The Harvia 20 SL is a wood-burning sauna stove built for saunas where the firebox is loaded from an adjacent room or from outside the building. Its through-wall design keeps wood, ash, and smoke management outside the sauna space, while the glass door brings warmth and visual character to the interior. Adjustable legs simplify installation on uneven floors, and a 6-inch pipe adapter is included to connect to standard chimney pipe. For small to medium-sized saunas where a traditional wood-fired experience is the priority, the 20 SL is a practical and well-built option.
Why Customers Choose the Harvia 20 SL
- Through-wall firing design keeps wood loading and ash management outside the sauna room
- Glass door provides a view of the fire from inside the sauna
- Adjustable legs allow level installation on sloped or uneven floors
- 6-inch pipe adapter included — converts metric pipe to standard US chimney pipe size
- Covers sauna rooms from 282 to 706 cubic feet
- UL Listed for safety compliance
- Door opening direction can be reversed for flexible installation
- Manufactured by Harvia, a Finnish sauna equipment manufacturer with decades of production history
Product Highlights
Through-Wall Firing Design
The 20 SL is engineered to be loaded from outside the sauna room — through a wall, from an adjacent space, or from outside the building. This keeps the sauna interior clean and free of wood debris and ash during and after use.
Glass Door
All Harvia SL series stoves include a glass door, allowing the fire to be visible from inside the sauna. The glass door adds to the atmosphere of the session while maintaining a sealed firebox.
Reversible Door Opening
The door hinge can be configured to open from either side, giving installers flexibility to accommodate the wall opening direction and room layout without modification.
Adjustable Legs
The 20-series adjustable leg system allows the stove to be leveled during installation even when the floor surface is not perfectly flat — a practical feature for outdoor sauna buildings and older structures.
Standard 6-Inch Pipe Adapter Included
The stove ships with an adapter that converts the metric flue outlet to a standard 6-inch US chimney pipe size, simplifying connection to locally sourced chimney components.
UL Listed
The Harvia 20 SL is UL Listed, confirming it has been independently tested and meets applicable safety standards for use in the United States and Canada.
Specifications
| Model | Harvia 20 SL |
| SKU | WKPR20SLM |
| Fuel Type | Wood-burning |
| Firing Position | Through-wall (loaded from outside the sauna room) |
| Room Coverage (Min) | 282 cu ft |
| Room Coverage (Max) | 706 cu ft |
| Width | 20 in (508 mm) |
| Depth | 17 in (432 mm) |
| Height | 30 in (762 mm) |
| Door | Glass door (reversible opening direction) |
| Legs | Adjustable (for level installation on uneven floors) |
| Flue Outlet | 6-inch (adapter included to convert from metric) |
| Safety Certification | UL Listed |
| Country of Manufacture | Finland |
| Shipping Weight | 300 lbs |
What's in the Box
- Harvia 20 SL wood-burning sauna stove
- 6-inch chimney pipe adapter (metric-to-standard conversion)
- Adjustable legs
- Installation and operation manual
Ideal For
- Small to medium-sized saunas between 282 and 706 cubic feet
- Sauna buildings where wood loading from outside or an adjacent room is preferred
- Outdoor sauna cabins and detached sauna structures
- Homeowners who prefer a traditional wood-fired sauna experience
- Installations where keeping the sauna interior free of wood and ash is a priority
Important Information
- Professional installation required. Wood-burning sauna stoves must be installed by a qualified professional in accordance with all applicable local building codes, fire codes, and clearance requirements. Improper installation creates a fire hazard.
- Chimney system not included. A compatible chimney system must be sourced and installed separately. The included adapter converts the metric flue outlet to a standard 6-inch US pipe size. Consult a chimney professional to specify the correct system for your installation.
- Clearance requirements. Maintain all minimum clearances from combustible materials as specified in the installation manual. Do not reduce clearances without written authorization from the manufacturer.
- Sauna stones not included. Sauna stones are required for proper operation and must be purchased separately. Use only stones rated for sauna use.
- Through-wall installation. The 20 SL is designed for through-wall firing. The wall penetration must be constructed in accordance with the installation manual and applicable fire codes. Do not use this stove as a freestanding unit without the appropriate wall installation.
- Not for indoor residential heating. This stove is designed for sauna use only. Do not use it as a general-purpose wood stove or space heater.
- Ventilation. Adequate combustion air supply and exhaust ventilation must be provided as specified in the installation manual.
Frequently Asked Questions
What does "through-wall" firing mean?
Through-wall firing means the firebox door and loading area are positioned on the exterior side of the sauna wall, so wood is added and ash is removed from outside the sauna room. The heat radiates through the stove body into the sauna interior, keeping the sauna space clean during use.
What size sauna room is the 20 SL designed for?
The Harvia 20 SL is rated for sauna rooms between 282 and 706 cubic feet. Room size calculations should account for wall insulation, glass area, and ceiling height. Consult your installer or a sauna heater sizing guide to confirm the 20 SL is appropriate for your specific room.
Is a chimney system included?
No. The chimney system must be purchased and installed separately. The stove includes an adapter that converts the metric flue outlet to a standard 6-inch US chimney pipe size. A chimney professional should specify the correct system for your installation and local code requirements.
Are sauna stones included?
No. Sauna stones are not included and must be purchased separately. Use only stones rated for sauna use — do not substitute with other rock types, as this can damage the stove and create a safety hazard.
Can the door opening direction be changed?
Yes. The door hinge on the 20 SL can be reversed to open from either side, providing flexibility to accommodate different wall opening configurations and room layouts.
Is the 20 SL UL Listed?
Yes. The Harvia 20 SL is UL Listed, confirming it has been independently tested and meets applicable safety standards for use in the United States and Canada.
Can the 20 SL be connected to a water tank?
The standard 20 SL model is not a boiler stove. Harvia does offer boiler variants in the 20-series that can be connected to a separate water tank. Contact your dealer to confirm which model is appropriate if a boiler connection is required.
What are the floor clearance requirements?
Minimum clearances from combustible materials are specified in the installation manual included with the stove. All clearance requirements must be followed as written. Do not reduce clearances without manufacturer authorization. Consult a qualified installer if you have questions about your specific installation.
The Harvia 20 SL is a well-built, UL Listed wood-burning stove for sauna owners who want a traditional fire-heated experience with the practical advantage of outside-room loading. If the specifications match your room size and installation setup, it is a reliable choice backed by Harvia's established manufacturing standards. Review the Important Information section and consult a qualified installer before ordering to confirm the 20 SL is the right fit for your project.