Steam bath as part of a home thermal suite.
Note: Discussion on Thermal Suites has been moved to: Thermal Suites.
Steam baths, and in particular Thermariums, pair well with saunas as part of a residential or commercial thermal suite. When we visit various therme we will almost always include, among numerous sauna rounds, one or more rounds in a steam bath if available.
Following are some notes I’ve gathered from various projects. This is far from exhaustive but will hopefully provide some info to help people to have a better steam experience.
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.
Fun science bit… What you see in a ‘steam bath’ isn’t steam, but fog. Steam is a vapor and thus invisible, fog is comprised of water droplets that are usually visible.
Unlike saunas that are frequently built incorrectly in North America and the UK, steam baths themselves are not so bad with the biggest errors being ceiling shape, poor ventilation and benches not sloped properly. So here are a few things to think about.
Steam Baths Are Social – Steam baths, or ideally a full thermal suite, are a wonderful way to enjoy some relaxing time with friends and family. Placing them in a public area rather than in a master bath is a good move.
Steam Shower Combo – Americans like to combine these because they think that 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 not so good experience so I do not recommend doing this. As to saving money, if you don’t use it after the first year then you’ve definitely not saved any money.
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 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 difficult/impossible when the steam bath and shower are combined as a steam shower.
Shower Cubes, Sauna and Steam Bath for a home Thermal Suite.
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 semi-private stall. Every square meter of tiled wall is expensive so in many cases the less the better. It’s important to make it as easy as possible to get in/out of the shower so doors/curtains should be avoided.
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 or ≈5x5x8′) overall should generally be avoided as it often results in less even temps and steam.
A larger space, like 250x250x250cm (8x8x8’) or larger, provides for a more even, enveloping steam on bathers bodies and a more pleasant experience. It does however require more labor and materials for tile and a larger steam generator.
Some people also prefer to larger space to avoid claustrophobia.
Ceiling Height – 8’ generally works well but a bit more or less doesn’t seem to be a problem.
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 need 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 usually not as great as in a sauna. So a variety of bench heights and configurations can work well.
A good starting point is a 42cm (16.5”) high lower bench and 84cm (37”) high (42cm above the lower bench) upper bench.
A ≈42cm (16.5”) high sitting position (bench height above feet) is comfortable for most people. Greater than this not so much.
Bench Depth – Approx 50cm (20”) is a good starting point. However, a deeper bench of perhaps 70cm (28”) or deeper is nice to have as it allows sitting with feet up on the bench which many people enjoy. If you want to lay down then a bench surface area of at least 65cm (26”) x 200cm (6.5’) is needed.
Bench Slope (Forward) – Sitting benches can be sloped very slightly forward so that condensate/water do not collect on the seat. Be careful to not slope too much though unless you want a good isometric workout for your quads.
Bench Slope (Backward) – Alternatively, the benches may slope very slightly towards the wall. This usually 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. This reduces bathers heels digging in to the skirt. I personally have not found the lack of this to be a significant drawback however but others have.
Linear Drain – A trough or linear drain may be less likely to have problems than center drains. The flat sloped floor used with a linear drain is easier to install and less likely to have low spots in the drain field. It is safer and more comfortable to walk on compared to the four slope compound floor required for a center drain and is particularly important for people with disabilities. A linear drain is strongly recommended for curbless designs. Linear drains work much better for larger tiles.
Linear drains do require cleaning, typically every four to six months. However, a steam bath should be thoroughly cleaned somewhat frequently anyway.
Heated Floor & Benches – Heated benches make for a much more pleasant experience as do heated floors. This even if not doing a full Thermarium. The heat in the space does not sufficiently heat these.
Minimize Glass – Glass not only wastes energy but makes the steam bath less comfortable. Ideally limit glass to the door only or at most ≈1/4 of the total wall surface.
Also, all those photos of wonderful looking glass steam baths? Reality, even with a good squeegee after every use, is a 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. Primarily to remove exhaled CO2 to maintain a healthy and enjoyable environment but also to clear the humidity when we’re done to avoid mold and bacteria.
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 somewhat different from a sauna and also a bit trickier because we don’t have the convective loop to help us and we have various sources of heat to deal with. The locations of supply and exhaust vents, steam heads and bathers must all be carefully coordinated for the best experience. The good news is that it’s kind of difficult to create a really bad experience due to poor ventilation (I’ve only ever experienced one which was Ström in Quebec City). But good ventilation that results in fresh air and even steam is a bit more difficult but definitely worth the effort.
Mechanical Downdraft should generally work well for most steam baths so for this follow the guidelines for Mechanical Downdraft for Electrically Heated Saunas (in the menu above).
Fresh Air Supply Option 1 – In the ceiling.
Fresh Air Supply Option 2 – On the door wall about 6” below the ceiling. This should always include an updraft duct.
Distributed fresh air supplies often work better so rather than a single 6” supply vent for instance, eight 2” vents will cause less disruption of the steam.
Mechanical Exhaust – About 8” above the floor and far from the steam supply (head) and fresh air supply.
Post Bath Ventilation – Make sure to run mechanical ventilation for some period after use to clear out moisture.
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. Also not the ducting should not be any kind of material that will rust.
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 require routine maintenance so should be easily accessible.
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.
Note that storage tanks don’t usually work well unless pressurized separately.
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. My understanding is that this certainly helps but does not replace routine manual cleaning.
Manufacturers/Brands – Kohler, Delta (formerly Steamist), and Klafs are good options. Mr Steam and Amerec may be good as well. Note that Klafs is now owned by Kohler. Steamist, Amerec, Delta and Brizo are owned by Masco Corp.
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.
Construction
Steam rooms require a continuous waterproof membrane with a water vapor permeance rating of 0.5 perms or less be utilized. This is usually installed over the backer board and mortar bed.
Insure that tiles are rated for use in a steam room. Most should be fine but some are not.
The TCNA Handbook has additional information on proper construction.