I have seen several indoor wood boilers for free on craigslist and this has got me thinking. I would like to build a sauna and my original plan was to find a used wood furnace, take off the sheet metal housing on the outside and weld up baskets to hold the rocks. If i used a wood boiler I could possibly heat a hot tub with heat exchanger as well. I am wondering how hot the sides and front of a indoor wood boiler get? I am guessing they have the water jacket on the sides and top of the firebox, some insulation, and then sheet metal. If I removed the sheet metal and insulation do you think it would be hot enough to use as a sauna. Thanks for any input.