Getting The Best From Sauna – Part II – The Sauna

The sauna itself and how it’s designed is important to getting the most enjoyment and benefits.

There’s a saying among folks in Europe, particularly Finland, that ’90% of the saunas in America are bad, and the other 10% are worse’. Sadly there’s a lot of truth in that, not just for America but the UK as well.

A real, properly designed and built sauna not only provides us with a much more enjoyable experience and one that we’ll not grow tired of as we so often do with the poorly done saunas, but it will also likely result in our achieving better recovery and health benefits.

What Is A Sauna?

A Sauna is more than just a hot room. It’s a very specific and unique bather experience that includes among others the following core characteristics:

  1. Even Convective Heat. We are heated evenly by a hot air bath of soft convective heat that caresses our entire body; head to toes, front to back and minute to minute. Every inch of our body is enveloped evenly by this hot air – we are bathed in hot air. Ideally we should experience no more than about a 15% head to toes temp difference but as much as 20% is still OK. 
  2. No Noticeable Radiant Heat. Particularly from the heater but really any that is noticeable except for perhaps a very mild bit on our back.
  3. Continuous Fresh Air To Breath without high levels of CO2, Pathogens, VOC’s or odors. 
  4. Hygienic – We are not exposed to unhealthy levels of bacteria, mold or other harmful elements.
  5. Steam – In a Finnish sauna we can throw water on the stones while a bio-sauna has continuous steam production. This steam then descends from the ceiling and evenly envelopes our entire body head to toes. In a Finnish sauna it is exhausted somewhat quickly (so that we can do it again!).
  6. Cooldown – Options for cooling down between rounds in the hot room.
  7. Enjoyable and Social – Sauna is a social endeavor and whether alone or with friends should always be enjoyable.

These are some of the critical elements that have made saunas so popular in Europe. If you want a sauna, and the benefits that come with it, then achieving this bather experience is key and very much worth the effort.

A Compelling Experience – We should not give short shrift to this. If our sauna does not provide a comfortable, enjoyable and compelling experience – one that we’ll desire to enjoy consistently multiple times per week for life, then as the novelty wears off, so to will our desire to use the sauna and benefit from it. This is a common problem with poorly done saunas throughout the English speaking world. Cold feet and stale suffocating air are not enjoyable.

Now let’s look at the key design elements of a sauna, how they achieve the bather experience we want and how these together are critical for our goals.

  1. Feet ABOVE The Stones
  2. Feet ABOVE The Cold Zone
  3. Ventilation
  4. A Larger Room
  5. Changing Area
  6. Cooldown Options
  7. Showers
  8. Steam


[Do one image for each of these?]

1. Feet ABOVE The Stones

Finns call this ‘the first law of lóyly’ and for a number of good reasons is one of the most critical elements of sauna design. It is also the most missed design element in the English speaking world.

[photo of 3 bench sauna with labels for Sitting & Foot benches- Saunas in Europe almost all have 3 bench levels or steps up to a high platform to get bathers feet higher.]

The foot bench (the highest bench is called the sitting bench, the bench below that is the foot bench and below that are step benches) should always be above the top of the heater stones, ideally by about 20cm (8”) or more. And yes, this requires a ceiling of about 260cm (8.5’) or higher.

The reason for this is not for hotter heat, but for more even heat. So our head to toe temps are more even and so our entire body feels the steam when it’s created. We want no more than about a 20% difference and ideally about 15%. More than 20% is known as ‘cold toes’.

For Finn’s this is primarily a comfort issue – sauna is much more comfortable and enjoyable when our feet aren’t much cooler than our head. There are also implications for health and recovery benefits.

The higher ceiling also creates a heat cavity above the door that retains heat when the door is opened which is more comfortable and more energy efficient.

For Our Goals:

Hygiene – The only way to kill most bacteria on or in a wood surface is heat. The foot bench is a key bacteria factory and needs to maintain about 60-65°c (140-150°f) which is not possible with lower benches.

Core Temp – This may be critical for getting our core temp high enough. Remember [ref previous] that how long we stay in is determined by the heat at our head. Greater head to toes temperature difference means less average skin temp exposure and less core temp change. Similarly, not having our full body up in the steam could significantly decrease core temp change.

Localized Heat – This results in our hips, legs and feet being exposed to higher temps for a longer period of time.

Contrast Therapy – Getting our entire body, head to toes and core, all fully and evenly heated like this results in not just a more beneficial contrast when we jump in a cold plunge but a much more enjoyable experience. If you’ve only done cold plunges after being in a low bench sauna or barrel then you’re in for a treat when you try it after a real sauna!

More Comfortable – We’ll enjoy it more but critically for health we’ll stay in longer and get more benefit from the heat.


2. Feet ABOVE The Cold Zone

Our entire body, and so the foot bench, should be above the lower third of the volume of space (height in a typical cabin sauna). This even if the top of the stones is a lower. Our entire body should be in the upper 2/3’s of the space.

The lower third of a sauna is simply too cool and steam doesn’t descend down, even if the stones are lower.

Note: A circulating heater such as a Saunum can be an option for situations where the ceiling cannot be high enough to get the foot bench above the stones and cold zone. While not as good as a proper sauna, this is better than having cold feet.

For Our Goals: Same as above.


3. We Need To Breathe

Stuffing people in a small space like a sauna results in high CO2 from exhaled breath that needs to be removed.

Our goal is to keep CO2 below about 700 ppm. If CO2 is maintained below 700 ppm then other contaminants are usually kept at healthy low levels as well.

We need about 9-12 l/s (20-25 CFM) per person of ventilation in our saunas to remove exhaled CO2 and other contaminants.

Downdraft ventilation, where fresh air enters above the heater and is exhausted from under the benches or near the floor works best and also helps to reduce temperature and steam stratification.

Note that electric heated saunas need mechanical exhaust such as an electric duct blower and sometimes also mechanical fresh air supply. Mechanical exhaust should be from below the foot bench.

We know that building muscle requires tearing muscles apart and then allowing our body to repair them. This repair process requires energy which is derived from ATP production from glycolysis. CO2 is a necessary waste product of glycolysis. Once generated, CO2 is carried in our blood to our lungs and exhaled. How much is exhausted with each breath depends on the CO2 level of the air we’re breathing in.

The higher the ambient CO2 level in the sauna, the less our body can expel with each breath. If we can’t rid our body of CO2 fast enough then our brain tells our cells to slow down metabolic processes so that they produce less CO2. This means that repairing of muscle fibers is slowed down.

One of the best ways to know CO2 in a sauna is to use an Aranet4 or similar and place it just below the foot bench (temp needs to remain below about 50°c).

For Our Goals:

Hygiene – Besides CO2, proper ventilation is critical to removing other harmful gook including airborne bacteria (and it’s odors) and pathogens.

Muscle Recovery/Building – Our body is able to exhaust sufficient CO2 to allow for maximum recovery. If CO2 levels are too high then we might be better off staying away from the sauna.

Heat Exposure – Reduced stratification results in better core and local heating.

Heat Exposure Time – When our time in the sauna is more comfortable and enjoyable we want to stay in longer and so we’ll be exposed to beneficial heat longer.

Comfort/Enjoyment – Fresher air and more even head to toes temps makes our time in the sauna more comfortable and enjoyable.


4. Bigger is (mostly) Better

A good sauna hot room should be about 250x250x260cm (8’w x 8’d x 8.5’h) or larger. This is a good size for one to four people and is the recommended minimum even for just a single person. Anything below about 180×180 (6’x6’) is likely to not be used much beyond the novelty period.

As well, the heater should be some distance from bathers. As a general rule the foot bench should be at least 90cm (3’) from the heater. (this should be a proper sauna heater, not a heavy steel stove or conversion.)

We want at least 3-4 m³ (100-150 cubic feet) of volume per bather. So for 6 people we’d want about a 300x300x275 (10’x10’x9’) interior.

This results in:

  • More even and comfortable heat and steam.
  • Fresher air to breath.
  • Less radiant from the stove.
  • Less uncomfortable radiant from the front and side walls. 
  • Less likelihood of heat rising in to our face.
  • Less likely to feel claustrophobic

Every cm less, even for just one person, reduces the sauna experience.  Smaller is sometimes necessary due to space constraints but for the best experience reduce as little as possible.

For Our Goals:

Heat Exposure – More even heat results in better core and local heating.

Comfort/Enjoyment – We’ll stay in longer and benefit from the heat more. The role that size plays in comfort and enjoyment should not be underestimated.


5. Changing/Shower/Rest Area

Critically this provides an air-lock between the hot sauna and cold outside that reduces cold drafts on bathers and reduces energy costs.  It provides a space to pre-warm our body before entering the hot sauna.  So though it’s called a ‘changing room’, it’s much more than that.

This should be a space that’s pleasant to hang out in for a few hours (not a locker room or garage) and include windows and doors to outside.

For Our Goals:

Comfort/Enjoyment – We’ll stay in longer and benefit from the heat more (and we’ll not be wasting as much money on heating costs which might help us to relax a bit).


6. Cool Down Options

There’s no contrast therapy without this and cooling down between rounds in the hot room is truly one of the greatest joys of sauna.

A variety of options is ideal including a nice area to sit outside, similar area inside, a cold plunge pool (≈18°c / 65°f), or being able to jump in a lake or the sea. These should all be easily accessible from the sauna without long treks through our house or a public reception area at a club.

For Our Goals:

Contrast – This is likely critical to many or most recovery and health benefits.

Comfort/Enjoyment – We’ll stay in longer and benefit from the heat more.


7. Showers

It’s critical to rinse under a shower before each round in the sauna hot room and sometimes twice per round. We’ll typically shower 4 or 5 times in a session of three rounds.

Rinsing sweat off before relaxing inside or outside make these much more comfortable. Water dries off our skin quickly, sweat not so much.

These should be located near the sauna as we’ll be walking wet between the sauna and showers. These are typically fairly open to semi-private. Easy to quickly step in and out of without curtains or doors to deal with. Experience showers can add some fun.

For Our Goals:

Hygiene – Make it easy and convenient! For ourselves and others sharing the sauna with us we want this to be as easy as possible. We want people to wash or rinse in a shower frequently.

Contrast – Lacking a cold plunge, lake, or roll in the snow, a shower is the best way to quickly cool down.

Comfort/Enjoyment – Being able to very easily shower frequently, to rinse off sweat or cool down, makes the overall experience much more enjoyable.


8. Steam

Yes, this is safe and you won’t get electrocuted.

This is one of the best bits of Finnish Sauna and for me second only to the endorphins rush of jumping in to a cold plunge.

In a Finnish Sauna it’s typical to throw a ladle of water on the stones two or three times per 15 minute round. A Bio Sauna, which is lower temp, will have constant moderate humidity from either a continuous drip or a small steam generator in the heater.

Though it feels like the temp jumps up dramatically, it doesn’t. Steam or more humid air transfer heat to our body more efficiently and faster than dryer air so it feels like the air temp changed even when it didn’t

ALWAYS use clean tap water.

For Our Goals:

Heat – Bursts of steam in a Finnish sauna transfer a lot of heat to our body in a short period of time to raise our core temp or provide localized heat.

Enjoyment – This is truly one of the most enjoyable bits of sauna.


Some other things to consider:

There are a number of other bits that make a sauna more comfortable, enjoyable and beneficial including the overall shape, sufficient air gaps in the benches and a drain. The walls, ceiling and benches should of soft wood for its hygroscopic and noise quieting properties. 


Thermal Suites

The sauna hot room itself is actually kind of a minor bit of the overall experience.

Outside of the U.S. it’s common, in both public spaces and private residences, to have a Thermal Suite or ‘Sauna Landscape’ dedicated to sauna and other thermal experiences.

These generally have a larger central area with a plunge pool and loungers for relaxing between rounds in the sauna hot room. This also acts as the air lock and has an exit to an outdoor patio (and maybe hot tub) for cooling off outside.

The Finnish sauna will be a room off of this central area and will usually have showers directly by the sauna entrance.

A steam bath or caldarium, laconium and tepidarium are often included. Or in a private residence these can be combined in one space. A larger public sauna landscape or sauna world will often also have a dedicated bio sauna separate from the Finnish sauna.

There is no better way to spend a few recovery hours after a workout!


Trumpkin’s Sauna Notes


‘Secrets of Finnish Sauna Design’