This fall, I built an outdoor wood/coal furnace using a US Stove 1557. I built a shell around the stove to keep the weather off of it, and to insulate and prevent heat loss. The best part is there is no mess inside my home. On a cold day (high temps around 20f) I fill it 3 times/day. I usually burn coal with the wood when it’s that cold. At night I fill it around 9pm, and we stay warm all night. At 7am there are still hot coals in the stove (when I burn coal, wood has coals but not as much).
The stove was framed with 2X4 metal studs, insulated with R-13 fierglass insulation, and covered with scrap metal from an old barn. This is a forced air furnace. The air is being forced into my existing HVAC ductwork and spread throughout my entire house. I created a return vent that runs direct to the stove. I still have the ability to use my heat pump, and use a damper to prevent air from circulating back out to the furnace when there is no fire outside.
I have burned a mix of wood and coal this winter, and the savings on my electrical bill have been great. We have had a mild winter, but even so, the savings have been amazing. This video is for demonstration of the stove only.