Heating with wood is "greener" than heating with electricity produced by burning fossil fuels.  I just became aware of "masonry heaters".  These are what might be called super fireplaces.  They burn relatively small amounts of wood very hot, fast and completely and store the heat in lots of masonry which keeps giving out stored heat long after the fire is out (24 hours or more).  They typically are only burned once or at most twice a day & the fires last an hour or two.  They usually have  a long path for the burned gasses so most of the heat is captured & stored and the gases are really cooled (300 degrees is not unusual). Many have bake ovens that'll heat to 500 deg f and stay above 350 for several hours They are a good match to a well insulated and sealed house.  I sure would like to hear from users.

This guy is one of the most respected masonry stove builders in North America. He has built stoves for at least 30 years and a few on houses that I have worked on.

http://heatkit.com/

You'll find some masonry heater owners at hearth.com. Also, builditsolar.com has links to numerous diyers, many of whom are quite approachable. If you can locate a masonry heater in a place where it will pick up passive solar during the day, you can get double duty from it.

I passed on a masonry heater because it chewed up too much floor space in my 1600 sf house. Instead, I have an indoor wood stove boiler to heat a 200 gallon heat storage tank, which in turn heats a radiant concrete slab. It's the same principle: one efficient, full-bore burn a day; heat for 24 hours. Plus thermostats. Feel free to skip the storage tank and heat the slab directly but make sure to err on the side of too little stove rather than too much . These people sell storage tanks and controllers to integrate wood, solar and fossil fuel/electric: http://www.stsscollc.com/solar-water-tanks-and-heat-exchangers/

Take a look at http://www.mha-net.org/index.htm for ideas and contacts. There is also a Yahoo discussion group that is a great source of information: http://groups.yahoo.com/group/MasonryHeaters/ I do not yet own a masonry heater, but I have decided to include one in the ICF home that I am planning. I came upon masonry heaters while troubleshooting the poor efficiency of traditional fireplaces. These heaters burn hot and clean (no creosote), absorb a high percentage of that heat, and then slowly radiate that heat into the living space over 12+ hours. I am really amazed that they are not more popular.

My wife and I heated with a masonry stove for about 10 years. One concern we encountered is the potential to poison your self with carbon monoxide if you attempt to run the stove supper efficiently ie by closing the damper down too tight with a large coal bed. We set off our CO detector more than once and I'm certain we suffered at least a bit from low grade CO poisoning. I'm sure many of the more modern systems have dampers that can not be closed tight but those will be blowing a good deal of heat up the chimney.

We're now heating via radiant floor using a super efficient natural gas condensing boiler and really love it.

Contact me if you'd like to discuss this more.

Hugh

One of the core concepts of a masonry heater is to burn a very hot, fast fire and let the 1-2 tons of masonry absorb that heat so that it does not "go up the chimney." This is accomplished with a long, complex flue run that provides enough surface area to absorb 90% of the heat before reaching the chimney. As far as I know, they are designed to be run only with the damper wide-open. A properly-sized and operated masonry heater will inherently be super efficient, and so closing the damper while in use would be useless and dangerous.

2 weeks ago I was involved with a church missionary team that built 20 efficient stoves in 5 days to the village of El Pariaso, El Paraiso, Honduras
wood is the primary source for cooking
cost of materials are about $100. USD each



Commonly known as "Rocket Stove Design" , they are 70% efficient, smoke was eliminated from the households, providing a huge health and economic impact to the families that received them

Posted By OnWisco on 08 Jul 2012 01:49 PM
One of the core concepts of a masonry heater is to burn a very hot, fast fire and let the 1-2 tons of masonry absorb that heat so that it does not "go up the chimney." This is accomplished with a long, complex flue run that provides enough surface area to absorb 90% of the heat before reaching the chimney. As far as I know, they are designed to be run only with the damper wide-open. A properly-sized and operated masonry heater will inherently be super efficient, and so closing the damper while in use would be useless and dangerous.

How many years have you used one? If you run the unit with the damper wide open until all embers are completely consumed I guarantee you will chase a good bit of your heat up the chimney.

Hugh

SciGuy;
Not true the stoves we constructed had heat directed thru a combustion chamber under a 24 x 36" Plancha, smoke was directed thru a simple chamber to a 4" uninsulated galvanized pipe (no damper) The temperature at the front of the plancha was 450 deg. gradually reduced to 200 towards the chimney and the 4" pipe itself was cool enough that you could put your hand on it momentarily, about 130 degrees

You'd want an outisde air supply for any wood burning appliance in a modern, tight house. According to the Mo. DNR, this stove is 90 percent efficient with outside air and extensive baffling to capture heat in the exhaust. http://www.dnr.mo.gov/pubs/pub781.pdf A modern wood stove is 70 percent efficient.

If you run the unit with the damper wide open until all embers are completely consumed I guarantee you will chase a good bit of your heat up the chimney.

That's the whole point with wood burning masonry heaters. They are designed so as not to lose that heat just as cmkavala and toddm say. The theoretical maximum heat transfer efficiency with burning wood is right up there at 85% without complex condensing flues. Masonry heaters have been shown to hit 80%

You may be thinking about your average fireplace, which is ludicrously wasteful and inefficient, both in burn efficiency and in heat transfer.

This is exactly the way the best wood boilers work (or any solid fuel burner for that matter). A hot clean burn with storage.

The reason masonry heater are not more popular is the cost of installation and the obvious limitations of control (both burning and output). The CO concern is real, as my little Morso will always produce CO in the 5000ppm range every time I fire it up. Only in the best and hottest condition with dry oak, will it produce an acceptable level of CO. The unit is fire lined, rated at 75% efficient, properly vented has plenty of combustion air (I am a mechanical contractor).

These are the limitations of solid fuel burners.

My specialty is hydronics, so condensing boilers 96% thermal efficiency (very green), gasification outdoor boilers 80% combustion efficiency (also green) and electric boilers for backup are my stock-in-trade. Less work, more control.

Now, if you are in the third world, we are in on a different subject.

A cold stove will burn inefficiently until it develops a strong draft. At that point CO should no longer be an issue in a proper design even as the fire dies to embers. With an outside air supply there is no reason to close the damper because the stove is not drawing conditioned air from the house. One suspects that draft is a bigger issue with masonry stoves because of the mass in the flue. But no problemo if you have lots of kindling and pile it on the initial minutes, While this could be a recipe for a chimney fire in sporadic use, masonry stoves lthat are always lit this way, fired with dry wood and burned without dampening should have very little soot buildup. I'm not sure how you'd clean a masonry stove flue so closing dampers would be a no-no in my book.

FWIW http://www.mha-net.org/docs/Manual-heater.PDF
There is a clear warning DON"T CLOSE THE AIR INLET DAMPER TILL ALL FUEL IS BURNED!
Most of the designs I've looked at have both a combustion air control damper and a flue shut off damper. Other than seasonal complete shut down I see no reason to ever close the chimney damper, as the combustion damper & airtight construction (hopefully) of the heater prevent any lost heat due to chimney draft. Some also have a 'bypass' damper control that shortens the flue, eliminating much of the heat exchange passages, for easier cold starting. The bypass should, obviously, be closed once the fire is started.

I like the idea of a wood burning boiler and a several thousand gallon water storage tank much better.

I always liked you Jonr :-).

For readers who might not know that jonr is exaggerating to make his point: raising 2000 gallons of water by 50 degrees would require 1,000 pounds of oak firewood, or 1,500 pounds of poplar or pine. A chore performed weekly will tend to be seven times harder than the same chore performed daily.

I have two rules for wood heat. It should be the last resort. If you find a masonry heater, you have probably found a passive solar house as well. When you need it, it should be right there in the living room with you as a baleful reminder of your attachment to the sofa.

OK, no more math before that first cup of coffee. Raising 2000 gallons of water by 50 degrees would require 800,000 btus. With oak at 6k-7k btu/pound, a 70 percent efficient boiler would get there with 160 to 200 pounds of wood, or half again as much for softer woods like pine or poplar. But 800k btu is slightly less than 5k btu/hr over a week, not counting storage losses, so you still might get to 1000 lbs/wk in a very cold climate.

I'm really not exaggerating. Several thousand gallons allows less frequent fires and low water temperature. Low water temperature allows greater boiler efficiency and the use of plastic tanks. 2000 gallons is 400K btus at +25F. About right to get through a cold night (depending on your house and the climate). About $1000 for the tank. Perfectly controllable comfort.

About $1000 for the tank.

What kind are you thinking about?