Insulation Efficiency

[dimitrisbizakis]

Re: Insulation Efficiency

Some advantages of the loose perlite is that it was cheap and would uniformly cover the oven. FB Blanket has come down in cost, it is used extensivly for industrial use and is an excellent insulation. If you are able to insure that the dome is fully wrapped with the blanket, it will hold the heat in really well. I built my oven out of fire brick and used vermiculite and perlite, but I believe the premanufactured ovens that Forno Bravo are selling, now only come with FB Blanket insulation. You will be fine with 3" of FB Blanket.

I don't know why but now an 100 lt perlite costs 8 euros, i will need about 10 so 80 euros.
I have found an 610X9000 mm 25 mm Ceramic blanket for 30 euro, i think that it will cover the dome (90 cm diameter and 45 cm height) for once.
I'm thinking to buy 2 rolls and make a 2 layer insulation.
The only thing i'm troubled with is the final closer but i think i will go for a house.
How can i calculate the exact m3 of perlite i will need for a loose 10 cm?

[Spunkoid]

Re: Insulation Efficiency

Some advantages of the loose perlite is that it was cheap and would uniformly cover the oven. FB Blanket has come down in cost, it is used extensivly for industrial use and is an excellent insulation. If you are able to insure that the dome is fully wrapped with the blanket, it will hold the heat in really well. I built my oven out of fire brick and used vermiculite and perlite, but I believe the premanufactured ovens that Forno Bravo are selling, now only come with FB Blanket insulation. You will be fine with 3" of FB Blanket.

[dimitrisbizakis]

Re: Insulation Efficiency

Hi everyone, instead of 1" FB blanket and 4" loose perlite can i use 3" of FB blanket only?

[BobGer]

Re: Insulation Efficiency

Have no idea what burned rice husk ash would do; glass would seem to offer zero insulation. You can order the high temperature insulation blanket - look on the internet for sources including forno-bravo. Most, if not all of it is manufactured in China anyway. And not sure why pearlite or vermiculite isn't also available worldwide. Regardless, I wouldn't sacrifice insulation which is the key to the whole idea of an outdoor oven. Good luck.

[Hendrikwal]

Re: Insulation Efficiency

Hi there, im building a oven in vietnam and we not have any fancy blankets and stuff like this around hee since there is no use for keeping things warm,... Its warm here all day haha.
But i was thinking of putting a 3 inch layer of burned rice husk ash on top of the dome and then cover it with a 2 inch layer of concrete mixed up with the same stuff.
Whats yr idea about this? An other option was braking a whole lot of glass up and stuff that between the inner and outer wall of the dome?
Thaks for yr toughts.
Hendrik

[gdest]

Re: Insulation Efficiency

I agree you want the insulation first. You want to heat up the oven not the concrete mass.

[BobGer]

Re: Insulation Efficiency

Appreciate the quick response and advice from both VTSteve and Ken524. It never was clear why some designs called for the aluminum foil. One less step!

[Ken524]

Re: Insulation Efficiency

on top of firebrick, which I was going to cover with high temp mortar

You really don't need this. If you built a Pompeii, there is plenty of thermal mass in the bricks. No need to add more... unless you really want to. Some add it for structural integrity.

I was going to then cover with aluminum foil

You REALLY don't want/need aluminum foil. It does absolutely nothing and will eventually corrode away.

then the FB blanket (3 inches),

Yes!

then a layer or two of vermiculite concrete

I did this as well. I think it's worth while. Can't have too much insulation.

And as Steve stated, you want the most efficient insulation (fire blanket) closest to the heat.

[vtsteve]

Re: Insulation Efficiency

Put the blanket on first. You want your most efficient insulation closest to the hot zone of the oven.

[BobGer]

Re: Insulation Efficiency

Likely covered in previous posts, but haven't found it - question about the order of layers: on top of firebrick, which I was going to cover with high temp mortar, I was going to then cover with aluminum foil, then the FB blanket (3 inches), then a layer or two of vermiculite concrete, then a final coat of some waterproof stucco. So my question is whether putting the blanket first is appropriate or is it advisable to first put the vermiculite/concrete down? Or does it not matter? Thanks

[alex.g]

Re: Insulation Efficiency

The way you have it there is no adhesion between the blocks and the concrete due to the rubber matting, plus when it rains the water will sit on the rubber matting and travel up the blockwork into the oven.
I can see in the pic that moisture is already travelling up the blockwork.

Any dampcourse should be well above ground level to stop this from happening..

bottom will be covered by rubber matting inside and outside, so there will be no water coming into foamblocks. Will post update

[david s]

Re: Insulation Efficiency

Ceramic fibre blanket is made from fibres that are made of clay.

[v12spirit]

Re: Insulation Efficiency

"Rockwool" is a term we don't use in the US. If it's domestic insulation, like fiberglass, it may have organic binders that will burn and stink at the right-next-to-the-dome temperatures. Before you get too far, heat up your kitchen oven to 550 degrees f. (288 degrees c.) put a chunk of the rockwool in, and see if it stinks up the place.

If it's a refractory insulation, you should be good to go.

Rockwool is an alternative to mineral wool which is a lightweight fibrous material made from slag or glass. What is the difference between this and ceramic planket insulation?

[brickie in oz]

Re: Insulation Efficiency

Cement rich concrete should by itself be waterproof, you can also add a chemical waterproofing agent to the concrete which would probably be a better option.

My first suggestion was more for brickwork.

[vtsteve]

Re: Insulation Efficiency

Thanks for the pictures - I guess Google was just showing me the repair/retrofit version. So, for the usual filled-core stand, you'd have to put down at least one course (~200mm) of block, fill and rebar the cores, put the membrane down (with the rebar punched through and possibly sealed), and add courses to reach your finish height. Have I got it right?