I have seen several “designs” for ventilation of saunas with electric heaters but no so much for wood fired saunas. Some have show exhaust ventilation under the upper bench with fresh air coming in on the wall under the electric heater or by having a space under the entrance door. I have seen other designs with the exhaust vent in the wall above the upper bench.
So with a wood stove I’ll need combustion air and wondering if fresh outside air should be ducted to under the wood stove. If the fresh air comes in from under the door to the chill room I’m wondering if the chill room will get too cold pulling in 10 below zero outside air.
For exhaust air from the hot room, what type of duct is commonly used? I’m thinking standard metal duct will rust from the humidity, Not sure is something like PVC pipe, say 4 inch is large enough.