I've checked the numbers, there's nothing wrong with your maths. You can get away with one single and one double fire a day in a 10" system though, that would deliver enough power to heat the house properly. Or build an even larger one, a 30 cm or 12" system. The bell size would be huge too, it seems to be a viable option to add a bell bench.
But I'm inclined to think your problem is the insulation of the house, as there's none. Better start to insulate the hell out of it. It's definitely work but it needs to be done just once, as opposed to processing enormous amounts of fuel every year, again and again.
For example: our house is about 650 m³, passive house quality insulation value, temperature difference about 28º C during two weeks per year (we like it quite warm). We use a 15 cm (6") system and alternating single and double firings to heat the house. Usage of softwood per winter: 3 m³ or just short of one cord, provided my calculation is correct.
posted 2 years ago
Thanks for the replies.
Perhaps the insulation number is my issue. I chose 1.6 insulation factor because it was a guess.
Since a dome is all roof, I put grace membrane over the entire dome, so it is literally air tight with the exceptions of doors and windows. ( grace to seal around them too)
Since it is built from 2x6 lumber, my insulation is R-21.
All the literature I have read says a dome requires 30-40% less BTU to heat and cool. Add to that my complete membrane; I believe I should be very close to that.
Would R-21 and an air tight home give me a better Insulation factor than 1.6?
I currently stay in an mobile home that is VERY drafty and poorly insulated and my only heat source is an "Old Timer" wood burner with an 8" flue. This thing will run me out of the house if I fire it up and open the draft. I can only let it idle. I currently am burning around 4 cord per heating season.
I would like to use a batch box with a bell. I have enough room for a bench if needed. my floor is unfinished concrete, fiber reinforced at 4" thick. Height is not an issue because the ceiling at that location is 14'.
Thanks again for any help.
I have bought the book from Paul about building RMH. Is there a book that covers how to build batch box with bell? Maybe a set of blueprints for a known good design?
The ratio of system size to mass will vary depending on your climate. If it gets cold and stays cold for days, weeks or months at a time, you want a larger mass to even out temperature swings in the space. If you are subject to frequent temperature swings, cold one day, warm the next, you want a smaller mass that will respond quicker to running the fire or letting it stay out. I couldn't tell you the actual masses to use for a particular situation.
posted 2 years ago
Thanks Glenn. I live in Indiana so it may be 65 one day and 30 the next. I have access to plenty of wood so I am not concerned about the amount of wood I use, except for the simple fact that I don't like wasting it either.
My wanting to use this type of heater is that it burns so much cleaner and is more efficient with the fuel it does use.
I can fire three times a day easily.
Currently I burn continuously at an "idle". It is VERY dirty and I get ALOT of creasote build up. Bad for the environment. Bad for the flue. And I use a lot of wood.
I could heat with propane, but I really like the wood heat.
Thanks for explaining about the mass sizing, I think I should keep the mass to a medium size because of the frequent changes in climate. ( Oh no....climate change)
posted 1 year ago
Okay. I think I figured out what an insulation factor is. It is called a K-factor here.
You can figure it by dividing the thickness in inches, by the R-value.
A straw bale is roughly 16" thick. It has roughly R-30.
My dome has R-21 in 5.25"
I hope this will help someone!!!
posted 1 year ago
With the new information, numbers look WAY better!