In Finnish sauna culture, löyly refers to the heat-and-humidity wave created when water is thrown onto hot stones. It is the part of the sauna you actually feel — and good löyly depends on the whole room working together.
Finnish design guidance commonly places the upper bench about 100–120 cm (39–47 in) below the ceiling. That keeps bathers up in the warm zone instead of sitting in the cooler lower part of the room.
A traditional Finnish design rule says the foot bench should ideally sit above the top of the heater stones. It is a practical way to reduce cold feet and keep more of the body inside the warm, humid löyly zone. It is a guideline rather than a substitute for proper heater and ventilation design.
Fresh air supports comfort, combustion where applicable, circulation and drying. Vent locations change depending on the heater and whether ventilation is natural or mechanical, so vents should be designed as part of the heater system rather than added at the end.
Harvia’s electric-sauna guidance calls for roughly six air changes per hour. With mechanical ventilation, supply air is typically introduced higher in the room; with gravity ventilation, supply air is commonly placed below or beside the heater and exhaust low and away from it.
The heater’s power and stone capacity affect how the sauna responds when water hits the stones. More stone mass can provide a softer, longer release of heat, while the correct heater size still has to match the room volume and construction.
Glass and other uninsulated surfaces lose heat faster than insulated walls. Harvia’s sizing guidance treats each square metre of glass or similar uninsulated surface as roughly 1.2 additional cubic metres of effective sauna volume when selecting heater power.
The cedar is the finish; the wall assembly behind it controls heat and moisture. Insulation reduces heat loss, while a properly detailed sauna-rated reflective vapour layer helps manage moisture and reflects radiant heat back toward the room. Details around penetrations, windows and doors matter.
Cedar performs well in hot, humid spaces, has relatively low thermal conductivity, is naturally durable, and brings a warm grain and distinct aroma to the room. It is not the only good sauna wood, but in Northern BC it also gives the build a strong sense of place.
Neither one is automatically “better.” The right choice depends on the location, room, power availability, ritual you want, and how hands-on you want the heating process to be.
