heat a montana home all winter with a half cord of wood

Nov 27, 2017 11:12:30

To give an amount to compare that to, we use a 1970's wood furnace to run the radiators, not only is it old and inefficient but it's not in the living area either so all the heat directly from it and the chimney is pretty much wasted. The house is a 1887 1330sqr ft single story brick contraption with seriously leaky windows (double glazed) next to nonexistent insulation in the attic and interior boarding and polystyrene on the walls. To heat this for the winter and to provide hot water all year round we use just over 2 cords of wood. The outside temps will hover under freezing for about three months and will be under 10C for 6 months, Heating is needed for between 6 and 7 months. We don't have anything fancy like passive solar the house runs E/W and 4hrs of daylight and pretty much no sun in December isn't going to do much. Our biggest enemy is the wind, we live in a very windy area, and due to the design our eves are not really long enough so wind can and does get up under them.
Now we do not keep the house what most people consider warm, we keep our computer room at 20C but the rest of the house drops down to 10C which is the temperature required to keep a fridge/freezer running. A RMH if we could get it through code would be amazing in this back room, but I don't see how it would help the rest of the house from freezing.
On a slight note, how are RMH chimneys swept? this isn't optional here all chimneys MUST by law be swept twice a year and it is done by the council so there is no way round it.

Nov 27, 2017 12:06:56

Skandi Rogers wrote:On a slight note, how are RMH chimneys swept? this isn't optional here all chimneys MUST by law be swept twice a year and it is done by the council so there is no way round it.

Most rocket mass heaters have cleanout ports for the ash. No creosote.

Nov 27, 2017 13:04:56

paul wheaton wrote:
- reduce the size of the roof exhaust from 8 inches to 4 inches so when there is not a fire, there is less heat escaping at that point

I have a situation that is a bit different, and I was wondering if the reduction in air volume could justify a reduction of the flue size, but also if I could switch to a powered vent blower and force the exaust out the side of the house like my 97% efficient propane furnace is. Better if it's DC so I can run it off a solar panel & batteries, but better still if I can run it in a loop around my basement. Can I put a RMH in a partially finished basement, and run the exhaust flue around until it's cool enough to use PVC vent pipe? Does anyone know how much of a volume reduction a temp drop from 450 degrees (roughly what my regular woodstove puts out) to 100-150 degrees creates? I'd like to be able to reduce all the way down to a 2 inch flue pipe as I run it around the basement.

Nov 29, 2017 00:16:10

paul wheaton wrote:I think an enclosed porch for the front door would probably help a lot too.

My home needs that also!
I find it crazy that homes in colder climates are built without enclosed porches. Don't need to heat them, but to act as an airlock is very important.

paul wheaton wrote:In another thread, there were people who cast doubts on how little wood it would take to heat a three bedroom montana home.

Frankly, I'm getting kinda sick of proving shit.

Here's what how I think of it.
If the TechnoNerds want to compare, then use the standard density for the wood Paul mentioned he burns, and then compare that to the wood YOU burn.
I have access to spruce, jackpine, (Black/White)poplar/alder/dogwood/aspen (around here, everyone calls them something different, but we really don't know what they are), some birch, LOTS of willow.

Everyone burns jackpine or poplar. It is cheap, plentiful. Pine is hotter than poplar, but so what, we have so much, it matters little, other than you stoke 20% more. We leave the birch for the wealthy.

Now if I want to compare, as Paul did, I would use the wood I normally use. Simple. And if someone needed to compare, use the standard weights, and convert to their wood.
Just like comparing oil, electricity, propane, LNG. it is all BTU.
Paul heated his home with about 11.2MBtu of available energy. That is what HIS house/location required. and each home is specific. Mine might be more or less insulated/sealed up than his.
Remember, in NYC, the skyscraping office buildings have NO heat source. An example of specifics.

Now as for proving... just have someone measure the temp/cfm of the exhaust of the RMH vs the efficient wood stove, and you will see WHERE the efficiency lay. From that, and knowing the available BTU of wood, you can tell how much energy is being kept in the home. If you can hold your hand/face in the exhaust of a RMH, that means most heat is left inside. I know folks who COOK inside the stacks of a modern wood stove.... a LOT of heat goes out the chimney.

if a RMH has cool exhaust, it is reasonable to assume the "energy" is in the house!

as energy is a constant, we can then understand that by knowing the exhaust temps and the available BTU of wood, we can see how much/little heat loss there is, and THAT will PROVE the hypothesis that a RMH is far more efficient than a wood stove, oil furnace, LNG/Propane furnace, or electric heat.

My question is:
Can one RMH heat a modern house, basement and main floor, in Central Saskatchewan winter?

I laugh when folks say "It got cold last night... -17F! My idea of cold is -35 to -45. C or F, it don't matter.... it is dang cold.
I think we need to compare "heating degree days" at each site to get a feel for how it compares at different locations.

Would I need to have a fire twice a day?

my oil consumption equals 2500Lx34kbtu= aprox 85 MBtu X 50% efficiency (OLD furnace, should be replaced) = 42.5MBtu needed to heat my house
To replace that, I would need to burn at 100% efficiency, 2.3 cords of jackpine, or 2.8 cords of white poplar/aspen

so, looking at Paul's experiment, using 0.56 cords in his warm winter location, I think Paul's numbers make sense.

just to give you some comparisons. a friend has an outdoor boiler for hot water heat. he burns 15 cords of Jackpine a winter. A neighbour has a Valley Comfort Stove in his basement, burns 5 cords of Jackpine, and 45gal of heating fuel in his backup. I burn 2500 liters of oil in my furnace.
I have an issue with insurance, so can't have wood heat yet, but am working on it.

I am still trying to figure out what system is best for me. a RMH on the main floor is out, unless we build on.
Something in the basement that requires only TWO tendings per day, would be best, I think.

Nov 29, 2017 04:02:23

I have no doubt it can be done, the real question is should it be done.

I once had an argument with the State of Maine Planning office who claimed that heating a home with compost would "never work", even though it has been proven since the 1970's. However here is the sticky point. While it can be done, after crunching the numbers, I concluded that FOR ME it was not worth my time to do. Despite having ample amounts of compost produced by my sheep and logging operations every day, the truth is I have ample amounts of firewood. The amount of time it would take to move manure and wood in lifts, run my tubing, etc, in far less time I could just go out and cut firewood. That is because I have the forest acreage and the logging equipment to do so.

Now in this case, Wheaton labs is helping others who may not have these resources, glean the most of what they can out of what they do have. That is a lofty endeavor and worth A LOT! And lets not forget the cool factor is incredibly high too.

But while I do not have interest in building a rocket stove, do not get me wrong, I do not have any interest in boasting about cutting 80 cords of firewood to heat my home every year like some of these outdoor wood boiler guys either. FOR ME, the middle ground is using a pot bellied stove where the wood must be cut half as small as typical firewood. Again that is me, and my big house in Maine consumes about 4 cord of wood.

Overall, it is the chicken and the egg question. Over on a different site they got upset at me because I think it is insane to spent $12,000 on an outside wood boiler and burn 80 cord of wood in it, when they could have invested that same money in new windows, insulation and doors and been better off with a much smaller, less expensive furnace. I am pretty sure one guy wanted to come to Maine and punch me for pointing out how silly such a thing was. In that case they are just using cheap BTU's rather then keeping btus from going out the window...literally. Big, burly outdoor wood boilers are cool though compared to insulation and windows though...I get it...not the choice I would make, but I do get it.

Nov 29, 2017 08:15:31

I think there are dozens of factors to fiddle with still.

Dick Proenekke, the "Alone in the Wilderness" guy, would heat his cabin up to 40 degrees. I've met some people that feel that that is plenty warm.

So I made it a point to not let the house get under 66 degrees. And when we did have a fire, I was usually shooting for getting the house up to 72 or 74 although sometimes I overshot to 76 or so. And this thermometer is placed so it cannot possibly be influenced by radiant or conductive heat - so this is strictly convective heat. Therefore, two very important measurements for the whole thing: cords of wood and indoor temperature.

And this brings up another critically important thing. I am measuring ONLY convective temperatures. If I was sitting on the mass, I could let the air temperature drop a lot and I would be comfy. Feel the mighty power of THE MOST EFFICIENT TYPE OF HEAT: conductive heat.

Further still, I work at a desk most of the day and jocelyn works at a desk most of the day ... I could rig up this stuff:

With this little trick alone, I might drop the air temp in the house down to 55 and probably go from 0.60 cords of wood to 0.25 cords of wood. And that would probably still include warming the house up every week or two for guests or something.

The critically important thing here: I did the work. And the people that are doubting it have never used a rocket mass heater. At the same time, there are a LOT of people that are using rocket mass heaters and getting similar results. And then the biggest:

0.60 cords of wood

averaging about 69 degrees F

If people doubt the numbers, they need to get a rocket mass heater and do their own experiments.

Nov 30, 2017 10:20:07

We live in a straw bale house in Eastern Ontario. We use a mansonary stove to heat the two story house. We have a few too many windows and go through about 3 cords of hardwood a year. I have my Studio/bunkie about 1/2 done. As in the roof and slab floor. Next summer let it be done!! I will be putting in a rocket stove. It is a round structure and will also be strawbale. I am so looking forward to burning less than 1/2 a cord! I was going to put some tubing through the floor, not sure if it is going to be radient hot water/glycol or just hot air. Still thinking.

d

You ought to ventilate your mind and let the cobwebs out of it. Use this cup to catch the tiny ads:

The new kickstarter is now live!

https://www.kickstarter.com/projects/paulwheaton/garden-cards

Sepp Holzer Desert or Paradise Documentary

SKIP kickstarter permaculture and homesteading skills