So sad. There's a gap in the masonry in the old fire place in our house. Not easily repairable. So, we have a fire place, but can't use it. Also, this fireplace appears to be built or modified with energysustainability in mind. There's a bench right in front of the fire place that is metal on the bottom and cement on top. The fireplace is curved for heat to leave, the back surface being reflective. But alas, the chimney needs internal repair and I'm not THAT thin and my arms aren't THAT long.
So, since we still want to be able to heat with wood- what to do?
My husband has voted for a rocket mass. However, I have concerns:
1. As far as I know, I'd have to do it. If someone builds them and wants to come take over (we'll even provide room and board and help) if they know what they are doing, than great! But, I don't feel comfortable standing on a 2-story roof dropping pipe down the chimney!
2. Weight. It's not on a foundation. It's on the first floor above a basement, so too much earth could be a problem. There is cement and metal, which weighs a fair amount now, but something to consider, especially when the cob is wet. Perhaps there's another material that can be used?
3. Permitting- it wouldn't be...so there's that. And, I want to make sure there's 0.000% chance of leakage of bad gases or burning down the house. The bench will be on top of a wood floor. Which brings me to the point of wanting a good clean out.
4. Having enough wood and storing the sticks so they don't just rot away. I don't want to spend hours chopping wood to stick size. We have a windbreak and it makes a pile of stick wood every year, but I plan on having one out-door too and I don't want to run out of wood, especially in the middle of winter. Then I'd have to go around and buy fire wood, then chop the fire wood to rocket mass sized pieces. Now, if the rocket mass used fall leaves too or could stomach wood chips...
I've been considering a stove insert, but those are $$$$$$$ and not as efficient as rocket mass, not to mention the whole needing to buy wood and wood prices are likely to rise in the next decade since for some reason many people in Ohio thinks cutting down trees is a good idea.
So, basically I'm turning to the experts for advice.
1) There's not much of a standard RMH that can't be done by one ordinary person willing and able to follow instructions. A few bits would be much easier with two, like lowering the barrel over the core. As you describe your chimney, it sounds like any use at all will require a liner, which you may need to hire out... so not quite relevant to RMH concerns.
2&3) Weight is a consideration. There is really no getting around it, as you need mass to store heat. It is possible to minimize the mass and accept a shorter flywheel time. The best solution will depend partly on the arrangement of the floor framing under your mass location. If the bench will cross a large number of joists, each one may not be overloaded. Pretty much, if you could safely install a king size water bed, you can install a RMH with bench mass. You may need supporting posts and beams under the mass if your framing is not optimally laid out. Code would require masonry support to the basement floor, but in your case I would be content with actual safety over blindly following code. You do absolutely need to isolate the hot mass from wood flooring and framing, with air circulation spaces.
4) Enough wood... that is something you will need to determine by actual experience. I might plan to buy a load of firewood for the first winter, and store it safely to dry out. You will see how much if any of it you need to use that season, and if you have leftovers, it will be beautifully dry the second season. You don't necessarily need to split the wood very small; Ernie Wisner uses wood of the smaller ordinary stove range (3-5" across) and says it lasts longer between stokings. If you have deadfall branches too, you have a full range to pick from. I would just split the bigger pieces over 5".
Building a functional wood storage area can be as simple as making a 2x4 frame (with floor framing to hold logs off the ground) and fastening a sheet of plywood or other roofing on the top. Locate it to get as much sun and air as possible while being conveniently near a door for fetching wood. The weight of the wood will give it stability even without foundation anchors. If you have flat stones to put under it, that will help keep the damp away.
A place to store the requisite wood might be easier if I could chop it fast and simply. We are talking 1" sticks with small branches everywhere!!! I am planning on cutting out all the thorny-like bushes, so I can do it without injury, but still- lots of wood that needs to be chopped to like a foot long. How do people do this? Bundle it all together and then chainsaw as a cluster? I don't have a chainsaw, but I do have a circular saw that might help a little. Thanks!
Also, is it normal for fireplaces to get permits just to line an old chimney? I'd love to get it working this year, and then figure out the efficiency increases later, but at least have an alternative power source, if need be.
Another thing is that: is there an alternative to RMH that is nearly as efficient and not nearly as intense? I've heard of efficient grates and have contemplated the ideas like that. I mean, the chimney is going up through a mass 3 stories (2 actual floors and an attic) so the heat would be dissipating up like 25 vertical feet, which is probably a lot more efficient than a 1 story house chimney in gathering the heat. Not to mention the orientation is angled to reflect heat outward and it does have a warming bench. I can imagine that if the average fire place is 50% efficient, this already being at 65-70% (if it were working), So it might not be the best candidate for an RMH...
The average fireplace is probably somewhere around -5% to 5% efficient... that is, in certain conditions they can draw more heated air up the chimney than the wood produces. Yours with its features might be twice as good as that.
I'm sure there are areas that require a permit to reline a chimney, or do anything more involved than painting. Depending on the regulatory attitude of your locality, you could have to deal with permits and inspections, or just hire someone to do it and nobody cares. A contractor who knows what he is doing will know about any permits.
There are folding tables with a way to mount a circular saw upside down under the tabletop. These can work like a small table saw; they would not be much good for big jobs, but probably the safest way to handle small stuff like you describe. I wouldn't bundle the sticks, but put them through one at a time, for safety. A bundle of small stuff shifts and jams very easily. If you had a well-braced cradle to hold sticks and a bow saw, that could also work well, though slower than a motorized tool.
To update on SOME of my questions. I did more research, but I would LOVE verification from the experts.
The average weight of a rocket-mass heater 5ft long is like 1800 lbs. The average weight of a cast-iron wood-burning stove is about 400 lbs. 1800 lbs would probably exceed the floor weight limit 4-fold. So, I thought I would think about making it out of fire brick, but that only takes the weight down to 650 lbs. Still too much for my comfort. Now, being realistic: the ductwork will go up 30ft of masonry structure before exiting the house, which is like a 30ft long vertical mass of a rocket mass. The problem is: vertical, which means if the air starts out really hot, it moves really fast and spends less time sharing it's warmth. Any ideas? I was thinking I could do a 3ft firebrick-mass bench to get the temp down a few hundred degrees. I was also thinking about ways that I can more efficiently remove heat from the barrel. Nothing novel popped into my mind yet. The most I was thinking is curling pipe around it and having the inlet along the floor and outlet above the fire place (maybe shaped like a dragon for the AWESOME factor).
Second is hazard. The fire area (barrel and inlet) can remain in the fireplace, leaving only potential duct work outside the fireplace. This would also allow for doors to close off the super-heated parts if small kids are around. I could possibly hook up some small fans to the screen doors this could potentially have, also increasing heat circulation. Again, any input would be great!
The third thing is wood. I do not want to take power tools to make my wood I decided because that means I use electricity to refine my biofuel. Doesn't make a huge amount of sense to me. However, I found if sticks are sufficiently dry, I can snap them pretty easy, especially if they are the good type of wood (not the invasive branchy, thorn-like stick thing that lines the wind-break currently). I estimate I could get about 1 cord of sticks per year. My house is about 1800 sq ft . I am compensating with as much insulation, close-offs, and passive solar and heating as I can, and I am pretty sure the bedrooms will continue to be heated by space heaters. We also work out of the house 4 days a week, needing less heat for those hours. I think the one cord will be enough for what purpose this will serve (i.e. down-stairs heat for 2 hours x 4 days + 24 x 2 = 56/week x 24 weeks/year).
My biggest qualm now with doing this is that if all I can get is a 3ft pad before the house starts breaking, then, is it worth it? I think at that point it might be cheaper and more efficient, faster, and easier to get a wood-burning stove with a little blower, but I'd be happy for someone to convince me otherwise.
Glenn, I've heard those statistics before, but I have not heard the details, therefore I am skeptical. If they were so inefficient, then how did people survive when they were the only source of heat? Why would they be the imagery of a warm winter home? It doesn't make sense. I have used fire places before and sat around them for the yummy warmth too. How could I do that with -5% efficiency? It seems these numbers might be factoring a fire place used 5 times a year and otherwise let sit with inefficient doors or damper. Then, I could understand- it's a hole in the house's insulation. However, an actual working fireplace that's well positioned (like ours is) and well maintained and used I can't imagine fitting that category.
A big old fireplace can draw lots of room air up the chimney, and if this air is already warm, it has to be replaced with cold outside air through drafts. The reason fireplaces could make winter houses tolerable was that they had a different definition of acceptable, and knew how to make the most of the heat available. Wingback chairs were not just stylish, they kept the cold air away from your back and trapped the heat radiating from the fire.
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
Wood issue: problem resolved itself. You see, I found, once I started gathering wood, that my stomp-kick can break dry sticks up to about an inch and a half diameter, which is kind of what you want for a RMH. Now, I did temporarily atleast go for a high efficiency wood burner, so I need bigger stuff for continuous fire, (long story not yet over.) But I am able to cut down on my wood needs and get things going faster and hotter with what I gather without a need for a saw. If I practice more, I bet I can get my stomp kick to break 2-3 inches of dry stuff, but maybe I'm dreaming a little on that. The stuff I can't break but in my diameter range also tends to be the thorny stuff I'm trying to get rid of and replace with nicer plants.
Attached is a picture of about 15 minutes of gathering/kicking from the driveway, including two 5 ft sticks I cleared out of a hedge in fall.
Work smarter, not harder.
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