I've tinkered with a couple of rocket stoves just messing around but I'm getting more interested in mass stoves since our house seems to stay cold all winter and we refuse to turn up the thermostat. The house is well insulated but we have 18 feet of windows on the front of the house and the wind blows here most every day.
We have a fireplace but they are so inefficient that we don't use it. We also live on the treeless plains of the Texas panhandle. The mass stove has me intrigued. I can see where we could get a good fire going on the weekend and used the stored heat during the week. A mass stove would also allow use to minimize how much wood we would need to store.
I do have a couple of questions:
1) My wife is not going to be very thrilled with a 30-55 gallon barrel sitting in her living room. How are some ways to hide, disguise, or otherwise dress up a barrel?
2) I anticipate tearing out our old fireplace (an inset) and using the existing chimney for the exhaust. Is there a height or length limit on it or the duct work?
3) What types of fire safety should I be concerned with? It seems a mass stove will be much safer than a fireplace but I hesitate leaving a fire unattended.
1) The barrel can be dressed up or disguised in a number of ways; there is a thread here on that topic. It is even possible to substitute a masonry bell for the barrel, which will change the characteristics of operation somewhat. If you have masonry surrounding your existing insert, that would be a good backdrop and possibly part of the mass depending on details of your layout.
2) A good chimney is an asset, and there is no real limit on its height aside from throttling a very tall one if the draft is too strong. There are standard lengths of horizontal ducting in the mass, depending on the diameter of your system and the number of elbows. The book Rocket Mass Heaters by Evans and Jackson has most of the information you will need to adapt to any location.
3) With the length of heat exchange ducting, the low final exit temperatures and the initial complete combustion, you should have no exterior fire concerns, and the standard J-tube design has the wood feed such that it is very hard for fire, burning wood or sparks to fall out. A J-tube needs to be fed on a regular basis so you cannot go away and leave it for a long time. For even more safety, you can use a batch box design, which has a closed firebox, loaded once and burning steadily for an hour.
Thanks for the info and links. I do think a batchbox mass heater would serve my purposes better.
Those are some pretty designs. I suspect mine will be less artistic.
A little more about us. Both my wife and I work away from home. It would be nice to have a wood fed heater that could either be left burning with minimal fear of it getting out and burning down the house or a mass heater that would hold heat. It seems a batch box would be the ideal combination of both. Even if it is something we load and light when we get home at night we could let it burn down through the evening and use the heat overnight and into the next day.
I'm not probably going to get totally away from using our conventional LP HVAC but I'd like to be able to supplement it as much as possible.
I have access to all the pallet wood I can haul off at work so that helps on the fodder.
As mentioned by Satamax maybe our house is not that insulated compared to some of the houses y'all might live in but for a pier and beam brick veneered stick house it's loaded with insulation. It is well insulated for our part of the country. It is the windows that really hurt us. I am also pursuing solar heating options but the mass heater seemed to be the best return on the money to begin with. My solar heating is going to be a bigger project with a greenhouse addition to the side of the house. A mass heater should be much less expensive and be productive on days like we are having, 15 degrees, wind, and no sun. There may also be a little desire to tear out our old ugly fireplace and replace it with something more efficient and certainly better looking.
I am having difficulties finding any good, or should I say concise, information about Batch Box heaters. Does Evans and Jackson's book have information about Batch Box mass heaters? It sounds like a good book. Give me a good plan, or even the ratios and I'm confident I can build it.
Location: Southern alps, on the French side of the french /italian border 5000ft elevation