In our ongoing effort to get further off-grid/self reliant we have started looking into wood furnaces and boilers. The house is 2 story with a full basement, 2 forced air systems (one feeds basement and 1st, the other feeds the second floor), and a boiler that feeds the basement and main level floors. The house is an ICF house (insulated concrete forms), and has an incredible R-value (walls from footing to the roof are continuous R28, windows are triple pain, attic is R60), I've run it through hvac calc at work and the heating requirements are extremely low- coming in at 36K btu. In fact when the furnaces do come on they stay in low fire and cycle off, even in the sub-zero temps we had last week (they are small 60K btu furnaces putting out 28K in low fire) while keeping the house at 70. This leads me to believe my wood consumption would be pretty low. I'm open to either because I've found model furnaces that have provisions to heat water as well (I'm all about redundancy), but would like to know if anyone has a brand or model they really like. We screwed up a little during construction and had planned on a direct vent natural gas fireplace, but I scratched that idea once I realized you can't burn wood in them. The first salesman we talked to said we could but I followed up with the manufacture (Lennox) and fould out he was wrong. Without gas, it's useless. Unfortunately, this was thought of too late and we didn't have a proper chimney installed when the walls were open. We already have plans and approval to build a chimney on the exterior of the house that would be framed in and insulated to maintain a proper draft, just need to be sure of what model we run with so we size the chimney pipe properly (or we can err on the side of caution and run 10" as most I've seen require 6 or 8").
Have you considered an outdoor burner? Use water/antifreeze to move the heat into coils in the air handlers. One of many - Central Boiler - Outdoor Wood Furnace for Home Heating As it happens, there are quite a few of these specific burners in my AO.
I was going to ask about these, but read in a few places they are very inefficient because of heat losses from being outside. With proper insulation this would be negated. A unit like this would probably have substantially lower installation costs. Thanks, I'll start looking into them! My other reason for looking into the indoor ones is opsec related- I like the concept of "out of sight out of mind".
Have two friends who built their own outdoor furnaces. They used a small tank inside a slightly larger one and super insulated it and the lines going into the exchanger. Built my hot air wood furnace many years ago for out two story. Putting it back into service this year by placing it on the rear covered patio and ducting it into the basement's duct system.
