I recently finished reading “Finnish Sauna” by Allan Konya. He pointed out: “The sauna is the only form of bath in which both dry and damp air are present, and in which the dampness can be controlled by the bathers themselves.” (5) “Some people consider that the pile of stones on top of the sauna stove is a relic of an altar used in pagan times and that the throwing of water over the stones was a form of sacrificial ceremony to supernatural beings.” (7) I think this is more than a bit of a stretch, but a fun piece of lore all the same. “On entering the hot room, bathers are enveloped at once by a delightful heat, not stifling, in no way oppressive, but rather like the protective, nurturing warmth of an incubator.” (13) I like the analogy of a sauna to an incubator. “It is advisable to start off with a lower temperature and increase it gradually to the required level. This allows one's blood vessels to expand slowly and the circulation to improve.” (14) Especially for the novice! “Sauna and an after-sauna supper (saunapala) is a fairly common form of entertaining.” (16)
“Too low a humidity can result in the following problems: an unpleasant 'dry room' smell; the drying out of the mucous membranes of nose and throat; perspiration evaporating too quickly from the skin surface, allowing it to become too dry.” (18) “Fresh air should ideally be drawn directly from outside and certainly not from an adjoining room where odors may be present... The correct (and traditional) position for the [venting] outlet is in the wall opposite the inlet and at least slightly above it.” (19) An outlet area of five square inches per person is recommended. Later on page 74 he begins describing how a flue above this outlet can improve the suction and form the updraft needed to counteract any effects of back pressure. An illustration of a venting outlet flue inside the sauna is shown, although I might consider putting this flue outside the wall, where it won't take up any interior space. Konya describes something called the “piston effect”: “When water is poured on the stones, the superheated vapor expands greatly, rising quickly to the ceiling and forming a thickening blanket of loyly which pushes the air downward, forcing the heavier stale air through the outlet. This phenomenon is sometimes referred to as the 'piston effect', a term which describes the action rather well.” (19)
On construction: “The roof usually projected over the gable end which contained the low door – not much above chin level and with a high threshold.” (9) Konya recommends siting the sauna such that the windows face west “as the time for to sauna is generally the evening, very often at sunset, the rays of the setting sun will stream into these rooms, helping the bathers to relax.” (31) “Once the [sauna] room approaches a square on plan, arrangements with L-shaped benches are usually more economical, up to a size of about [7x7 feet] internally.” (33) Regarding floor construction “Materials like linoleum, which have a characteristic smell, must be avoided at all costs.” (48) “Benches supported only from the walls... it is better to avoid timber supports at floor level, where fungal attack is most likely to occur. [But] wherever the benches are supported on the floor [and stabilized with connection to the walls], rubber doorstops should be screwed to the undersides of the supports with non-ferrous screws, to prevent contact between the floor and the end grain of the timber.” (52) “Cellular plastics... some types cannot withstand the high temperatures encountered in a sauna.” (61) I should call the manufacturer to see if foil faced R-max foam board insulation will work in this application. “The door... can consist of a standard solid core flush panel door, with insulating material, vapor barrier and paneling added to the inside face. A heavy ball or roller catch keeps the door closed. If it must be locked... a hasp and staple with padlock offers the best solution.” (73) “To ensure sufficient draught for effective operation, the flue should, if at all possible, be not less than about 13 feet in total length.” (88) A gable roof, rather than a flat roof, would support a ceiling peak of greatest height for a tall chimney flue. “The [chimney pipe] joints must be airtight and should be fitted with female end upward otherwise there can be difficulty with tar and condensation leaking to the outside of the pipes...” (89)
I also enjoyed looking at "Finnish Villas and Saunas", which is a feast for the eyes.
Aristotle said: "We educate ourselves so that we can make a noble use of our leisure." The idea that education is for the mind and soul, for the whole person – the citizen, the parent, the voter, the reader, the lover, the traveller, the human being in the round – is lost to view in trying to make university education a mere continuation of school for the same sausage-machine purpose of churning out employees. - AC Grayling