Heat O Thru-Wall Wood-Burning Sauna Stove brings together authentic Estonian craftsmanship, efficient combustion, and thoughtful external firebox access.

Its rounded steel design, generous stone capacity, and wood-fired heating create a welcoming traditional sauna environment, while the through-wall construction helps keep your bathing space cleaner and more peaceful.

Available in 12 kW and 18 kW configurations, the Cozy Heat O Thru-Wall is a distinctive choice for custom backyard sauna retreats and traditional home wellness spaces.

Authentic fire. Lasting warmth. Estonian sauna craftsmanship.

Important Safety Information

This wood-burning sauna stove must be installed and operated according to manufacturer instructions and applicable building and fire codes.

Proper chimney venting, combustion ventilation, floor protection, noncombustible wall construction, and required clearances are essential for safe operation.

Never operate the stove without an appropriate chimney system. Install smoke and carbon monoxide alarms as required by applicable codes.

Use only manufacturer-approved sauna stones and appropriately seasoned firewood. Follow all instructions for initial firing, maintenance, and applying water to heated stones.

Never leave an operating wood-burning stove unattended.

Sauna bathing involves high temperatures and may not be suitable for everyone. Individuals with cardiovascular conditions, uncontrolled blood pressure, impaired heat sensitivity, or other relevant medical concerns should seek qualified medical guidance before sauna use.