Wood Sauna Heater - The Ultimate Choice?

Wood Sauna Heater - Harvia M3 Woodburning Stove

The wood sauna heater is where the great Finnish sauna bathing tradition began and it is still the top choice of sauna purists today. Many people believe that nothing can compare to the crackling of the fire, the pungent smell of the smoke and the ambiance of the flames.

From a practical standpoint, a wood sauna heater is a great alternative to an electric or gas heater since it doesn’t require a connection to your home’s utilities. That makes it the ideal option for an outdoor sauna as you have the freedom to locate your sauna anywhere you wish. Of course, a propane heater also gives you some flexibility but it lacks the aesthetic beauty of a traditional wood fire.

A wood sauna heater works much the same as a regular fireplace. You use wood to build a fire and produce heat, then pour water over the stones which are set on a tray at the top of the stove to create steam. The effectiveness of the heater and the benefits of the sauna experience will rely heavily on the type of wood you use to build your fire.

Softwoods like pine, cedar and fir can be used to start a fire but should not be used as the main wood for burning since they will burn quickly.  Hardwoods like oak, birch, maple, ash and poplar are recommended for use in your wood sauna heater as they will burn longer, providing you a better overall sauna experience.

How Do You Install a Wood Sauna Heater?

Wood Sauna Heater - Harvia Model

Because a wood sauna heater is similar to a wood-burning fireplace, installation must be done carefully. You’ll need to know the local building code as well as manufacturer specs to ensure the proper clearance from combustibles in the sauna room. Before you begin installation, check all regulations.

For insurance reasons, wood burning stoves must be installed in detached sauna buildings and are usually not acceptable in the main residence. However, they are ideal for outdoor sauna cabins with no electricity since they don’t have to be connected to your home’s electrical system.

Since a wood sauna heater installation can be a complicated process with its own special concerns for stovepipe and chimney connections, it’s usually a good idea to hire a professional to do the work.

Here are a few tips for installing a wood burning sauna stove:

  • The floor or base the sauna stove sits on should be a minimum of 2” of concrete, or 1/4” thick fiber-reinforced concrete plate covered by a metal plate.
  • In addition, the floor in front of the stove must be protected using acceptable material (such as a metal plate) that extends 12” beyond the width of the oven mouth and 18” in front of it.
  • The wood sauna heater should not be closer than 12” from any wall. If it is closer, the wall must be covered with a flame-resistant shield.
  • A wood burning stove must be connected either to a sound masonry chimney or a UL approved Stainless Steel Class "A" Insulated Chimney.
  • Check the heater instructions regarding requirements for the stovepipe that connects the sauna stove to the chimney. They usually require it to be something like 7” in diameter and must be made of double-walled steel.
  • A sauna room with a wood burning sauna stove needs an external air intake vent. Since wood heaters can be difficult to regulate and can get very hot, you’ll need a vent with an adjustable cover to allow more air to circulate into the room. As for an exhaust vent, the flue does that job.
  • Always consider all safety requirements for wood burning appliances to avoid any issues.

Firing up the Wood Sauna Heater

Most sauna stoves will accommodate logs up to about 16” in length. The wood should be cut at least a year in advance, be properly dried, and then stored out of the weather (that is, cover it with plastic if it’s to remain outdoors).

Never use painted or stained wood, or wood from trees that contain sap, as these can emit toxic fumes when burned. Also, avoid using green wood, or wood that has been freshly cut, as it contains too much moisture. The ideal logs for burning should have a moisture content of 20% or less.

In general, the best wood for using in your sauna heater should be smooth and uniform in color with no broken knots. This will allow it to withstand drastic changes of temperature and provide a sustained, even heat.

Aside from the wood, another important feature to consider when choosing a wood heater is whether it feeds from inside or outside the sauna. Some people prefer an outside feeding heater to free up space and prevent the need for cleanup inside but bear in mind that you will lose about 25% of the heat inside the sauna with an outdoor feed. 

Feeding from the inside gives you the homey experience of a traditional fireplace and that can be further enhanced if you buy a wood burning sauna stove with a glass window. This can add to the ambiance of your sauna as you experience the look of the warming flames. 

Some models of wood heaters also include an attached water heater, which is an added advantage if you are in a remote area where there is no electricity available to heat your water.

Best Wood Burning Sauna Stoves

There are a number of wood burning sauna heaters on the market, but here are three of the best options we’ve found.

1.   Harvia 20SL Woodburning Sauna Heater

Designed for those who want to heat their sauna from another room or outside the building, the Harvia 20SL has an adaptable door that can be converted for either indoor or outdoor feed. It can also be connected to a separate water tank.

It has adjustable legs which make it easy to install evenly in rooms with an inclined floor. Like the M3 model, it also features a glass door to allow sauna users to enjoy fire-gazing. It measures 17” x 28 ¾” x 30” and is ideal for heating larger rooms from 282 to 706 cubic feet. Retails for $1,875.

2.   Harvia Legend 240SL Woodburning Sauna Heater

With its unique galvanized black metal grate design, the Harvia Legend provides the ultimate sauna experience. Its matte black frame holds up to 450 lbs. of stones which not only create an aesthetically pleasing look but also helps to retain heat even as the fire dies down, allowing for a longer sauna bath. 

The fire chamber of the Legend model has a modern grate structure that works to separate the combustion air, directing part of it to the upper part of the fire chamber for cleaner and more efficient burning. With a smaller safety distance between the back and sides of the stove and the burning wood, you have more flexibility in the placement of the benches and the grate structure gives the stove a longer lifespan. 

The door adjusts for indoor or outdoor feed and it can be equipped with a pipe-mounted water heater. It has adjustable legs for easy installation on uneven floors. It measures 23 5/8” x 23 5/8” + 7 1/8” collar x 32 ¾” and can heat rooms from 353 to 848 cubic feet. Retails for $2,500.

3.   Huum HIVE Wood

This sleek, modern heater comes from Huum, an Estonia based company, and is designed to maximize the good negative ions from the stones by using the minimal amount of metal. The round stainless steel cage encloses 198 pounds of stones.

There is a firebox extension available which allows you to heat the sauna from another room. It is on the higher end cost wise, retailing at $3,100, but it does come with a 5 year guarantee. The stones and chimney connection must be purchased separately. It measures 17 ¾” x 18 1/8” x 18 1/8” and is designed specifically for smaller rooms, with a capacity of 210 to 460 cubic feet.

Wood Sauna Heaters - Bottom Line

A sauna stove that burns wood offers soft löyly, soft heat, and the pleasurable experience of a crackling wood fire. Studies show it can also provide a number of health benefits from easing painful joints to improving cardiac health and even lowering the risk of dementia and Alzheimer's.

Most sauna enthusiasts will tell you that any other type of sauna heater - electric, gas, or infrared - just won’t compare to the real thing.

So if you want the most authentic sauna experience with all of the comforts of sitting in front of a fireplace than a wood burning sauna heater is the choice for you.

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