As a rule, a heater is selected based on the volumetric dimensions of the sauna room. The functioning of heaters manufactured by IKI-Kiuas (the parent company) is based on the heat retention capacity of a large amount of stones. This means the heater’s power capacity requirement is not greatly affected by stone and glass surfaces in the sauna room. However, if there are a lot of stone or glass surfaces in the sauna, it is advisable to choose a more powerful model if the volumetric dimensions of the room are close to the limits.

Log walls heat up slowly, so a more efficient heater should also be selected in this case. When choosing the appropriate heater, it is advisable to ask the reseller or IKI-Kiuas technical support for advice. Keep in mind that the walls and ceiling of the sauna room must be well insulated. All surfaces that store heat must be thermally insulated.

10.76 sq. ft (1 sq. m) of uninsulated surface in the ceiling or on the walls increases the heater’s power requirement. As a rule of thumb, add 42.4 cubic ft (1.2 cubic meters) to 53 cubic ft (1.5 cubic meters) to the room volume for every 10.7 sq. ft (1 square meter) of uninsulated surface. In saunas with glass surfaces and walls, it is especially important to carefully calculate the heater’s power requirement in relation to the volumetric dimensions of the room.

The height of the sauna room should be relatively low. The higher the room, the more powerful the heater needs to be, as additional height increases the room’s volumetric dimensions. Because warm air rises, the recommended height between the seats and the ceiling is a maximum of 4 ft (1200 mm).

If the heater is not powerful enough, the temperature in the steam room will remain too low. In this case, sauna-goers often try to raise the temperature by throwing more water onto the heater. This quickly cools down the stones, and ultimately no steam can be produced from a tepid heater.

The sauna stones should be placed carefully into the heater. The distance between the resistors and the mesh frame should be completely covered by stones, all the way around and to the top of the heater. However, the stones must not be stacked too tightly; there needs to be slight gaps between the stones to ensure unobstructed air circulation.

In privately used saunas, we recommend using olivine, olivine diabase or peridot stones. The stones should be less than 4 inches in diameter, making them easy to stack between the heater’s frame and the resistors.

Over time deposits from infusion water and fragrance additives clog the pores of the sauna stones. This reduces the heat storage capacity of the stones, which is why we recommend changing the sauna stones once a year in commercial and/or intensive use heaters. At the very latest, if you notice a decrease in the heat output of the heater and/or the stones are becoming porous and breaking, it is high time to replace them.

NOTE! When laying the stones, make sure that the resistors ARE NOT in contact with one another or the outer casing of the heater.

According to building regulations the minimum height for a sauna room is 6.2 ft (1900 mm). Usually anything between 6.5 – 7.5 ft (2000 – 2300 mm) is good. The room height affects energy consumption and increases heating time. Thus, room height also affects the heater’s power requirements. The required power of the heater is calculated based on the cubic volume of the sauna room. The recommended height between the upper bench and the ceiling is a maximum of 4 ft (1200 mm).

Proper thermal insulation of the walls and the ceiling structures play a significant role in retaining a steady temperature inside the sauna room. The better the insulation, the lower the energy required for heating. Therefore, special attention should be paid to the U-value of the materials used for thermal insulation. Thin materials often have low U-values, despite “increasing” the space inside the room.

All heat-storing surfaces must be thermally insulated in the same way as the walls. Uninsulated surface in the ceiling or on the walls increases the heater’s power requirement by 1.2. With regards to uninsulated surfaces, it is always advisable to read the manufacturers’ operating instructions. Often a good rule of thumb is that 10.7 sq. ft (1 square m) of uninsulated surface adds 13 – 16 sq. ft (1.2 to 1.5 cubic meters) to the room’s volumetric dimensions. If there are glass surfaces and walls in the sauna room, it is important to carefully calculate the power requirements for the heater in relation to the volumetric dimensions of the room.

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Choose the correct stove model carefully. Prolonged use of a heater that is not powerful enough may shorten its lifespan. Note that all uninsulated surfaces on the walls and the ceiling (e.g. brick, glass, tile, concrete) increase the need for heating capacity. When calculating the sauna room’s volumetric dimensions, you need to add approximately 13 sq. ft (1.2m3) for each uninsulated 11 sq. ft (1 m3). If the walls are solid log, the volume should be multiplied by 1.5.

As an example:
– A sauna room the size of 108 sq. ft (10m3) with one brick wall measuring 6.6 x 6.6 ft (2 by 2 meters) corresponds to 161 sq. ft (15m3).
– A sauna room the size of 108 sq. ft (10m3) with solid log walls also corresponds to 161 sq. ft (15m3).

The stones should be placed carefully. The stones must not be stacked too tightly; there need to be slight gaps between the stones to ensure unobstructed air circulation. We recommend the use of basic sauna stones (e.g. olivine diabase) no larger than 4 inches (10 cm) in diameter. 

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