Hello all. I want to start burning wood in an outside boiler. I live on a farm in SE iowa and have plenty of "waste" wood right out my back door. I rent a farm also and spend a great deal of time "clearing" trees with the older farmer who ends up burning/wasting 90% of that in an un-insulated shop for his cats. Anyway, Central boilers are by far the most numerous in our area. I have friends who have them and absolutely love them. When I talk to the dealer though they always want to sell me the next to the biggest boiler. When I do the calculations though, I always end up with one size smaller (actually considerably smaller according to my calcs). If I compare my current actual NG (yes NG on a farm, lucky I guess) use I also confirm only the need for a much smaller unit. Admittedly, I want to start heating my garage and at some time will heat my basement. Right now though, my basement is at 67 degrees due to the type of heat and house that I have (see below). I built a 2 story insulated concrete form home with complete brick siding. I have ~R40-50 in the ceiling. I heat the house with in-floor radiant heat throughout the entire house excluding the garage (tho it has the hot water tubes in the slab). Above grade we have ~2850 sf plus ~1700sf below grade. I have 11 heat "zones" and shut off all the basement zones because the heat actually goes down too and so heats the basement to 67 degrees because there is no insulation/drywall up on the ceiling yet. Sorry so long. Anyway, I'm having difficulty swallowing that I need a 500,000 btu boiler when on the worst winter months I only use 180+/- terms. They tell me it will allow longer burn times because more water heated etc, but then won't it also require more wood/be less efficient? Any comments are welcome.