Sauna design, part 3/9: Choosing a stove

2020Finnish people have always been sauna people. There are more than 2 million saunas in Finland and every sauna needs a stove. In the last five years, pillar stoves have been the most popular stove. Especially in Sun Sauna’s tenders, the pillar heater is already the customer’s choice in about 70% of cases. The share of wood stoves has also been increasing slightly. This is due to the increase in the construction of outdoor saunas and the fact that new beautiful designer wood stoves with impressive glass doors have appeared on the market.

1.0 Stove design and materials

Stoves are available in a variety of designs and outer casing materials, here are a few examples.

• Currently, the most popular stoves are the so-called pillar stoves or tower stoves. Many manufacturers have their own range of pillar stoves. IKI-Kiuas Oy was the first to introduce a pillar stove. Most of the stoves are round, but there are also square, semicircular wall-mounted and corner-mounted stoves. The stoves use 100-200 kg of stones, which give a soft glow.
• Cast stone stoves, Tulikivi manufactures stoves with cast outer shells. The casting process produces beautiful stoves with an outer shell that does not get too hot, making them safe to use even in small sauna rooms.
• There are only a few manufacturers of “ready-to-use” stoves on the market. The ready-made ones were very popular 5-10 years ago, this type of stove is suitable for a sauna where you take a sauna every day. They are available in round and oval shapes. The most popular heater types are Harvia Forte and Helon Rondo.
• Cave stone pits are available from a few manufacturers, Mondex and Tulikivi.
• Basic wall-mounted heaters are usually at the lower end of the range. Stoves with a small mass of stone heat up quickly, but often have a slightly sharper flame than stoves with a larger mass of stone. Wall-mounted stoves are available from a number of stove manufacturers.
• In wood stoves, pillar stoves are also popular. IKI, for example, has around ten round stove models. Wood stoves can be found in the ranges of almost every stove manufacturer. Examples of old stove manufacturers are Narvi, which has been producing stoves since 1937, and Veto, which started producing stoves in 1949.
• There are also stoves on the market with both electric and wood stove features.

Sauna stoves: IKI Pilarikiuas, IKI Monolith, Magnum Original Malja, Mondex Rock, Tulikivi Naava, Mondex Nature.

All stoves go directly with Sun Sauna’s spa models, but it’s worth asking us for our opinion. For example, the IKI Monolith is a rectangular heater, so it fits very well with our Relax sauna.

2.0 Heater power selection

All heater manufacturers indicate the size of the sauna room for the heater in question, i.e. the minimum and maximum volumes of the room. For each heater model, several power ratings are available. The smallest stoves are 4.5 kW and the largest up to 30 kW. The most common stove models suitable for domestic saunas range from 6 to 9 kW.

If the sauna is completely panelled, the choice of stove is straightforward. Calculate the volume of the sauna and choose the right heater. A good rule of thumb is to choose a heater that is one degree more efficient if the volume of the sauna is close to the upper limit of the chosen model.

For example, my sauna has a volume of 12 m³, is a 7.5 kW heater enough or should I get a more powerful one?

• A stove is usually purchased for 10-15 years
• 7.5 kW is cheaper and has enough power to heat a sauna, but the heating time may be longer than normal.
• 9.0 kW is slightly more expensive, but the heating time is certainly shorter.

2.1 Effect of glass or stone surface on the choice of heater output

Glass and stone surfaces in the walls increase the power demand of the stove. Use this formula to ensure that the heater is powerful enough: every square metre of uninsulated (glass or stone) surface adds one cubic metre to the actual volume of the sauna! With a full-height glass sauna wall, the formula gives a slightly over-efficient stove. Check the power requirement of the stove with a sauna expert.

For example, the size of the sauna is 2,5m*2,0m and the height is 2,3m. The sauna has a glass wall and tiles on the door wall, covering the entire wall area. .

• The actual cubic volume of the sauna is: 2,5m x 2,0m x 2,3m = 11,5 m³
• The area of the front wall is: 2,5m x 2,3m = 5,75 m², this is directly converted into cubes.
• The calculated volume of the sauna, taking into account the uninsulated surfaces, is: 11,5m³ + 5,75m³ = 17,25 m³
• Without a glass wall, a 7.5-8.0 kW heater would be sufficient, but with a glass wall, the heater should have at least 10.0-10.5 kW of power.

3.0 Place of the stove in the sauna.

Before choosing the location of the heater in the sauna room, you must first place the door in the right place. The heater must be placed in the right position in relation to the position of the door for safety reasons. Most accidents in saunas occur with a stove. Therefore, compromises should be avoided between the position of the stove and the position of the door. Secondly, the heater should be positioned so that it is easy to use and easy to throw the stove.

Here are some examples of door and stove locations:

• Figure 1: When the sauna is narrow, less than 1900 mm wide, the door should always be placed to the side. There are only two safe locations for the heater. These are the corners of the front wall and the back wall. If the door were placed in the middle of the door wall, there would be so little space on either side that the stove would be very close to the doorway. Also, the other side wall would not fit a board properly in this case.
• Figures 2 and 3: When the width of the sauna increases slightly, e.g. to 2200 mm, the door can be placed either on the side or in the middle of the door wall. Again, in both cases, there are two safe places for the heater. In the figure, the dangerous heater locations for a sauna of this size are marked with a red cross.
• Figure 2: The safest stove locations are still in corners. If the stove is placed right next to the door, safety is reduced. Especially with an L-shaped seat, where the seat is located on the back wall of the sauna and on one side of the stove.
• Figure 3: Safe heater locations are in the corners of the door wall. For example, using an 800 mm wide door leaves 700 mm of space for the stove. The very popular counter-sitting laude is not safe for a sauna of this size. If a heater is placed in the middle of the back wall of a 2200 mm wide sauna room, the space between the heater and the seating area is only 380 mm (at these dimensions), i.e. the heater is too close to the sauna occupants.

• Figure 4: The sauna is spacious enough to increase the number of safe places to three. The most common locations are the corners of the door and the rear wall. A heater can also be considered in the middle of the front wall, especially if it can be protected by a railing. There is a safe distance between both the door and the seat (with the L-shaped table solution).
• Figure 5: The door is in the middle of the front wall. Now you can also place the stove in the middle of the back wall. With a rear wall width of 2600 mm, the distance between the stove and the seat is 580 mm, which is already a safe distance. Both corners of the door wall are also good places for the stove in this model. In this case, the seat is either L-shaped or U-shaped.

4.0 Integrating the heater into the foot bath

Tower chimneys can also be integrated or “embedded” through the footprint. Pillar/tower stoves generally have small fire protection distances. Often, when a heater is embedded through a footprint, an RST or glass collar is installed around the heater’s embedment opening. The collar sort of “lies” on top of the skirting. Each stove has its own collar, which can be ordered with the stove. The collar finishes off the heater’s surroundings and reduces the safety distances required by the heater. A stove that is integrated into the deck should be equipped with an external control panel to make it easy to operate. The control panel can be installed in the sauna room or, for example, in the dressing room.

Top left: IKI-Kiuas Oy 7,5 kW, top right: IKI-Kiuas Oy 9 kW Monolith, bottom left: IKI Corner Stove 6 kW and IKI Wall Stove 6 kW right

5.0 Round, corner or wall-mounted?

Recessing a stove always requires some space in the lute due to the frame structure and the safety distances between the stove and the lute. If the available space allows, a circular pillar stove is often the first choice. Round 6 kW stoves have a diameter of 240 – 320 mm and require a total space of 550-600 mm including safety clearances. For a 7.5-12 kW stove, 650-700 mm are required. IKI’s Corner and Wall models, for example, require only 400-500 mm of space in the depth direction. This is why they are often used in saunas that are so small in depth that it is not possible or sensible to install a circular stove.

Wall-mounted stove: the top photo shows the opposing seating and the large L-shaped laude. The width of the spaces is suitable for the chosen lude model, but the depth is too small for the rounded pillar stove. In the opposite lutes, the circular stove is almost immediately after the access opening and in the L lute it is too close to the access passage. A better solution in both cases is the IKI Wall Stove, which is 540 mm wide but only 300 mm deep. IKI Wall electric heaters can be installed directly against the panel wall of the sauna. The safety distance from the front edge of the heater to the ceiling is only 100 mm.

Corner stove: above is the sauna, which measures 1800mm *1425 mm. The round pillar heater does not allow for an L-shaped lude, as the 6 kW pillar heater requires approximately 550 mm of space between the outer edge of the armrest and the surface of the door wall. However, with the IKI Angle 6 kW stove, an angled stove is possible. The angle stove can be installed directly against the panel wall, thus requiring less space than the circular model. This gives room for creative design of the stove: the radius of the corner stove is only 300 mm and the safety distance from the front edge of the stove to the ceiling is 100 mm. When designing your sauna with a pillar heater, you should consider IKI’s Corner and Wall models, for example, in a small space. The right choice of heater can solve even the most difficult design problems!

6.0 In summary, what is a good heater?

Choosing a stove is a process that involves considering not only the appearance of the stove, but also its location in the sauna, safety distances and the required power in relation to the size of the sauna. You should be very careful if there are a lot of glass and stone surfaces in the sauna. A good stove is the right size in terms of power, safe to fit into the sauna and, of course, pleasing to the eye. All stoves from all stove manufacturers are CE marked and safe to use, so you can make your choice based on your own preferences.

When you ask us for a quote for a stove, we will also recommend a suitable stove for your space.

Previous articles in the Sauna Design section:

Part 1. Costs

Part 2. Design of a home spa

Design programme