Michelle Beerli

In this article it has been stated that cob has a low thermal conductivity and for this reason it will absorb heat, retain it, and then dissipate it back out slowly; whereas, "fired brick absorbs and release heat very quickly".

I looked up the thermal conductivity of both cob and fired brick and they are listed at 0.6 W/mK.

Can someone please explain in more detailed why fired earth (fired brick) absorbs and releases heat quickly, while un-fired earth (cob) is better at absorbing and releasing heat. I have been searching on the internet but I cannot seem to find a technical explanation

Thank you and all best!

Michelle

Hi John, curious about the thermosiphoning system you have set up

John C Daley wrote:
I have wrapped a whole coil of 3/4 inch pipe around the flue just where the flue exits the heater.

Previous comments on this post have warned that setting a coil around the flue is dangerous...risking that a steam explosion can happen in the house.

What makes you feel secure to set up a coil around your flue? Are there conditions for which you can set up a coil system safely for thermosiphoning?

Hi all,

Thank you very much for your advice.
With the safety concern I have opted out of the coil design. I am considering instead to design the stove in the way that the video shows here:

Fast forward to  3:21 - 3:32 minutes

I could not attach photos, so sorry that you have to look at the video.

Has anyone used this system before? Is it a safer alternative to the coil idea?

Also, I am curious, do you have to buy a stove with the interior pipe already installed or can you weld one in yourself? Anyone done this before?

P.S.: In the mean time I will settle with the stock pot idea until I find safer alternatives

Hi Thomas, I am not sure how to directly reply to your post, so I hope you will be notified about my response.
First off, thank you for your help! I would like to respond to your questions and ask you some back for clarification; if that is ok.

thomas rubino wrote:
Were you hoping to pump that hot water for a shower?

We would like to live as much as possible without electricity. So the idea of installing a pump for us is out of the design. I was thinking I would have the copper tubes coiled around the barrel and attached to a large inox metal container. This container would hold the water which will circulate and heat up via the copper tubes. On the side, we would keep a bucket of cooler water so that we can mix the hot and cold water to the temperature we like. Following we would take a smaller metal pot to pour water on ourselves for the bath.

thomas rubino wrote:
A bare barrel RMH will be at or above the boiling point for most of its surface.
A large pot simply set on top of the barrel would supply plenty of dipping water.

It seems from your response that I would be able to collect hot water from both the copper tubing thermal syphoning system around the barrel and also from setting a pot of hot water on the barrel for boiling? Both would work efficiently? Would you predict that the water would come out steaming hot?

thomas rubino wrote:
Your copper pipe will need to be large... like 1" or so.  Your picture looks to use 1" .

I am a novice at this idea of thermal syphoning..how do you determine the size of the tube? For example, how would I know that a 1" copper tubing would be needed for a RMH's barrel diameter?

I am also curious if I should be careful about how small the bath house would be. Would you say that having too small of a bath house could be dangerous?

Thank you for your help!

Hi all, first time poster here. I would like to construct a small bath house that would we heated by a RMH (waterproofed with Tadelakt). Main problem with this idea is that I would like the RMH to act as a heater for the space/people and the water. I am not certain if the bell of the RMH would be sufficiently hot enough to warm water by setting up a copper tube around the exterior of the bell to create a thermal syphoning system. I have also read that the top of the bell does not get hot enough to quickly heat water. The copper tubes would connect to an open-top metal container located inside of the bath house; so there would be no water pressure issues.  Does anyone have any advice/experience with using this system? I am also open to different ideas...I mainly wanted to set the system up with a RMH for it's wood burning efficiency and heat output. Maybe a Rocket Stove would be an easier idea but I am worried it would not heat the space well as it is small. Also to note I am reading 'The Rocket Mass Heater Builder's Guide' by Wisner so I have a basic understanding already of the RMH concept.