I have a small nuway stove for my 4x6 portable, and I built a bigger version of it for my 8x9 permenant shack. Its 18x18x26 and heats the perm shack great. Couple big logs will keep it going for about 4hrs and the temp in the 80's or higher depending on how much I stoke it. I've also built quit a few small wood burners out of old 20lb proprane tanks, just make sure that all the propane is out and I fill them with water then cut out the holes with a cut off wheel.