With slipstone, the interior is not stone, but concrete. Our house (c 1920s) was a carriage house, with a sheetrock interior added much later, without adequate space between the two for enough insulation (although there is now hard foam that takes up much less room than the equivalent r-value of blankets). The exposed stone inside are the massive fireplaces and occasional bits of wall. You want to heat with wood, but you do know that a fireplace does not add warmth, only ambience, right? (Which is not to disparage that ambience in the least!) To heat with wood, get an expert to design a good system that will let you stoke your fire in a stove (outside or inside) and distribute it through the house in baseboards. Figure out what your source of wood will be, and how it can be convenient for this operation. This could be the cheapest and most convenient way for you to go. We do live in our house full time, but making any house as energy efficient as possible buys you such peace of mind. Taxes and interest rates you can't do much to control - but energy consumption you can. And it will affect how you use the place. If it's cozy in late fall and winter and you USE it without worrying about draining pipes and shutting it down -- that's worth quite a lot.