At the suggestion of a comment from the last post, and to gather some data for what kind of performance might be obtained from a small purpose-built sauna, I tried sealing a 1,500 W forced-air space heater in our smallest bathroom (175 cu. ft., including the shower) for 15 minutes. Of course, I left the data logger in there, too.The results were as I expected: it made a toasty warm room– heating the temp by 20º– but did not show much potential for reaching actual sauna temperatures of 120+º. Not that this would’ve been safe, anyway, with a plastic space heater and tubes of toothpaste that would probably explode at the seams with such heat.
But, this situation had many things working against it. The heat capacity of the room is much too high (especially all that ceramic and water in the toilet tank), the walls aren’t insulated, there’s a window to outside, the heater was about 1/2 the power of even a tiny true sauna heater, and, most importantly, the whole room is about 75% too big. Address all those problems and I think I could have my goal: 150º in 15 minutes. Or under.