A traditional sauna offers a uniquely soothing experience, blending age-old wisdom and modern principles to create the ideal space for relaxation and rejuvenation. Inspired by Trumpkin’s Notes on Sauna Building, this guide presents everything you need to know about crafting a sauna that prioritizes comfort, health benefits, and authenticity.

What Sets a Traditional Sauna Apart?

A true traditional sauna delivers a gentle, uniform heat that envelops your entire body, creating a tranquil "air bath" experience. The warmth is distributed evenly for a consistent, comfortable experience from head to toe. Avoid saunas with harsh radiant heat.

Here’s what defines the experience:

1. Customizable Temperatures: Adjust the warmth to your liking within a range of 160–230°F, with an ideal variation of ±59°F.
2. No Harsh Radiant Heat: The heat isn’t harsh or direct—it’s soft, consistent, and evenly spread.
3. Fresh, Clean Air: Proper ventilation ensures low CO2 and VOC levels, making breathing easy and the environment refreshing.
4. Steam That Enhances Comfort: Pouring water onto the stones creates steam that envelops your body in soothing heat. This dissipates quickly, allowing repeated applications.
5. No Drafts: Even when the door is opened, the sauna maintains its warmth without any sudden cold intrusions.

Dos and Don’ts for a Traditional Sauna

Crafting a traditional sauna to achieve the ideal experience requires precision and adherence to these principles:

DO:

• Ensure Proper Ventilation:
  Effective ventilation eliminates CO2, stale air, and impurities while promoting even heat. A rate of 20–25 CFM per person is recommended, with mechanical downdraft ventilation being ideal for electric heaters.
• Position Benches Above the Cold Zone:
  Elevate benches so your feet are above the colder lower third of the sauna. Ideally, your feet should rest above the heater stones.
• Maintain Distance from the Heater:
  To avoid harsh radiant heat, ensure a space between bathers and the stove, allowing for a proper convective heat loop.
• Build a Spacious Sauna:
  For optimal heat distribution, airflow, and comfort, aim for a sauna that’s 8 feet in height, width, and depth.
• Include a Changing Area:
  A separate changing area helps prevent heat loss and keeps the sauna insulated—especially useful in colder climates.

 

DON’T:

• Use low ceilings (below 7 feet), as they hinder air circulation and disrupt the convective heat loop.
• Opt for low benches, inadequate ventilation, or poor placement of the heater.

 

3 Key Heat Zones in a Traditional Sauna

A well-designed sauna operates with 3 key zones of heat, each playing a role in the overall experience:

1. Convective Loop

The sauna stove heats the stones, which then generate hot air (convective heat) as air passes through them. This warm air rises to the ceiling, travels horizontally towards the far bench wall, and then descends along the bench wall, warming our bodies as it flows. This continuous air movement forms a convective loop, which ensures even warmth around us.

When water is poured onto the stones, it produces steam that follows this convective loop, descending and briefly intensifying the heat we feel. This process, particularly the movement of steam, is essential for a good sauna experience and is referred to as the Löyly Cavity or Löyly Pocket.

2. Thermal Stratification

Thermal stratification occurs when hotter air rises because it is lighter, while cooler air sinks due to its density. In a sauna, this creates a temperature gradient between the floor and the ceiling.

To minimize this effect and achieve more even heating:

• Use higher ceilings and benches to reduce the temperature difference from head to toe.
• A well-functioning convective loop can help circulate the air more effectively.
• Implement downdraft ventilation to balance the airflow.

Positioning benches higher above the colder air near the floor and staying in the descending airflow rather than the rising air near the heater can ensure a more comfortable and consistent experience.

3. Cold Zone

The lower third of the sauna, where the air temperature is significantly cooler than at the ceiling, is referred to as the cold zone. It’s important to avoid allowing any part of your body to remain in this area to maintain comfort and warmth during your sauna session.

3 Essential Sauna Zones

1. Heat Cavity

This zone is located above the door opening and plays a vital role in trapping and preserving heat when the door is opened. A larger heat cavity is generally more effective at maintaining the sauna’s warmth.

2. Löyly Pocket (or Löyly Cavity)

Found above the Cold Zone and typically well above the stones, this area is central to creating an even, comfortable warmth. The convective loop within the Löyly Pocket minimizes temperature differences (stratification) compared to lower zones, ensuring steam rarely drops below this level.

3. Cold Zone

This is the bottom third of the sauna's height and volume, where the air is noticeably cooler. It often experiences significant temperature differences, making it important to keep your body above this area to maintain a comfortable and effective sauna experience.

Design Elements Inspired by Trumpkin’s Notes

• Feet Above the Stones:
  Keeping feet above the stones prevents "cold toes" and ensures consistent heat. This positioning also promotes hygiene, supports health benefits, and enhances overall enjoyment.
• Optimize Stove Placement:
  Place the heater and door on the same wall, with benches opposite. This configuration promotes airflow and minimizes heat loss when the door opens.
• Use Ample Stones:
  The stove should have at least 6–8kg of stones per cubic meter of sauna space. Doubling this amount improves steam quality and heat retention.
• Incorporate Fresh Air:
  Ventilation removes impurities and excess humidity, ensuring a clean, breathable environment.

A sauna offers a unique "air bath" experience, delivering gentle, evenly distributed convective heat across the body. Eero Kilpi, president of the North American Sauna Society, emphasizes that any noticeable radiant heat is undesirable in a sauna, as it disrupts the consistent warmth we seek. Similarly, Risto Elomaa, president of the International Sauna Association, agrees, stating that noticeable radiant or infrared heat is not ideal for an authentic sauna experience.

When consulting sauna experts and builders, three key principles consistently emerge:

1. Ensure proper ventilation.
2. Opt for a larger sauna space.
3. Keep your feet elevated above the cold zone.

These fundamental elements help create the ideal environment for a balanced sauna experience.

The Importance of Löyly

Perhaps most importantly, however, is the quality of the heat, referred to as löyly. This includes:

• Ensuring the temperature is uniform across the body—head to toe, front to back—and remains consistent throughout the session.
• Maintaining air that is fresh, free from excess CO2 or humidity.
• Ensuring the sauna is free of unpleasant radiant heat.
• Facilitating an even convective loop of heat and steam, flowing from the ceiling down to the toes.

Temperature as a Secondary Factor

Ultimately, the sauna's temperature is secondary to the overall löyly experience. It doesn’t matter if the sauna hits 200°F if your feet feel too cold or if the air is stale, leading to discomfort or lightheadedness.

A well-designed sauna, with proper airflow, lack of radiant heat, and consistent temperatures, can even maintain a lower temperature of 140°F without sacrificing the sauna experience.

The official temperature range recommended is between 167°F to 221°F, measured about 39 inches above the middle of the longest sitting bench, opposite the heater. However, as long as the other elements are optimized, a well-balanced sauna can offer a satisfying experience at a broader range of temperatures.

Understanding Löyly: The Heart of a Traditional Sauna

Löyly is the essence of the sauna experience. It’s not just steam; it’s the perfect balance of heat, air quality, and humidity. Achieving optimal löyly requires clean, fresh air and proper ventilation combined with a well-designed space.

When löyly is at its best:

• Heat is evenly distributed, with no noticeable hot spots or drafts.
  
• Steam from the stones feels like a soft wave of warmth descending over your body.
  
• The environment remains fresh, with no stale air or harsh radiant heat.
  
• Everyone enjoys it and feels refreshed afterwards.

Practical Sauna Size and Design Tips

Ceiling Shape:
The ceiling can be flat, coved, barrel-vaulted, cathedral, or sloped—each works well as long as the highest point of the ceiling is no more than a quarter of the distance from the heater wall to the bench wall. It’s important to avoid ceiling beams or other obstacles that could disrupt the airflow of the convective loop.

Stove Room Volume:
The recommended minimum volume is 3 m³ (105 cubic feet) per person or more. While some builders suggest 2 m³ (70 cubic feet) per person, with an additional 1 m³ (35 cubic feet) for the heater, this is less ideal. Larger volumes, between 4 to 5 m³ per person, are preferred for optimal comfort and efficiency. Smaller spaces tend to lead to poor air circulation and wasted energy.

Stove Room Shape:
The best shape for a sauna room is generally square (WxDxH), followed by rectangular or slightly taller rectangular rooms. This shape supports proper airflow and heat distribution.

 

Minimum Size:
A sauna’s ideal size starts at 8’x8’ (with a height of 8.5’). Reducing the dimensions compromises the sauna experience, even for one person. If you plan for a smaller space, anything below 8x8 should be approached cautiously, as every inch affects the overall experience. Going below 6’ (from heater wall to bench wall) and 5’ (bench width) can result in poor air quality, an ineffective convective loop, unwanted radiant heat from the stove, and a cramped atmosphere.

 

Heater and Bench Placement:
The heater generates heat that rises to the ceiling before descending on the opposite side of the room. To optimize the sauna experience, bathers should sit on the side where the heat descends. Placing the heater and door on the same wall, with the benches across from them, creates a smooth convective loop and reduces heat loss when the door is opened.

 

Bench and Ceiling Heights:
Higher bench and ceiling heights are key for better heat distribution and reducing temperature stratification. This setup helps ensure a more uniform sauna experience. The thermostat should be placed 1 meter above the highest sitting bench and at least 20 cm away from the heater for precise readings.

 

Floor Drain:
It’s highly recommended to install a floor drain in the sauna for easier maintenance. This is particularly important if you plan to use large amounts of water for cleaning or to create steam, as it ensures effective drainage and helps keep the space clean and hygienic.

Conclusion

Building a traditional sauna is an art and a science. By following these principles and drawing inspiration from Trumpkin’s Notes, you can create a space that delivers the ultimate relaxation and wellness experience. From proper ventilation and bench positioning to achieving perfect löyly, every detail contributes to the authenticity and comfort of your sauna.