To add to Oblio's post about woodstoves: You really need to have an open floor plan to make the best use of a woodstove or fireplace insert. Even better if your house has a lot of thermal mass, that can hold heat while the woodstove is running and then release heat when you go to bed.
Our woodstove is in the center of a very old timber-framed house. The chimney stack is a real monster of a creation, a combination of granite and brick, and it holds heat like a champ. But, the floor plan is very old-fashioned, designed to shut certain rooms off completely in the winter for heating efficiency as well as for privacy. You can get heat-activated fans to blow the hot air around that sit on top of the stove, but despite all that our brand-new Vermont Castings stove only heats maybe 2 1/2 rooms and a hallway up to a comfortable temperature. In the dead of winter, frost forms on the inside of windows at night, in the rooms furthest from the stove.
Also, they run best on hardwood. When I bought this place, the wood shed was stacked full of about 2 cords of firewood. I thought, yippee! No need to cut or buy firewood for a winter or two! Yeah, uh, it was almost all pine. I can stuff my woodstove full to the top, turn the air vent down to barely-open, and all that pine will be nothing but ash in about two hours. In comparison, two hickory, locust and maple logs will last more like 4-8 hours. Believe me, it really sucks to wake up at 2am freezing your butt off because the woodstove that you crammed full to the top at 10pm is ice-cold.
And, as one of my engineer friends was very disappointed to find out, the house won't smell like a wood fire at all while a super-efficient woodstove is running. So if you're addicted to that nice smoky smell, you're outta luck.
