stoveguy2esw said:
heating that stone is like heating from an unfinished basement. lots of "thermal mass" if the indoors is not insulated against the stone its gonna take a lot of energy to heat up that stone. however once it gets there its not as hard in most cases to hold it there. im with the gang on this , go bigger at least by an added 30-50% in rated heating capacity if uninsulated or not well insulated. the cool walls suck up heat until they are warm enough to start "refusing" heat at which point the house would start warming quite well, takes a little time to achaieve this but its definately doable
Why is that? According to the foundation specialists I've spoken to, most of the heat loss from a basement comes from the portion that is above grade. Yes, the OPs walls are entirely above grade, but they are also 40" thick.
The K-value of limestone is about 30 times higher than fiberglass insulation, but it acts as an insulator nonetheless. 40" of limestone is equivalent to about 1 1/3" of glass insulation. Once you have pumped as much heat into the walls as they will hold given the heat capacity of limestone (close to solid concrete) and the temperature differential between inside and outside temps, heat will continue to conduct through the walls like they had 1 1/3" of glass in place. But the the convective losses through the limestone walls will be basically zero compared to a conventionally built wall because they will be virtually airtight. Studies using sensors on the outside of above-grade walls have shown that an ICF wall of R-22 outperforms conventionally built walls of twice the R-value because convective losses through the walls are eliminated with the ICF.
Given all that, I agree with Backwoods that a stove that is rated for 1200-1600 sq.ft. should be adequate for this home. After several days, the OP should experience very stable temps because of the thermal inertia created by all that mass, but with a steady state heat loss equivalent to 1 1/3" of fiberglass. In his climate, that may be all that is needed.