[DRAFT]
Steam baths, and in particular Thermariums, pair well with saunas as part of a home or commercial thermal suite. We will almost always include one or more rounds in a steam bath if available among several rounds of sauna.
Following are some notes I’ve gathered. Unlike sauna, I have not spent much time studying steam baths in detail so these are all subject to change as we learn more.
Another good resource is the GWI Hydrothermal Guide. It’s aimed at commercial facilities but a home thermal suite is very similar and most of the design guidance applies.
Unlike saunas that are frequently not built correctly in North America and the UK, steam baths are not so bad with the two biggest errors being ceiling shape and ventilation. So here are a few things to think about.
Steam Shower Combo – Americans like to combine these because it saves some money and manufacturers push them because they just want to sell the steam generator and this makes it an easier sell, but this results in a much lessor experience so I do not recommend doing this.
That said, some people do enjoy a steamier shower experience which a combo provides. But note that this is not a steam bath experience.
FWIW, it’s not unusual to have both. A steam shower in a master bathroom as well as a proper steam room as part of the home’s thermal suite.
Separate Showers – It is always best to keep showers separate from the steam bath.
A typical thermal routine (sauna, steam bath, laconium, etc.) is to shower well (with soap before the first round), do a round in the steam bath or sauna, then shower to cool off, rest, repeat. This is impossible when the steam bath and shower are combined as a steam shower.
Showers in a thermal suite need not be an enclosed space. Two or four showers along a wall of the thermal common area works well in most cases. Or maybe two showers on a wall plus one in a more private stall. Every square meter of tiled wall is expensive so in many cases the less the better.
For a bit more privacy showers can be in U shaped stalls along a hallway and for more privacy yet the ones on the ends can be a 180° turn in to the stall.
Steam Room
Volume – A minimum volume of 3 m³ (105 cubic feet) per person is recommended though 4-6 m³ per person is better. Smaller than 6 m³ (210 cubic feet) overall should generally be avoided as it often results in uneven temps and steam.
A larger space provides for a more even and enveloping steam on bathers bodies. It does however require more labor and materials for tile and a larger steam generator.
Ceiling Height – 8’ generally works well.
Ceiling Slope – The ceiling should never be flat as that can result in drips of hot condensate on bathers. It is generally best to slope the ceiling away from the door (avoid having a waterfall across the door) at a pitch of about 1 in 7 or greater.
A cathedral, domed or hipped ceiling can work as well. Avoid having a low side along the door wall or include a gutter over the doorway to avoid condensate dripping on people.
Heat Cavity – This is the space above the door that retains heat and steam when the door is opened. The more people who will be using the steam bath (e.g., opening/closing the door letting steam out and cold air in) the more important this is and somewhat the larger it should be to avoid loosing too much heat and steam each time the door is opened. In general having the ceiling 30-40cm above the door opening will suffice.
Bench Heights -Unlike a sauna where we want to be up in the löyly cavity, this is not so necessary in a steam bath. There is still stratification and a higher bench does provide a more even and enjoyable experience but the difference is not as great as in a sauna. So a variety of bench heights and configurations can work well.
A ≈42cm (16.5”) high bench above our feet are is comfortable for most people in a steam bath.
A simple two bench system with one bench at 42cm and a second at 84cm works well.
Bench Slope (Forward) – Generally benches are sloped very slightly forward so that condensate/water do not collect on the seat.
Bench Slope (Backward) – Alternatively, the benches may slope very slightly towards the wall. This requires either a trough or a trough drain along the back edge for condensate/water runoff.
This may provide for more comfortable seating but is also a bit more complicated to construct and keep clean.
If doing an open trough there does need to be a way for the condensate to drain out so either a drain (can be a tube exiting at the floor) or have the ends of the trough exit along the sides of the seat.
Rounded Edges – The front edges of benches should always be rounded for comfort.
Lip – It’s perhaps nice to have a lip on the bench so that the skirt sits 5-10cm behind the front edge so that bathers heels are digging in to the skirt. I personally have not found the lack of this to be a significant drawback however.
Heated Floor & Benches – Heated benches make for a much more pleasant experience as do heated floors. This even if not doing a full Thermarium.
Minimize Glass – Glass not only wastes energy but makes the steam bath less comfortable. Limit glass to the door only.
Also, all those photos of wonderful looking glass steam baths… Reality, even with a good squeegee after every use, is a much dirtier glass.
Kneipp Hose – There should be one or more hoses available for bathers to rinse off their sitting area before and after they use it.
Ventilation – Packaged Systems
If you are purchasing a packaged steam bath experience system then follow the manufacturers recommendations for ventilation.
These systems often have multiple steam heads that require very specific and sometimes coordinated ventilation to function properly.
Note: If the package does not include ventilation or provides for ventilation of less than 10 l/s (20 CFM) per person then either stay away from the package or add proper ventilation.
Ventilation – Mechanical Downdraft
A steam room needs ventilation just as a sauna. There are two theories on how best to ventilate a steam bath; Mechanical Updraft and Mechanical Downdraft.
Note: The thermo and aerodynamics of a steam bath are different from a sauna and interestingly a bit trickier because we don’t have the convective loop to help us.
Mechanical Downdraft should generally work well for most steam baths so for this follow the guidelines for Mechanical Downdraft for Electrically Heated Saunas.Fresh Air Supply –
Supply Option 1 – In the ceiling.
Supply Option 2 – On the door wall about 6” below the ceiling. This should always include an updraft duct.
Mechanical Exhaust – About 8” above the floor and far from the steam supply (head) and fresh air supply.
Post Bath Ventilation –
Systems – The higher humidity of a steam bath requires a more specialized blower. Fantech PB, PBW and FR series can, I believe, all work well for steam baths.
There is also the Bathology 4xx series that for more money pairs a bit better control with a Fantech PBW.
Mechanical Room
Easily Accessible – Steam generators do require routine maintenance.
Drain – A floor drain is best if possible.
Vibration – Steam generators can transmit vibratory noise through a structure. In many cases an isolation pad on the floor with a water pan on top should be sufficient to reduce any vibration problems.
Placing the generator (in a pan on an isolation pad) on concrete is best.
Steam Generators
Size – Follow manufacturers recommendations.
It’s critical to calculate a correct ACM or Adjusted Cubic Meters based on the wall materials.
Bigger Is Not Necessarily Better – This varies by design but sometimes a too large steam generator will not run enough to maintain a good environment.
Single vs Two Stage – Two stage provides a more even proportional continuous temp and humidity but not surprisingly, costs more. If a cheap steam shower then a single stage is likely OK, if a proper steam bath then a two stage is worth the extra cost.
Water Line – Most U.S. homes today use 1/2” supply lines which can result in starving a steam generator. They don’t use a lot of water but for the short periods they are actually producing steam they need a ready supply.
A 3/4” line will insure that the steam generator has what it needs.
Water Conditioning – See manufacturers recommendations. Generally hardness should not exceed 60 ppm and total alkalinity be no more than 150 ppm.
Drain Pan – Steam generators should have a drain pain installed below them.
Auto Clean – Some steam generators include an auto-clean system
Manufacturers – Kohler, Steamist, and Klafs are good options. Mr Steam and Amerec may be good as well.
Thermarium
Walls and ceilings that can radiate heat can add to the experience with a variety of different offerings. For more see Sauna and Other Thermal Experiences in the menu above.
Adding a slight bit of radiant heat to a regular steam bath gives us a Caldarium for instance, while lots of radiant and little steam is a Laconium.
Note that balancing these can be tricky so some experimentation (yeah, rough job) might be necessary. In particularly, introducing a secondary heat source (radiant) can confuse some steam generators.
Hopefully Kohler, Kemitron or someone else will introduce a centralized Thermarium controller that controls the steam generator, various radiant surfaces and ventilation to provide a variety of experiences at the press of a button.