General Sauna Guide

A Sauna or Finnish Sauna is known for providing bathers with the following experience:

• We experience gentle, uniform convective heat that covers our entire body evenly, from head to toe, front to back, and moment to moment. The heat surrounds us like a warm embrace, creating a hot air bath sensation.
• We can select any temperature between 75-105°C (ideally within ±15°C) to feel the warmth throughout our bodies.
• There is no sensation of radiant heat emanating from the stove, ensuring a comfortable and consistent experience without any harsh or uneven heat sources.
• The sauna provides a continuous supply of fresh air, maintaining low levels of CO2, VOCs, and odors for easy breathing.
• Adding water to the stones generates steam that envelops our entire body uniformly, enhancing the sauna experience from head to toe.
• After creating steam, the humidity levels return to normal, allowing us to repeat the process without interruption.
• Even when the door is opened, there are no cool drafts to disrupt the comforting warmth of the sauna environment.

DOS and DON’TS

DOS:

SAUNA BUILDING IS NOT ONE SIZE FITS ALL GUIDE

FIRST 3 ARE EXTREMELY IMPORTANT

1. Elevation of Feet Above the Stones: Referred to as 'the first law of lóyly' by Finns, this crucial aspect necessitates a ceiling height of around 8.5 feet, a standard outside the U.S. Contrary to some beliefs, a 7 or 7.5-foot ceiling leads to discomfort, known as 'cold toes.' Ideally, the feet should be positioned at least 8 inches above the stones, often achieved with three benches or a raised platform.

2. Positioning Feet Above the Cold Zone: The foot bench should reside above the lower third of the sauna's height, ensuring the entire body occupies the upper two-thirds of the space, regardless of the stone's height.

3. Proper Ventilation: Adequate ventilation, typically around 20-25 CFM per person, is necessary to eliminate exhaled CO2 and contaminants. Downdraft ventilation, especially mechanical downdraft for electric saunas, is preferable.

4. Distance Between Heater and Bathers: Bathers should not feel any radiant heat from the stove, requiring a sufficient distance between the heater and bench walls for a proper convective loop. A minimum distance of 6 feet is recommended, although more is preferable.

5. Convection Heater: The heater should primarily produce convective heat and minimal radiant heat.

6. Spacious Room: A typical four-person sauna should measure around 8 feet wide, 8 feet deep, and 8.5 feet high, promoting even heat distribution, ample steam, and fresh air. Smaller dimensions compromise the sauna experience.

7. Adequate Changing Area: Essential, especially in cold climates, to serve as an air-lock and pre-warming space before entering the sauna.

DON'TS:

Recommendations such as 7-foot ceilings, low benches, inadequate ventilation, and heavy steel stoves are often at odds with optimal sauna design principles observed in Finland and Sweden.

7 LAWS OF LÖYLY

1. Your feet are above the stones, the ceiling is just high enough to use a vihta (sauna whisk), you feel no radiant from the heater and no upflowing hot air from the heater.
2. Ventilation removes CO2, excess humidity, airborne impurities and provides consistent pure fresh air for all bathers.
3. At least 6-8kg/m³ of stones. Twice that is better.
4. Sauna can maintain any temp from 80-105°c at bather's head and shoulders, and feet are no more than 10-20°c cooler.
5. You can pour water on the stones.
6. The sauna has a vestibule to prevent heat escaping and cold air from intruding.
7. Everyone, men, women and children, enjoys it and feels refreshed afterwards.

More about Löyly

• Löyly encompasses more than just the visible steam produced by water on the sauna stones; that's simply steam, known as "höyryä" in Finnish.
• According to a 1988 Finnish study, Löyly refers to "the purity, freshness, temperature, and humidity of the air in the sauna."
• Löyly emphasizes quality over quantity. It's the sensation of being uniformly heated from head to toe, front to back, in a convective loop that forms a Löyly cavity. The temperature at the head and shoulders ranges from 75 to 115°C. The air is clean and fresh, devoid of high CO2 levels, fragrances, mold, bacteria, or other impurities. Direct radiant heat is imperceptible. Soft wood walls and ceilings contribute to a comfortable environment, absorbing noise for a tranquil sauna experience.
• Water is applied to the stones, releasing an invisible burst of steam carried by the convective loop, enveloping bathers' bodies briefly for one or two minutes before dissipating, returning the sauna to its original drier state—ready for the next burst.
• "Löyly is more about the quality of heat than the quantity."
• How do we recognize löyly? Two methods offer insight: 1) Experience and Observation, and 2) Physics and Measurements.
• Closing your eyes, you shouldn't detect the stove's location or feel direct heat from it. Heat should envelop your entire body evenly, with no noticeable temperature difference between head and feet, front and back. When water is added to the stones, you should feel a gentle wave of warmth descending from the ceiling, embracing your body in comforting warmth from head to toe before dissipating.
• Some aspects, like even front-to-back heat and the softness of the steam, rely on sensory perception rather than precise measurement.
• “Steam added to bad stale air is just that, steam added to bad stale air, it is not löyly”
• “There is no shortcut to löyly, it is always about stones and proper ventilation”. - Jesse Hämäläinen of Narvi Sauna Heaters

Importance of Feet Above The Stones

• Comfort – Most individuals find a temperature differential of approximately 13-15% from head to toe to be the most comfortable and enjoyable. Therefore, ensuring that the feet are not more than roughly 13-20% cooler than the head is crucial. When the temperature difference reaches around 20%, people typically begin to experience discomfort known as 'cold feet,' and at a 27% difference, this discomfort is nearly universal.

• Enjoyment – Activities like a cold plunge, rolling in the snow, or simply standing outside are most pleasurable after experiencing full-body immersion in consistently even convective heat. The contrast, particularly with a cold plunge, is remarkably significant.

• Hygiene – Maintaining a temperature of about 60-65°C on the foot bench is essential for eliminating bacteria and other germs, and nearly this temperature is required to combat mold growth.

• Health / Medical – To reap the majority of health and medical benefits, it's crucial for the entire body to be evenly enveloped in convective heat. A temperature difference of 22% from head to toe appears to be the maximum tolerable level. If the head registers at 100°C (212°F) while the lower body remains significantly cooler, exceeding about a 22% difference, the lower body may not receive the localized musculoskeletal benefits, nor will the core temperature increase sufficiently for benefits requiring a rise in core temperature.

• Homeostasis – Our body naturally seeks homeostasis and continuously strives to achieve it. A considerable temperature difference from head to toe disrupts this balance.

• Prevention of Dry Cracked Feet – Elevating the feet into the steam can alleviate issues with dry, cracked feet, especially during the winter months.

Sauna provides an 'air bath' of convective heat

• According to Risto Elomaa, president of the International Sauna Association, any noticeable radiant or IR heat from a source "is undesirable" in a sauna.
• Eero Kilpi, president of the North American Sauna Society, echoes this sentiment, stating that "if you can point to a source, then it is undesirable" regarding radiant heat.
• When consulting sauna builders and experts in Finland, three consistent themes emerge: 'feet above the stones,' 'ventilation,' and 'bigger is better.'
• Equally, if not more crucial, is the quality of the heat and environment – known as löyly. This entails ensuring that temperatures on bathers' bodies are fairly uniform from head to toe, front to back, and minute to minute. Additionally, the air should be fresh, devoid of high levels of exhaled CO2 or accumulated humidity. Bathers should experience the convective loop and steam of the löyly cavity descending from the ceiling to their toes, with no undesirable radiant heat. These elements constitute löyly. It matters little if the sauna temperature "reaches 200°F" if feet are only 140°F, bathers experience uneven roasting due to radiant heat from the heater, or they feel lightheaded due to poor air quality.
• The officially recommended temperature range is 80-105°C (± 10°C) (167-221°F (± 20°F)), measured at a point 1m (39”) above the middle of the longest sitting bench opposite the heater. A well-designed sauna should be capable of maintaining any temperature within this range. However, if all other parameters are optimal (such as fresh air, no radiant heat from the stove, and even head-to-toe temperatures/steam), temperatures as low as 60°C could still be considered suitable for a sauna experience.

Sauna’s 3 Heat Zones

Convective Loop:

The stove heats the stones, which, in turn, generate hot air (convective heat) as air flows through them. This hot air rises to the ceiling, moves horizontally towards the far bench wall, and then descends down the bench wall, warming us as it does so. This continuous movement of air forms a convective loop, evenly warming our bodies on all sides. When water is thrown on the stones, it creates steam, which flows with the convective loop, descending on us and temporarily increasing the heat we feel. This convective loop, particularly the part involving steam, is crucial for a good sauna experience and is known as the Löyly Cavity or Löyly Pocket.

Thermal Stratification:

Thermal stratification occurs when hotter, lighter air rises, and cooler, denser air sinks. In a sauna, this results in a temperature difference between the floor and ceiling. Overcoming stratification and achieving more even temperatures can be facilitated by higher ceilings and benches, a well-functioning convective loop, and downdraft ventilation. A higher ceiling reduces the temperature difference from head to toe and allows benches to be positioned higher above the colder air near the floor. It's preferable to stay in the area where airflow is descending rather than where it is rising near the heater.

Cold Zone:

The lower third of the sauna's volume, where the air temperature is significantly colder than at the ceiling. It's important to avoid having any part of our body in this cold zone.

3 CRITICAL ZONES

1. Heat Cavity: The area above the door opening, an area that contains and preserves heat when the door is opened. Generally the larger the better.
2. Löyly Pocket or Löyly Cavity: Above the Cold Zone and often well above the top of the stones. It is this convective loop that warms us evenly and thanks to the convective loop there is less stratification in the Löyly Cavity than below it and steam rarely descends below this zone.
3. Cold Zone: is about the lower third of the volume (and thus height in a typical cabin sauna) of the space. This area also often has greater temperature stratification. We want to avoid any of our body being in this area.

Other Important Sauna Considerations

Stove Room Volume:
According to official Finnish recommendations, a minimum volume of 3 m³ (105 cubic feet) per person or more is advised. Builders have suggested that if necessary, a minimum of 2 m³ (70 cf) per person plus an additional m³ (35 cf) for the heater (yes, it's important) is also feasible, though not ideal. Larger volumes (4-5 m³ per person) are preferable, while smaller ones may result in diminishing returns and energy wastage.
Minimum Size:
A good minimum size for a sauna is about 8’x8’ (x 8.5’ high). Any reduction compromises the sauna experience, even for a single person. Going below 8×8 should be done with caution, as every inch counts. I wouldn't recommend going below 6’ (heater wall to bench wall) x 5’ (bench wall width), as it may lead to air quality issues, poor convective loop, radiant heat from the stove, and a cramped feeling.
Stove Room Shape:
An approximate square shape (WxDxH) is generally considered best, followed closely by a rectangle or slightly tall rectangle.
Ceiling Shape:
Ceilings can be flat, coved, partially barrel vaulted/curved, vaulted/cathedral, or sloped/shed, all of which can work well. However, it's essential to ensure that the highest point of the ceiling relative to the walls is not more than about 1/4 the distance from the heater wall to the bench wall. Avoid elements like ceiling beams that may interrupt the airflow of the convective loop.
Heater and Bench Relationship:
The heater heats the air near it, causing it to rise to the ceiling and then descend on the opposite side of the space. Ideally, bathers should be on the descending side of this airflow. Placing the heater and door on the same wall, with benches on the opposite wall, helps to maintain a good convective loop and minimize heat loss when the door opens.
Bench and Ceiling Heights:
Higher bench and ceiling heights are critical for a good sauna experience, as they result in less stratification, more even heat distribution, and a larger heat cavity. Thermostat placement should be at a height equal to 1m above the upper sitting bench and at least 20cm away from the heater for accurate temperature readings.
Floor Drain:
A floor drain is highly recommended for easier cleaning. Some consider it critical, especially if you want to be able to wash in the sauna, throw a lot of water on the walls and benches.