Floor insulation options because of a lack of materials

[Joaam]

Hello great community, this is my first post in this forum, I apologize because I'm not sure if this question has already been asked and answered, I did read several threads with similar topics but couldn't find an answer that was conclusive to my concern, this are my facts :
- I'm building a 40" Corner oven on a second floor of an open area.
- I managed to find in my country "Honduras, Central America" the Firebrick's, Mortar, refractory cement and the blanket but had no luck with the Board and the vermiculite or perlite.

I'm concerned about the insulation in the floor because of the lack of board and/or Vermiculite-Perlite, so mi question is about which other options do I have, I was thinking about 3 :
1) Make a Pour on the floor with a 2" or 3" layer of refractory cement above the concrete base.
2) Place over the concrete base a 2" or 3" layer of the ceramic blanket and a thin 1" layer of refractory cement.
3) Place over the concrete base a 2" or 3" layer of the ceramic blanket and cover it with sand.
Please advise me if any of this options are not adequate and if there are any other option given the limited materials I have.

Thanks a lot for your answers and your great, great forum.

[texassourdough]

I think it is worth noting that many ancient WFOS are very poorly insulated. Better insulated is good, but the impact of less insulation lies mainly in having to fire longer and recharge more often. Insulation is also more important for bread baking than for pizza though it is nice to not have to recharge the hearth all the time.

I have concerns for the integrity of the subhearth blanket over time. Either being crushed or having the sand fill the air spaces such that its insulation integrity is compromised over time. I am trying to figure out how to keep the sand out of the blanket and to create enough strength to support the hearth.... While I am not a big fan of iron in an oven, in this case it should work... How about putting some firebricks on your "floor" to support an iron plate. I would do this within what will be the dome. Then put the blanket(s) in and cover with an iron plate. Then use sand or refractory cement to create a floor mass and cover with conventional fire brick (or if you can't get fire brick, refractory cement).

Good luck! (Where are you located in Honduras. I have been to Tegucigalpa!)
Jay

[Joaam]

Thank you texassourdough for your answer, actually I live in Tegucigalpa, so is nice to hear you've been around.
I haven't thought about the iron but i might try to figure out the way to use it in this particular application.
As for the Sand I think maybe you're right and the contact with the blanket could affect the integrity of the insulation.

Thanks for the advise

[wotavidone]

Hi, there is another alternative if you really want an insulated base. How is the Honduras off for volcanos? Can you get scoria, the volcanic rock that is aerated? Do a google search on it. Concretes made with scoria, sand and cement have insulating properies. Os pumice, the rock that is so aerated that it floats in water?
Regards,
Mick

[Joaam]

Hi Wotavidone, we call that kind of stone "Piedra Pome" in spanish, we really don't have any volcanoes in Honduras but there are many in the countries nearby in Central America like (Guatemala, El Salvador, Nicaragua and Costa Rica) and I think we can find it in the local market.
Is there any particular way (Amounts and method) to make this "Piedra Pome Mix" with cement.? and How much insulation you think this may give in a 2" or 3" Layer?.
Thanks a lot for your answer.

[texassourdough]

Hi Joaam!

The lava is a good idea. The goal is air pockets. A "matrix" of aerated lava and refractory will work. You probably want at least two inches of refractory on top to create mass for heating (and firebrick or another inch/inch and a half of refractory cement. Mass is important - but you don't want heat leaking to the world...any more than you have to!

Good Luck!
Jay

[Lburou]

Hello Joaam

You may get lucky and find a concrete block supplier who can supply you with insulation to pour into the voids of the blocks, providing insulation for filling the cavities in a block wall. That insulation will very likely be vermiculite. I bought my vermiculite from a concrete block supplier. Its worth another search, good luck.

Best Regards,

P.S. The vermiculite based product I used was Zonolite, (Masonry Insulation for block walls and cavity fills).

[Joaam]

Thanks Lburou for your Advice, I'll try that approach also and will contact block suppliers to ask if they have any material for insulation that can be used in the cavities of the blocks.

Best regards
Joaam

[brickie in oz]

You can use aerated blocks for the under floor if you can find them.

Google

[Cheesesteak]

I would say to consider using sand. I've read some say that sand is a poor insulator - but that's simply not so - so long as the sand stays dry.

Some things to consider:
Sand has an approximate thermal conductivity (K value) of around 0.17 (depending on type of sand), which means it is a very poor conductor and a reasonable insulator.

Wet sand, however, is a very good conductor, with a K value of 1.25, which means it's (wet sand) not a good insulator.

Volcanic Rock (tuff) has a K value of anywhere from 0.5 - 2.5 - which means it's not as good of an insulator as sand.

Compare that to fiber insulating boards which usually have a K value of around 0.04 . . . .

That should give you some comparison.

NOTE: K-value is a measure of heat conductivity of a particular material. Specifically, it is the measure of the amount of heat, in BTUs per hour, that will be transmitted through one square foot of material that is one inch thick to cause a temperature change of one degree Fahrenheit from one side of the material to the other. The lower the K-value for a material, the better it insulates. If the K-value of the material is known, the R-value per inch can be determined by dividing 1 by the K-value (R-value per inch = 1/K value). The LOWER a K-Value, the better its performance as an insulator.