Hi All,
I was stacking whole dense firebricks the other day and put together a core and riser entirely of brick.
Now I’ve decided I don’t want to deal with that heavy old mass in my combustion unit so I’m setting out to purchase fiber board and blanket to make my rmh more efficient and easier to use.

( 1. ) I gathered that at the minimum the 8 lb blanket was necessary in order to be in direct flame contact. Should I get the half inch and wrap the inside of my pipe twice or will the inch stuff joined together flush at the seam be better?

( 2. ) Do I need the 2600 degree stuff or is 2300 sufficient? Wondering on both the board and blanket.. I feel like I should know this and I was planning on 26 for good measure but.. maybe I could save a few dollars. (Edit: Thomas, I just saw your response from a week ago in a related thread outlining the products you had purchased and planned to use so I guess 2300 works..)

( 3. ) Regarding the board I think I can make a tunnel to spec. and put some split bricks for the feed so I don’t know what to ask but any advise would be appreciated. Is there a preferred method of fastening the board together at right angles or should I be thinking of my brick / fiber board core in a different configuration. Maybe board for just the ceiling and rear of tunnel/base of riser area. I know someone has done this before me. Which part of the Feed/tunnel can be fiber board?

thanks I’ve been dreaming this into existence for five years and now I think it’s going to finally come together.
I live at 5040ft east of Ashland Oregon. The winters are long. My cabin is up on pier and post so I can’t build mass inside at least not yet. I’ll be working on my foundation soon hopefully but for other reasons. It’s shifted over the last 30 years. I’m putting my first Rmh in a greenhouse. It’s a 12ft diameter dome. I’d like to heat the whole floor. Any ideas for a short wide circular bell that can be walked on?

You guys rock thanks for paving the way

Hi Jesse;  Welcome to permies!
Yes, 2300 F is fine.  You want at least 1" boards. It was suggested that 2" for the roof would be extra nice but not required.   For the blanket go with the 1", I,m planning on the #8 but was told by pinhead that he used #6 on his original 5 minute riser and it is still working today.  Peter van den Berg also thought that #6 would be fine.
I asked Matt Walker how to join ceramic boards . He uses aluminum foil around them and uses red clay brick as a backer.  This is the item # at ebay for the board i have( 222715872389)  it is 39.4" x 19.7" x 1" thick $95.60 delivered.  This along with split brick for the feed tube is enough for an 8" J tube core.  Sadly the blanket comes in 25'-50' rolls for about $95 delivered
About your greenhouse.  If you want to heat the floor you will have to insulate from the ground . Most people use a raised bed .  You still need to insulate from the ground but your not burying insulation underground.

Ok so I’m about to order the 2” board in the nearly 20x40“ dimension you described getting in the 1” thickness.
In regard to the blanket, I can get the 2300* in 8# or 6# the denser is 5$ more but I don’t want it to be dense I was thinking. And since the lighter one should hold up as it has from others experience there’s no need for me to think that the 8# one would be better. My conclusion is that the 6# will actually perform better. Just wanted a second opinion before I pass up the 8# for five more dollars.
Also the blanket comes in a 48” width and was considering getting more and having the ability to make a 12” heat riser or a 4’ long one of any diameter. I’m guessing most people don’t end up needing to make it longer than two feet?

Guys, careful with two inches and heavy weight superwool.

Here's what Peter said recently.

http://donkey32.proboards.com/post/30096/thread

I bought the 2” x 19.7” x 39.4” ceramic fiber board at 2600* because it was only ten dollars more than the 2300. the two inch wasn’t a whole lot more than the one inch either, and I read it was preferable to have the double thickness at least in the tunnel ceiling so why not throughout?
I also bought the 1” x 24” x 25’ of 2300* 6# blanket since it will be less dense and apparently is easier to bend and still holds up. I hope my fires not hotter than 2300*.

Any reason not to do a ten inch system? I can see that 8” is going to be easiest to construct from the board that I got and I already have some 3’ lengths of 10” ss duct so maybe I’ll try bigger another time once I succeed with this.

Hi Jesse;   2" ceramic boards will be super and what the heck 2600 F will be good as well. #6 blanket is fine. Your riser temps will not reach 2300 F .
As far as riser height , hardly any would be 24" , mine is a total of 51" counting the 16" drop at the core. 
My new riser is planned on being 64" counting the core
Not to many 10" cores out there.  I almost designed my new one around a 10" but decided to sick with 8" for the availability of pieces.

I bought myself five gallons of sand for two dollars so I can make some test bricks. I’ve never made cob before not sure why. Probably since I didn’t have any sand. I’m going to do a soil settling jar test to see how much silt might be in my clay soil. It seems very clay rich. In a week I’ll be able to put my core together. I’m going to cut an 8” x ~20” for the base. 10” x 20” walls and 12” x 20” ceiling which I will cut the rear part off of for the back wall. I guess I will make the feed from split bricks and put some of the blanket around those. I know a source of 2” soapstone slabs if I can get them I’ll build my bell bench/raised bed from stacked soapstone so it won’t take long to dry.

Jesse, any construction supplier should be able to sell you a ton of sand for 20 bucks. Plus transport.

Jesse Baker wrote: I know a source of 2” soapstone slabs if I can get them I’ll build my bell bench/raised bed from stacked soapstone so it won’t take long to dry.

I'm very envious of you Jesse... Soapstone is a fabulous storer of heat. I obtained some chunky blocks of it several years ago and used to place them on the top of our box stoves to act as thermal storage. They worked very well, still being warm many hours after the fire in the stoves had gone out.