What is the Best Wood to Use in a Sauna? A Comprehensive Guide

Choosing the right wood for a sauna is one of the most important decisions in its construction. From aesthetics to durability, temperature conduction, and even aroma, the type of wood you select will affect both the experience and longevity of your sauna. In this blog, we will discuss the best woods used in saunas, evaluate them on several key criteria, and rank them from best to worst, with Thermo Aspen taking the top spot.

Why is Wood Used in Saunas?

Wood is the preferred material for saunas due to its natural insulation properties, low heat conduction, and ability to withstand high temperatures and humidity. Other materials, such as metal, plastic, or stone, either become too hot to touch or fail to provide the comfortable, relaxing environment that saunas are known for. Wood also adds to the aesthetic appeal of the sauna, creating a natural, calming atmosphere with pleasant aromas.

What is Thermo Wood and Thermally Treated Wood?

Thermo Wood, or thermally treated wood, undergoes a high-temperature treatment process that improves its durability and moisture resistance, making it ideal for sauna use. During the thermal treatment, the wood is heated to temperatures between 180°C and 230°C in a low-oxygen environment. This process stabilizes the wood, reducing its ability to absorb moisture, and increases its resistance to rot, decay, and warping.

Benefits of Thermally Treated Wood

• Durability: The wood becomes more resistant to rot, decay, and moisture, making it last longer in a sauna environment.
• Stability: It absorbs less moisture, meaning it is less likely to warp or crack over time.
• Aesthetic: The process gives the wood a warm, rich colour, enhancing the sauna’s overall appearance.

Downsides of Thermally Treated Wood

• Higher Price: The thermal treatment process is lengthy and increases the cost of the wood.
• Fragility at High Temperatures: If wood is kiln-dried beyond a certain point (e.g., moisture content below 6%), it can become fragile, leading to cracks or reduced longevity.

Best Woods for Sauna Use

Let’s explore the different wood types commonly used in saunas, ranked from best to worst based on price, durability, temperature conduction, smell, longevity, and resistance to heat.

1. Thermo Aspen (Ranked #1)

• Price: Moderate to high
• Durability: Excellent
• Temperature Conduction: Excellent – stays cool to the touch
• Smell: Mild, pleasant
• Longevity: High – resists moisture and warping
• Resistance to Heat: Excellent
• Aesthetic: Warm, rich colour due to thermal treatment
• Origin: Finland and other Scandinavian countries

Thermo Aspen is the top choice for saunas. Its thermal treatment ensures long-term durability, resistance to moisture, and low heat conduction, making it safe to touch even in high temperatures. The aesthetic appeal, combined with a mild aroma, makes it a standout choice for luxury saunas.

2. Cedar

• Price: Moderate to high
• Durability: High
• Temperature Conduction: Low – stays cool to the touch
• Smell: Strong, natural aroma
• Longevity: High – naturally resists decay and moisture
• Resistance to Heat: Excellent
• Aesthetic: Light to reddish tones
• Origin: North America (Western Red Cedar)

Cedar is a popular sauna wood known for its distinct aroma and high durability. Its ability to stay cool to the touch and its natural resistance to moisture make it a strong contender, though the aroma may be too intense for some users.

3. Alder

• Price: Moderate
• Durability: Good
• Temperature Conduction: Low
• Smell: Mild, sweet
• Longevity: Moderate – reasonably resistant to heat and moisture
• Resistance to Heat: Good
• Aesthetic: Reddish tones with smooth texture
• Origin: North America, Europe

Alder is a great all-around option, with a pleasant aroma, attractive appearance, and good resistance to heat and moisture. It ranks third for its balanced performance and moderate cost, making it ideal for those seeking a balance between aesthetics and functionality.

4. Hemlock

• Price: Moderate
• Durability: Good
• Temperature Conduction: Low
• Smell: Mild, neutral
• Longevity: Moderate – less moisture-resistant than Cedar or Thermo Aspen
• Resistance to Heat: Good
• Aesthetic: Light, fine grain
• Origin: North America

Hemlock is an affordable option for sauna construction, offering decent heat resistance and a neutral aroma. However, it doesn’t match the longevity and durability of higher-end woods like Thermo Aspen or Cedar.

5. Spruce

• Price: Low
• Durability: Moderate
• Temperature Conduction: High – can get hot to the touch
• Smell: Mild, slightly resinous
• Longevity: Moderate
• Resistance to Heat: Fair – can warp over time
• Aesthetic: Light, rustic appearance with visible knots
• Origin: Scandinavia, North America

Spruce is a budget-friendly wood often used in saunas but comes with some limitations, such as lower heat resistance and a tendency to warp. Its rustic appearance, combined with visible knots, may appeal to some but requires more care and maintenance over time.

Benefits of Low-Knot Wood in Saunas

Low-knot wood is highly preferred in sauna construction due to several benefits:

• Durability: Fewer knots mean fewer weak points in the wood, reducing the chance of cracking or splitting over time.
• Aesthetic Appeal: Low-knot wood provides a smooth, clean surface that many find visually appealing.
• Heat Resistance: Knots can expand and contract at different rates compared to the surrounding wood, making the surface uneven and potentially uncomfortable in high-heat environments.
• Water Resistance: Wood with fewer knots is less likely to allow water to seep through, helping maintain a dry and durable sauna environment.

Maintenance and Care of Sauna Wood

To extend the life of your sauna wood, proper maintenance is essential. Regular cleaning, combined with periodic oiling, can help prevent the wood from drying out or becoming damaged over time. Soft cloths and gentle, sauna-safe cleaners should be used to avoid harsh chemicals that might damage the wood.

Conclusion: The Top 3 Woods for Sauna Use

1. Thermo Aspen: The best overall for its durability, heat resistance, and aesthetic appeal.
2. Cedar: A close second due to its natural resistance to moisture and unique aroma.
3. Alder: A balanced option with good heat resistance and a pleasant aroma.

Thermo Aspen takes the number one spot because of its thermal stability, resistance to moisture, and excellent performance in the sauna environment. Its rich appearance and long-lasting properties make it a top choice for those looking to create a high-quality sauna.

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Bibliography

1. Finnish Sauna Society. “The Benefits of Thermo Wood in Saunas.”
2. Western Red Cedar Lumber Association. “Properties of Cedar for Sauna Construction.”
3. Journal of Wood Science. “Heat Resistance and Durability of Different Sauna Woods.”
4. North American Forestry Association. “Sourcing and Sustainability of Sauna Woods.”
5. Mayo Clinic Proceedings. “The Role of Wood in High-Heat Environments.”