How We Build
Heat
Heat doesn't come from the stove alone — it comes from the stones on top of it. Electric and wood-fired heaters both work by superheating a bed of stones, which store and radiate heat evenly. Undersized stone beds are why cheap heaters run hot and dry instead of steady.
Löyly
Löyly is the steam that comes off the stones when water hits them — a spike of heat you feel on your skin, not just added humidity. Small amounts of water, added slowly, with time to recover between throws. Too much too fast just scalds.
Ventilation
The part most kit builds get wrong. Air needs to enter low, near the stove, and exit high on the opposite wall — not stacked on one side. Get this backwards and the room won't heat evenly or clear between sessions.
Wood
Interior wood has to stay cool enough to sit on and touch at head height, which rules out anything dense or resinous. Species like aspen and cedar are chosen because they don't retain heat and don't off-gas — not for how they look.
Bench Height
Heat rises, so a few inches changes how a bench actually feels. Standard practice is two tiers — lower for a milder session, upper near head height for full heat. Get the dimension wrong and one tier stops working for most people.
Space
Indoor or outdoor, the room has to be sized to the heater. Too large and it runs cold and expensive to heat; too small and the temperature gradient between floor and top bench never develops.
We're not reinventing anything. We're just paying attention to what works.