Thailand Barrel Dome Build - $400 to completion (my labour free!)

[JimShortz]

Have you checked out this thread yet?
https://community.fornobravo.com/for...read#post17312

Now that is what I neeeded - thank you! :-)

[JRPizza]

Have you checked out this thread yet?
https://community.fornobravo.com/for...read#post17312

[JimShortz]

Help sought with a highly insulating door design...

I have a metal door with a closable gap underneath for use during firing and cooking, BUT, I want a higher insulating door to use when closing the oven up overnight after cooking pizza - ready to bake the next day.

I have seen one with percrete sandwiched between aluminium and with aluminium mesh around the perimiter of the perlcrete. That's a possibility, as is making one out of AAC blocks (or buying an AAC poanel to cut to size). Does anyone have any thoughts on this? Or other ideas?

Thank you :-)

[JimShortz]

Nearing completion - insulation with Perlcrete + full jacket of AAC insulating blocks completed. First firing of insulated oven coming up... :-)

Actually, to say "insulating with perlcrete" is a slight lie. In the Upper part of the dome where the "perlite" layer is deliberately much thicker it is actually chopped up chunks of AAC block offcut sat in a perlcrete matrix. It used up every bit of my left over AAC blocks (chopped up with a machette, would you believe - worked great) and that helped out a lot in filling the spaces - and used up all of the waste; double winner!

At the top of the oven the space for perlcrete reaches about 13cm, whereas only 5 cm on the sides where the oven is less hot. It seemed like the most efficient use of materials to me and I have got away with using only 100L of perlcrete by using the chunks of AAC in the matrix. Perlcrete is fairly expensive here, whilst offcuts are free. unfortunately I didn't photograph this part of the job...

[JimShortz]

This is where I am currently up to. I have begun insulating the dome with a combination of 5cm of perlite (mixed 5:1 with portland cement) and then a layer of shaped and tightly fitted 7cm AAC blocks - giving 12cm (5 inches) of insulation overall. There are actually two layers of AAC blocks on the front wall, but that decision has more to do with how things work out with my base building, the double domes, etc, - to create a sensible and simple shape when finished.

I've used about 50L of perlite so far, with 50L left to finish the main dome. I also plan to insulate the entrance dome, so may need to buy a bit more perlite to finish off. I'll post more pics as it moves forward. :-)

Once the insulation is completed I have a friend who will do the final waterproof rendering for me (with glass fibres mixed into the base layer. I am no builder, and I think rendering a dome may be beyond my skill set. I'm fine sticking blocks together, but rendering that shape might be a step too far, lol.

I know that there aren't many who have used AAC blocks, so I will also post some performance/heat retention figures once th baby is in use...

[JimShortz]

That's great! I could not tell if there was insulation or not. Looks like you are right on top of things.

Thank you. This forum has been super helpful. I did a lot of reading on here before launching into the project...

Here's some more photos, showing the chimney hole and the chimney in position, as well as my first fires. I'm aware that not everyone thinks it is a good idea to fire before insulating, but I couldn't wait!

The first fire reached a max of 180C on the upper side walls, but I got to 450C on the second - oops, lol. Nothing cracked and all good to go. I think it helped that the main dome had already been built for 2 weeks and had sat under the hot Thai sun (dry season here), so all of the blocks were very dry already anyway.

Insulation layers post to follow... :-)

[JRPizza]

That's great! I could not tell if there was insulation or not. Looks like you are right on top of things.

[JimShortz]

A few pics of stage two of the build - all three fire brick domes and front and rear walls completed, and a well-earned beer to celebrate, lol.
I only wish I had taken some pictures of the inside of the dome after I went through the contortions required to point it up properly. It looks great, if I do say so myself, and I didn't photograph it! :-(
I have now moved on to begin the insulation - a combination of 5cm of perlite followed by a layer of 7cm of aerated concrete blocks (AAC) - the same blocks as form the two insulating layers beneath the hearth. I will add a further post to share progress on that very soon :-)

[JimShortz]

Nice progress! It looks like you might have followed the plans that don't specify putting insulation between the oven floor bricks and the slab/hearth. If yes, you may have problems maintaining temperatures due to thermal losses to the large concrete heat sink. Check out the link below to a thread started by a new member with what looks like a similar design.
https://community.fornobravo.com/for...ven-hot-enough

Actually, if you look closely there is a 12cm slab, followed by 14cm (two 7cm layers) of highly insulating AAC (Aerated Aotoclaved Concrete) blocks to provide a very high level of sub-hearth insulation. The few red clay blocks you see on their side across the front are there just to fill in a gap and aren't beneath the hearth - you can see the AAC blocks down the sides. :-) I've attached a clearer shot here too.

These blocks have been discussed quite a bit on this forum and what convinced me to use them was some data provided by an apparently knowledgeable poster on here, called Carl: "I'm using Thermalite blocks for my hearth insulation (probably very similar stuff - another brand of AAC). Their website gives a value of 0.11 W (m.K) - the value I found on the web for vermiculite concrete was 0.094 W (m.K). AAC bricks actually have a lower conductivity than insulating firebrick, and since the blocks have a very similar conductivity to vermiculite concrete, I've decided to use them."

The quote from Carl comes from post #24 in: https://community.fornobravo.com/for...der-slab/page2

[JRPizza]

Nice progress! It looks like you might have followed the plans that don't specify putting insulation between the oven floor bricks and the slab/hearth. If yes, you may have problems maintaining temperatures due to thermal losses to the large concrete heat sink. Check out the link below to a thread started by a new member with what looks like a similar design.
https://community.fornobravo.com/for...ven-hot-enough

[JimShortz]

After all the work, and many hours making this beast, I thought I might share a little...
I'm actually a little further on than these photos, currently enveloping it in 12cm or so of insulation. The pics tell the story so far I think, although I failed to photograph the substantial 12mm rebar matrix that is within the 12cm slab. The internal hearth within the main dome is 90cm x 90cm.