Can I Build Onto This Stove Somehow?

Hi all,

I have one of these: Military Wood Stove

I am currently living with my daughter in a 7'x20' room in our barn while we work on building something else. The walls are concrete block. When we moved down here, I found myself with very little cash and winter fast approaching, so I bought that stove. All in all, it's been a good little stove, and once I figured out its quirks it's worked well. It's just too small to keep up with heating that room once the temps get much below 35* or so.

I've got a bit of cash now, and I want to do something so that we can be more comfortable in cold weather. I could just buy a bigger stove, but that would pretty much take all of what I currently have available, and I'm sure y'all can understand that I'd like to stretch the money as far as possible. So I'm wondering if I might be able to do something with this little stove to oomph it up a bit.

I've heard of people building a fire brick box around their wood stove to hold and disperse more heat. Would that work here? How big could I make it before I'd lose any heat advantage?

If it's a stupid idea, just say so ... I don't dwell in The Land of the Perpetually Offended, and I'd rather have people tell me straight up.

(And yes, I do want a RMH heater eventually, but I have more urgent projects, so I just want to do something quickly for now.)

I don't feel qualified to give you too much input on modifying this stove, but I'm very curious what feedback you'll get.  It may be relevant to know if you have any fabrication tools/experience.  Like a welder, grinder, metal cutting tools, etc.
For my part, I had a very similar situation (same size space, with a temporary heating need) and I took the easy way out and bought a beat up, used, inefficient, cast iron stove for $55 - and it got me through my 2 year gap until I was ready for my permanent solution.  Not as fun, but it worked.  Probably could have sold it for what I paid, but gave it to a relative.  Depends on available time I suppose.

Good point, Chris ... I don't have any experience in any of those things, so if I needed to have something welded, etc., I'd have to pay to have it done.

I have been scouring Craigslist and anywhere else near me that sells this kind of stuff used. The pickings are slim. So far the only used stoves I've come across are way bigger than what I need and still cost $400. I can't seem to find any small stoves for sale. Maybe once the heating season dies down there will be some available.

Building thermal mass around your woodstove does retain heat in the room. It works best when the stove is touching the mass, but it still helps when there is an airgap. My parent's house has a large brick structure around, but not touching, their stove. After seven or eight hours of hot burn, you can walk behind the structure and the bricks are warm to the touch.

Our shop has a typical woodstove. I stacked some red bricks on the flat top of the stove against the stove pipe to soak up some heat and radiate it back. I haven't measured it, but it feels like the shop stays warmer for a longer amount of time now.

It looks like the back of your stove is the flattest part. If you think the temperatures are not too high, you could back the stove up until it touches your concrete block wall. This would be a decent test of it's heat transfer into masonry.

Good idea, Jeremy ... thank you! I'll back the stove up against the wall when I get back home and see what happens.

One way I was thinking of building around it was to take the legs off the stove and set it right on the fire brick. That would take out the air gap and make the whole thing a bit more stable, at least in the picture in my head. I also wouldn't mind having the door up a bit higher.

Is there a huge advantage to mortaring the brick vs. dry stacking it? We won't be living in that room forever, so at some point I'll probably want to move this thing.

You say the walls in your barn room are concrete block - that is a very efficient heat sink all around your living space with the other side exposed to outside temperatures. No matter how big a stove you get, you will never make those walls warm in cold weather, so even if the air temperature gets to a comfortable point, any place not in sight of the stove is going to be radiating to the cold walls.

I think the best bang for your buck will be to buy some insulation and put it on the walls. Depending on your conditions, styrofoam panels might be appropriate, or rolls of aluminized bubble insulation. $50 can get enough to make a section of wall feel warm behind you as you enjoy the stove. Whatever you get, you may be able to incorporate it into your future home so the material is not ultimately wasted. It will reduce your need for wood, or allow more comfort with the same wood.

Backing the stove up to a mass wall would be a good idea if the other side of the wall was warm, but heating your exterior walls will just be trying to heat the outdoors.

Insulation is definitely on the list. Maybe I'd be better off insulating first and then seeing how much more i need in the heat producing department.  Thanks!

At this point in the season, I would guess that insulation would make you comfortable enough until spring. Adding insulation as you can over the summer may well allow you to be warm enough next winter if you need to live in the room then, without altering your stove. I would certainly suggest piling rocks around it this summer, perhaps cobbed together, to give you some thermal flywheel so it doesn't get cold the minute the fire goes out. There will be some clearance you need for safety anyway, and filling some of that clearance with rock will not hurt anything. If you can make a flat top to the surround, you might even get a bit of counter next to the stove for cooking ease

Have you looked at the kits that turn a 55 gal drum into a stove?  Here you can buy a drum for $10, or get one free if you keep your eyes open, and you can buy the kit for $50-$75.  They really put out the heat, and at some point if you have a different situation, you can use it to heat a shop or something.

Thanks, Glenn. That's probably what I'll end up doing.

Todd, I have looked at those. With the lack of used wood stoves in my area, that's probably the route I'll go if I do end up replacing my stove. I just wanted to be able to use what I already have if possible.

Hi Ferne

First:  I hope that you burned off the paint before you brought that heater in your living space.  It's apparently pretty nasty stuff.
 

heard of people building a fire brick box around their wood stove to hold and disperse more heat. Would that work here? How big could I make it before I'd lose any heat advantage?

So, I think you do have a good idea here.  And since you are considering building a RMH at some point anyway, getting firebrick is not a bad idea (check your local buy and sell sort of sites or Habitat For Humanity and you might get a good price on the fire bricks).  You can do this with regular bricks, cinder blocks filled with rammed Earth, sand, cob... whatever is good and accessible and solid-ish mass, or as Glen suggests in the quote below, Rocks and cob when you can.

I would certainly suggest piling rocks around it this summer, perhaps cobbed together, to give you some thermal flywheel so it doesn't get cold the minute the fire goes out. There will be some clearance you need for safety anyway, and filling some of that clearance with rock will not hurt anything. If you can make a flat top to the surround, you might even get a bit of counter next to the stove for cooking ease

I would suggest building a "U" shape of some sort of material around the stove, giving yourself room between your stove and the mass so that it serves three purposes.  1.) It scoops the heat and throws it reflectively back at you,  2.) it absorbs some heat and radiates it later.  

and 3) The third purpose is that you get to inspect your cheap ass stove.  No offense, but such things are not meant to have sustained hot fires for months on end; the metal is too thin and is bound to fail, even if you keep it functioning well and never let it get wet/rust/corroded.  I don't know if that bad boy came with an instruction book, but if it did, read it and follow it.  You are bound to want to get the heat pumping with that unit as it's winter and you have a kid, but it is small, and that stove pipe that comes with it is barely adequate to handle the kind of rocket that that sort of design can put out so it will be demanding air.  Check that pipe often for damage, and cleanliness.  Only burn dry wood.  Never close your door air damper fully stopped as these stoves will build up gas (because of the narrow chimney not allowing up and down drafts at the same time), and end up exploding on you when you do open it, giving it an air supply.   Go on line and check for product review videos. Watch them.  I guarantee you will see on them and make note that it will not be long before you notice... after a while that the inner grate will fail; it will simply have had too much heat, while holding heavy hardwood shifting under flame.  If a large hardwood log is leaning against the side of a cheap thin walled stove, and becomes a coal load and there is a good draft, the stove could go red and beyond, caving out the stove wall.    

I was a fire chief's son.  I heard all the horror stories.  Be warned if the stove has glowing red parts, is chugging for air supply, and has lots of wood in it.

What do you have the stove sitting on?  It should be on something that is non flammable, such as a suspended steel plate, or a pad of bricks or stone on sand.  If the stove does fail and you do not have this, then you have all of those coals landing on dry barn boards.        

I support Roberto's more detailed description of putting mass around your stove. You definitely need airspace between the thin metal stove and the mass, so the metal doesn't overheat soon and fail.

Glenn Herbert wrote: $50 can get enough to make a section of wall feel warm behind you as you enjoy the stove.

And a trip to a local construction dumpster may yield a bonanza of 4" styrofoam pieces that you can put on the outside of the block wall, to be stuccoed later.

I made a rocket mass heater out of a meat smoker; it looks about like your stove set on end. I covered it with about 2" of cob/fiber/cement, and it has worked well the last 3 winters. Nothing like 400 pounds of brick and cob to act as a thermal mass.  If you did that though, your stove would no longer be portable, and you could take off the carrying handle.

Ferne Reid wrote:... I've heard of people building a fire brick box around their wood stove to hold and disperse more heat. Would that work here? How big could I make it before I'd lose any heat advantage?

I have used fire-brick, refractory cement, sand. Some people like soapstone.

My observation has been it is easy to 'hold' heat and it is easy to disperse heat. But these are opposites. Either you design a wood stove to heat up fast and immediately give off that heat [heaitng your home faster]. Or you give it a large thermal mass, which is slow to heat, which retains that heat a long time, and slowly puts heat into yoru home.

We have a two-barrel Vogelzang. They are rated at 200kBtu. We have operated it with cement lining and without.

With a thick liner, it is slow to heat-up and afterward when the fire has gone out it will stay warm a long time. Without a liner, it heats up fast and it radiates that heat into the house immediately. When the fire goes out, the stove cools quickly.

Eventually we added 50' of 5/8" copper tubing in loose coils, in the upper barrel. We circulate water from a thermal-bank downstairs, through this heating coil. We also have a second circulation loop that runs this heated water from our thermal-bank and through our radiant floor system.

We extract heat from the wood stove, we store the heat in a thermal-bank, and we transport that heat throughout our floors.