Floor insulation

[Dr. Leslie]

Hello...I am in Mexico and having trouble finding a suitable floor insulation to be placed under the floor bricks.

Is it possible to use a material that can be acquired at a hardware store (Home Depot) such as "sheetrock" o "cement fibreboard"?

[Chach]

unfortunately no you will not be able to find this insulation at a big box store. Cement board and the like are not insulators and have similar properties if not the same as concrete and would become a heat sink rather than an insulator. Check HVAC supply houses that deal with boilers. Places that sell refractory cement also can help. Distribution International has it for sure but not sure if you have a location close to you. Online is another source but make sure you purchase the correct type needed.

[UtahBeehiver]

Possible raw materials that can be used instead of high tech ceramic blanket (dome) or CaSi board, (floor) is vermiculite or perlite. If you can obtain either, you mix with portland cement in various ratios depending on location on oven. If you find either of these materials get back the the forum for additional info.

[Dr. Leslie]

Thanks a million!!

I managed to contact the chief maintenance engineer at a factory near me, one that uses boilers, and he has helped me with the ceramic blanket.

1. I have not been able to find CSI board.
2. I have not been able to find vermiculite or perlite. However, as we are in a region of high volcanic activity, pumice is readily available and cheap. This is the reason why vermiculite or perlite are not used in gardening near me.

QUESTION 1) I have found a source for FOAMGLASS:- FOAMGLAS® HLB 800 insulation - ASTM C552 Grade 8 (https://www.foamglas.com/en-us/produ...cks/hlb-800-us)

Thickness: 2 to 7 in (in 1 inch increments)
Size: 18 in x 24 in
Density: 7.5 lb / ft³

• Can I use this material under the bricks?
• If yes, what thickness should I use?

QUESTION 2) I plan to encase the whole oven inside a red-brick wall. As i cannot find vermiculite or perlite, I plan to cover the oven with ceramic blanket (only) and then fill the walled enclosure with pumice / lime (Lime Concrete)

• What thickness should the ceramic blanket be?

[UtahBeehiver]

FoamGlass will work fine under the oven, min 2" thickness 4 better but depends on how you are going to use the oven. Just having a pizza party, then 2" okay, extended multi-day cooking, then 4" better. The high end temp range for FG 800 is a little over 800F it will be close but I do not see the bottom of the oven floor reaching temps where there is an issue. A layer of CaSi board would be nice but you have to use what ya got. I possible layer could be a pumice/concrete between the bricks and the FoamGlas but not sure what size the pumice particles are and what ratio to cement you would use.

[Dr. Leslie]

Hi Russell,

Very well!!

I have just got back from my foraging and this is what I have.

• RockWool - 2" thick
• FoamGlass 2" thick.

My plan now, going with your flow, is:

• 2" FoamGlass with 2" pumice concrete on top (4" total)
• It seems that the correct proportions for the concrete are : 3 pumice, 1 sand, 1 lime. I will check some more sources.

• I have enough RockWool for 6" of insulation.

[UtahBeehiver]

Rockwool is not the best dome insulation due to the absorbs water readily and compresses easily reducing insulation value. In a previous post you mentioned that ceramic blanket was available from your work, this would be a much better choice.

As far as the pumice/lime concrete mix, the leaner the mix, san the sand, the better the K (or thermal conductivity value, at least for p/vcrete is see attachment) so I would assume the similar with pumice.

[Dr. Leslie]

Hi Russell,

I really do appreciate your comments and your time!


Obviously I have run into problems, which I hope will not be the end of the project!

• When I went to pick up the "ceramic blanket", it turned out to be RockWool. That is why I decided on 6"

• The second point, water absorption, led me to the idea of enclosing the entire oven inside a wall. This will have a roof so I hope that there will be no water incursion!

1. I mixed the concrete: 1 cement ( 30% portland / 70% lime) - 5 pumice - 1 sand. I figured on some sand because the pumice "grains" are a lot larger than vermiculite.

Anyway, I realize that this is all a compromise so I am looking at it as an experiment. At least the brick is real firebrick

[Dr. Leslie]

Hello Russell,

I think that I have found the correct material. Its 2 inches thick so I plan to put on 2 layers = 4"

What do you think?

[Dr. Leslie]

This is 25 sq. Ft.

How much will I need for two layers?

[UtahBeehiver]

Calculate the area a sphere and divide by two. plus a contingency.