Outdoor wood boilers are banned in many areas because many of them are very inefficient, and pollution/smoke is a problem. People also burn all sorts of garbage in them since they're outdoors.

Most outdoor wood boilers don't come close to the efficiency or longevity the Dectra Garn units.

I have to laugh when I see all the displays at fairs, and sales/installation outfits advertising free heat as a marketing strategy. The installed prices of the highly efficient outdoor wood boilers, and highly efficient wood gasification boilers are quite high.

If I were concerned about using renewable energy, I'd be looking at a wood gasification wood boiler, or a pellet boiler. The europeans have some wood, multi-fuel and pellet burning equipment that make some of our hillbilly engineered systems look like toys.

Here is a link that might be useful: Garn Wood Boiler

I'm not 100% sure, but my guess is that Burn2788 is selling those furnaces. Perhaps that's why he dredged up a bunch of old, dead threads (some of them were last active over a year ago), and posted links to his website on them.