Masonry heaters are awsome. I actually studied these in college, many years ago. We were building them and conducting efficiency tests on different designs. Back then we called them Russian fireplaces, masonry stoves, and a few other names.
We found a few designs to be over 90% efficient - meaning that for every 1000 btu's of wood used in it - 900+ btu's of heat into the living space. A few were about 94% efficient and a house could be heated with just an armload of wood per night.
By the way - I know of no-one these days who is qualified to build a masonry heater properly. Proper design and construction are an absolute requirement to get it right.
I have 2 wood stoves and this is my primary heat source. I would like to build a masonry stove someday for my home similar to those we studied in school.
A traditional fireplace can be as much as 95% inefficient - with alomost all the heat going straight up the flu. The only thing worse than that - is a Fake fireplace - operated with gas.
I consider those units to be the "yuppie special" - especially fit for a McMansion owner with more money than brains, complete with a remote control to turn the fire on and off with.
If you have a fireplace - a wood insert will improve the ability to use it for heating the home. Fireplace inserts are essentially a wood stove placed into a fireplace space. Many wood stoves and fireplace inserts are 70+% efficient these days.
A pellet stove is a way to heat with wood too - except that you have to buy the pellets, and most of those stoves need power to run them.
I like the good ol' fashioned wood stove. The fuel grows all around us. Many of us don't pay much money for the wood, because we cut it ourselves. I like cutting and splitting the wood, but it's not for everybody.
I would not recommend this for Mr. Yuppie Mc Mansion owner - stick to your remote control fireplace.
I get excercise cutting wood - not in a gym but outdoors in the hills - and I pay my heating bill at the same time.
P.S. Somewhere I have all the literature I collected in college - I can't find it but someday I'll go through all my boxes of stuff. For anyone who might be interested in maybe educating some mason's in our area about these awsome fireplaces - I have dug up some information about them. It would be nice to see this technology used more in our area.
This PDF is similar to the designs I saw in the late 70's and early 80's. It will give some idea's of how to build a masonry stove correctly.
http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBMQFjAA&url=http%3A%2F%2Fwww.dnr.mo.gov%2Fpubs%2Fpub781.pdf&rct=j&q=missouri%20masonry%20stove%20pdf&ei=f8j3TL-TBoa8lQe9zY2OAg&usg=AFQjCNGpHkQ0O3bBFCJ65cD7tem5Hrzpew