Coydon Wallham

Caitlin Steve wrote:I’m one of those noobies and maybe to give context for you noticing that trend… I’ve seen permies on Reddit/google/chatGPT. Basically anytime someone asks “where can I find off grid singles” the interwebz sends them here. That’s how I discovered permies and why I don’t have much posting history. I’ve been learning a lot through the different forums but feel too novice to contribute to the conversations. It’s hugely educational for me though. The singles forum was just what got me
in the door and I’m sure in time I will have great contributions to share but it can be intimidating for someone with less experience than all these permaculture gods and goddesses out here sharing all the cool things that are so fun for me to be exposing myself to. It’s a whole new world and I feel like that’s a mission everyone here shares- community and converting people to a better way of life and the singles forum is a great introduction

Don't be shy in asking questions on any topic that interests you in any of the forums. I'd suggest reading up on the 'Wheaton Eco Scale' here- any questions that help everyone understand better what it takes to encourage people moving from "level 1" to "level 2" (or even 0 to 1)  would be pretty central to the 'mission' of this site...

thomas rubino wrote:The tighter the seal the better it will work.
You could fold up some foil to cover the feed and place your firebricks over that.
I suspect both piped mass and a strat chamber are very similar in heat loss, if allowed to draft.

A piped mass might flow better, but by volume, it is tiny,
A strat chamber is huge in comparison.
Ultimately, both rise through a vertical chimney pipe.

I kinda suspect the foil would be too much fuss on a daily basis for most users. The plug for the FPH is a well crafted piece. I'm surprised Paul hasn't done more bragging about it, maybe he's just too shy and timid to say anything. But seriously, you should check it out, this might be another design that could be offered by Dragon Tech, if there is enough of a J-tube market out there any more. I'm just curious how much draft actually will still get around two firebricks.

For piped vs. stratification, both systems have say an 8" exhaust going up. The ducted system is designed as one big chute, usually ascending through the entire mass (particularly if following the Wisners' advice from the Builders Guide). I think the strat chamber would function as a bit of a plug compared to the inverted sink of heat that would flow through the ducts. The bottom of the strat exhaust is pulling the coolest air, the heat of the mass will work with the warmer air to stay above that level and resist flow out the exit...

Am I correct in my understanding that it is much more important to block the flow in a ducted mass than a stratification chamber? Seems the ducts would be much more efficient in drawing heat straight out of the system.

I'm not sure how familiar you would be with this concept Thomas, but I was at Wheaton Labs when Caleb designed a custom plug for the feed of the RMH in the Fisher Price House. I've since been wondering if the difference between something like that and the two firebricks I use would be measurable...?

I'll temper my previous statement by saying that shapes like yurts and domes don't suffer much of the problems with wind as more blocky buildings do so that might not be a large concern in your case, but there would still be clear benefits to having the exhaust exit as high as possible.

I've never heard of a chimney that was too tall that it worked negatively against draft...

Kendal Webster wrote:I'm still debating where to place the exhaust. With any luck I'll start a layout using tape tonight. This will help my visual brain see things better. Also another chance for feedback from the experts here before I start buying materials.

Your picture showing exhaust going up at an angle gives some extra ideas, but the very central part of the dome will not be an option, but any point up to where the loft will eventually go is available. We will see how it all comes together in the next several weeks... or as long as it takes!!!

Discussions I've seen on RMHs with side wall exits have been about irreconcilable problems, sounds like it is always more rewarding to put time in figuring out how to have exhaust exit through the roof (or highest point available). More efficient in radiating heat from the exiting gas into the building, and avoiding problems with airflow around the building. Looks like plenty of room in the triangle frames adjacent to the cupola, the closer to the peak the better...

No need to have the RMH in the middle of the footprint with the pipe running straight up and out through the center of the dome top:
Also, with the bench as a stratification chamber, the exhaust can be right next to the Liberator on the central side of the bench.

I'm trying to picture what your interior ceiling looks like that it would be difficult to run some 6-8" HVAC ducting up and out of or near the center of the dome...

thomas rubino wrote:
Shorty is a superior design, with more versatility and lower costs.

Do you explain this comparison in your book? I'm about half way through...

Peter van den Berg wrote:
Regarding your end question: yes it is, provided the calculation is done in a proper way. See the space above the riser as an imaginary ring. Think about it this way: the gases, rising out of the riser need to go through a 180 degrees bend in order to stream down.  When this ring's circumference, multiplied by its height is a figure that is twice as large as the riser's cross section area, then it's about the right size. Just by giving the gases ample space to round the bend without too much friction means a possible pinch point isn't there at all.
The same thing happens at the exit, the distance between the floor and the end of the pipe works the same way, although the change in direction is just about 90 degrees since most of the colder gases stream along the floor. So, in theory, the surface area of that imaginary ring should be at least 1.5 times as large as the exhaust pipe.

Calculating... the 8" pipe's csa is 50.26 sq. in. So, the imaginary exhaust ring's surface area should be at least 75.4 sq inch. Devided by the circumference gives the height of the ring. In your case, that would be 3" as the minimum distance from the floor, provided the exhaust pipe is free all around. As said before, the depression might be a negative factor.

The exhaust pipe is constrained some on the sides around it. Would cutting a vertical slit in the pipe and bending it back to enlarge the opening on the side toward the firebox be enough to increase the draw ability, or will it be necessary to break the cob, cut and reposition the whole pipe?

Glenn Herbert wrote:I don't see including some 1" iron pipe in the floor as doing enough to be worthwhile.

I ditched the pipe idea and put a sheet of .5" cement board on top of a grid of cement bricks to form the base of the firebox/barrel. The face of the bricks has been cobbed over, with channels left between them.

The bottom of the stratification chamber has wine bottles between each brick on the first course, completely cobbed in by thermal cob in the floor of the bench. Not sure if there will be any insulative benefit (from the bottles), but it has decorative qualities and saved on some cob requirements.