Insulation: The more the merrier. But how much more?

[V-wiz]

So im slowly getting ready to pick up rolls of Ceramic fiber insulation for my igloo style oven. I am going to install as much insulation as needed and skip V-Crete. I understand that CF blanket is more efficient than V-Crete and i just don't want to deal with V-Crete. I have a game plan for shaping the dome so im not worried about the shape. What i am concerned about is the overall bulk of the dome. I don't want to have a "fat-head" dome. So how many inches of insulation would you guys recommend i use?

Thanks for your help.

[azatty]

Re: Insulation: The more the merrier. But how much more?

So how many inches of insulation would you guys recommend i use?

Three inches is the standard for ceramic blanket. There's a thread kicking around the board concerning diminishing returns of insulation, but I don't recall where it is.

[irelande5]

Re: Insulation: The more the merrier. But how much more?

I went 3 " of blanket, then topped that with 3" of vermic-crete, what I found in research from other member and posts was that obvious heat loss is realized more at top, and more is truly better in this instance. I had no trouble with blanket compressing, actually the vermic was so light it helped shelter it and really helped dome final shape. I have a make shift metal door, not nearly tight nor is in insulated, working on that now, and given that i reach working temps of 950 plus, the next day its around 400-500, day after that still in 250 range. good luck!

[deejayoh]

Re: Insulation: The more the merrier. But how much more?

three to four inches of CF blanket is plenty

to irelande's post, I think that it is better to invest in a good door and a heat break than to add insulation beyond that. It is $50 a roll or something like that, after all...

[V-wiz]

Re: Insulation: The more the merrier. But how much more?

Thanks for the respond all. 3" is assuming that vermiculite will be used right? since im not planning on using Vcrete i should technically be using more CF insulation right? about 4-5 inches worth? Thanks again.

[brickie in oz]

Re: Insulation: The more the merrier. But how much more?

i should technically be using more CF insulation right?

Wrong.
CF has more insulating properties that vermiculite.

[V-wiz]

Re: Insulation: The more the merrier. But how much more?

Wrong.
CF has more insulating properties that vermiculite.

Right, im aware of that as i pointed that in my OP, but would 3 inches still be enough?

[brickie in oz]

Re: Insulation: The more the merrier. But how much more?

Right, im aware of that as i pointed that in my OP, but would 3 inches still be enough?

If you lived in the Arctic that would be more than enough.

Edit:
I just saw that you live in LA, 3" is way too much, how cold does it get there?

[V-wiz]

Re: Insulation: The more the merrier. But how much more?

Coldest it would get is probably 37F

[deejayoh]

Re: Insulation: The more the merrier. But how much more?

Right, im aware of that as i pointed that in my OP, but would 3 inches still be enough?

I agree with brickie. That's enough by itself w/o any vermiculite.

[V-wiz]

Re: Insulation: The more the merrier. But how much more?

Ok thanks guys. I trust you all

[Bacterium]

Re: Insulation: The more the merrier. But how much more?

That's why the mantra is
Insulate......insulate......insulate

Isn't the thermal.equivalent of blanket same as 2layers of vermicrete?
Obviously cost and how much space you have around your build are the other 2 things (thermal efficiency is the first) that drive your decision process. For example with my build I want to fit a bar fridge underneath so the equivalent in vermicrete puts the oven floor to high so calsil was my best option to keep the floor thickness down.

[Laurentius]

Re: Insulation: The more the merrier. But how much more?

Ok thanks guys. I trust you all

DON'T!!!!!!! Never all.

[V-wiz]

Re: Insulation: The more the merrier. But how much more?

That's why the mantra is
Insulate......insulate......insulate

Isn't the thermal.equivalent of blanket same as 2layers of vermicrete?
Obviously cost and how much space you have around your build are the other 2 things (thermal efficiency is the first) that drive your decision process. For example with my build I want to fit a bar fridge underneath so the equivalent in vermicrete puts the oven floor to high so calsil was my best option to keep the floor thickness down.

Not worried about space, or cost. As there is a local supplier that sells the CF blanket for $25 for a 25 square foot roll.

[Aegis]

Re: Insulation: The more the merrier. But how much more?

Insulation - Stuff put between spaces of two different temperatures so they equalize out at a slower than natural rate. Ok short version, when it come to keeping heat in an area for extended periods of time...there is no such thing as over insulating - period. Now taking into account cost verses return on investment, you can argue this based on your budget, or lack of one.
Things to keep in the back of your thought process:
1) Heat retention versus cost of materials. If 2" blanket losses 15 degrees per hour and costs 100.00 usd and 4" blanket losses 10 degrees per hour and costs 200.00 usd Then looking at cost per degree savings 2" is more cost effective. Now add in the cost of wood raise the temp to cooking and the length of time you will cook. If you want to cook for three or four days then the extra insulation will save you from building additional fires (wood costs) If you have unlimited free wood, take that into account, but your time to tend the fire is also a consideration.
Where you live is almost meaningless in this consideration for ambient temps pale to oven temps. If you have ambient temp outside of 20 versus 80 degrees the oven is at 900 degrees. the difference is small and not worth looking at for savings. The thermal transfer from 900 to 80 is a difference of 820 degrees versus a difference of 880 or approx. 5% no worries here for sure. Insulate for the 800+ degree difference and disregard the added or subtracted 60 degrees. Also if cooking things for any length of time you want the temp to be stable. (losing less than 8 degrees per hour) Such as pulled pork slow cooking for 14 to 18 hours! Mmmmmmmmmmmm
Also remember your oven is designed to last several lifetimes, cost of insulation spread out over 70 years is usually a pretty small number. If you are just cooking pizzas, no insulation is a good way to go!
Good Luck!