I just got back from the Northeastern Forest Products Equipment Expo in Essex Jct., (Burlington) Vermont, where I saw an interesting boiler design. I have the lit at home and will dig it up and give you all some details, but it's basically a 120,000 btu/hr boiler that looks like a glass-front wood stove. In fact, it's designed to be installed in living space. It doesn't have much water storage to speak of at all--just a bunch of tubing around the firebox and at the bottom. Takes an 8-inch chimney and has a huge glass loading door. The Swedish guy selling it said that you would need water storage, but that a standard 50-gallon water heater would work well. It had a half-inch tapping for the water return and what looked like a 3/4-inch supply tap(!). Natural draft by way of a bimetal draft regulator. Interesting rig. Looked like your typical weird-but-effective European design. My guess is that if it works at all, it would work best with a high-temp/low water setup like baseboards. I have trouble believing this thing, which sells for about $4,000, can crank out 120,000 btus per hour, but that's what it's rated at. Anybody know what I'm talking about?