A Buyer's Guide To Sauna Heaters

The size of your sauna heater depends on the internal volume of your sauna. Start by calculating the actual volume (length x width x height). However, don’t forget to account for factors like insulation and glass surfaces, which increase the “computational” volume. For example, saunas with poor insulation or large amounts of glass may require up to 50% more heating power. A general rule is to add 1 cubic meter to the computational volume for every square meter of glass.

You can find the recommended sauna room size for each individual heater model in the product description. The below table indicates how this typically looks like (this varies between heater manufacturers and model to model, so please check the individual product):

You can also use Finnmark's sauna heating calculator to help you choose the right heater for your sauna.

If your sauna’s volume is borderline, it’s better to choose a slightly larger heater. It’s easier to reduce the heat output of an oversized heater than to struggle with one that’s underpowered. Just make sure the minimum required safety distances outlined in the product specification for each model are respected.

Wood-Burning Sauna Heaters

• Authenticity: Ideal for traditional saunas, offering a natural flame and a cosy atmosphere.
• Installation Requirements: Requires a flue kit and heat shielding. Consult a HETAS-certified professional for safe installation.
• Maintenance: Wood-burning heaters demand regular feeding with firewood when in use, and cleaning the ashes after each use as well as regularly checking and cleaning the flue or chimney kit.

Electric Sauna Heaters

• Convenience: Easy to operate and maintain. Perfect for home saunas with access to electricity.
• Power Supply: Check your home’s electrical capacity. Most UK homes with single-phase power can handle heaters up to 9kW. Some 9kW, and larger models may require a three-phase supply. Please check the electrical requirements for each individual product. Electric heaters must always be installed by a certified electrician.
• Control Options: Electric sauna heaters are available with integrated controls, external control units, or Wi-Fi compatibility, allowing for convenient timing and heating adjustments. 

Heat shielding is crucial when minimum safety distances between the heater and combustible materials cannot be maintained. For wood-burning sauna heaters, this may include:

• Walls and Benches: Use wall and ceiling heat shields or ensure walls are built from non-combustible materials, like stone or tiles. Even in these cases, heat shielding may be required. 
• Floor Protection: An installation base should be used when the heater is installed on a wooden floor. 

Electric heaters typically have fewer shielding requirements but always check the manufacturer’s safety guidelines and adhere to these.

The choice of sauna stones impacts the heat and the "löyly" (sauna steam/sauna atmosphere).

Recommended Sauna Stones: Opt for high-quality and durable sauna stones, like Olivine Diabase or Vulcanite. These stones are known for their durability and heat retention. 

Stone Capacity: Heaters with a high stone capacity create a soft, pleasant steam (löyly). Check the heater's specification for the required stone amount and size. 

Yes! Pouring water over the stones is key to creating the iconic “löyly.” Both wood-burning and electric sauna heaters are designed to handle ladles of water throughout the sauna session. Just ensure the stones are arranged properly, so water evaporates efficiently without damaging the heating elements.