Question: We have been looking for a woodburning central unit that goes outside the house. We have the duct work in the house now and we are looking for one that does not use water. I have seen them in the past but I don't know where to find them now. We also have 80 acres of wooded land and a lot of dead wood out there just going to waste. Answer: Outdoor air units are quite inefficient, as air is not a good conductor or storage medium for heat. There are very few units of this type, however, I thin US STOVE CO (Pittsburg, Tn) , under their Clayton label, makes one. It might be better to use a hot water unit, and use a duct-mounted heat exchanger to change the heat to hot air. Also, consider putting a boiler in a garage or outbuilding so you do not have to brave the weather to load it. In addition, there will be less heat loss.