Starting my build soon - have some insulation questions.

[sharptailhunter]

Howdy!

I'm planning on beginning my build this week and next week. I have the base slab done already. Next, of course, is the stand and hearth slab. I will use ceramic fiber board for the floor insulation. I have read a bunch of posts on here and couldn't really find a definitive answer. I know most people are using 2" of ceramic board in between the oven floor and the structural hearth slab. Because I live in Idaho, and it can get down right cold - and I still want to be able to cook in the colder months - I was initially planning on using 4" of ceramic board instead of 2". Yeah, I have read about insulate, insulate, insulate... and you can never have too much... But, I guess I'm wondering if 2" would work adequately and/or would doubling it not necessarily equate to double the practicality? FWIW, I plan to do a framed enclosure with ceramic blanket followed by loose fill vermiculite. Because of my design idea for that, it would change a little how I did the hearth slab with 2" vs 4". Any thoughts or tips would be much appreciated, thank you :-)

[david s]

Re: Starting my build soon - have some insulation questions.

Your decision. You won't be gaining that much more by doubling it and it is expensive stuff. You could compromise and lay a few inches of vermicrete which is cheap and then the cal sol board.

[Tscarborough]

Re: Starting my build soon - have some insulation questions.

The hearth is the hardest area to get to temp and bleeds the most from the pizza, so it should be the area most insulated.

[texman]

Re: Starting my build soon - have some insulation questions.

i would use a vermicrete layer as said. not only for insulation value, but height. Check your elbow to floor distance and consider what height you want your oven floor to be. I am glad that in my redo i added the height to the oven and have an easy working oven floor that i can see without bending over.

Texman

[vertigopilot]

Re: Starting my build soon - have some insulation questions.

In my latest oven build I used 4" of vermicrete under my 3" hearth slab with firebricks set on edge for a 4.5" hearth. The heat absorption in the hearth is excellent, but the rate of heat loss downward is not as good as I'd prefer.

On my next oven, I'll use an 8" vermicrete layer with 2" of CalSil board on top of that for better heat retention.

[DavidApp]

Re: Starting my build soon - have some insulation questions.

Hello Sharptailhunter

After reviewing a lot of builds and asking almost the same question that you have asked I went with 3" of ceramic fiber board. I would try to get 2" board and 1" board to make the thickness if you can as the board does not seem very accurate in thickness. The more layers the more chance of variation. My board was 1" thick and I had to do a bit of swopping around to even things out.
I did consider Vcrete but decided against it in the end. I did cast 2 Vcrete slabs to go under the entry arch pillars. They were 10" x 9' x 3" and after they had setup for a few days were very solid. I had thought of making a larger tiles of Vcrete to go under the oven but was advised against it because of the strength of the tiles. From what I saw you could probable cast a 18" x18" x 3" or 4" tile and it would hold up well. I did a 5:1 mix.
Lots of decisions to make.

David

[sharptailhunter]

Re: Starting my build soon - have some insulation questions.

Hello All!,

Thank you for everyone's input. This forum is great. It really gives me confidence to attempt a project in the realm of something I've never done before. I'm about to order my insulation board. I'm curious about which product folks recommend purchasing and from where? There is this: McGills Warehouse Online Department Store, has anyone had any experience with it or them? I'm all for supporting James and his products but there is some cost savings to be had with the link I posted. From what I've been able to read about and determine, it's essentially the same stuff, yes-no?
Thank you, Alex

[cook4fun]

Re: Starting my build soon - have some insulation questions.

Texman, I really appreciate your insight with "added the height to the oven and have an easy working oven floor that I can see without bending over"...

I'm planning on having the hearth height at 52 inches ...with the math like this...(hearth thickness @ 2", below that the CALSIL@ 3 inches and below that the firebrick @ 2.5 "), leaving about 44 1/2 inches for the actual concrete structure...this way I can "see" directly into the oven...

All thoughts and experiences welcome !

Thanks !

[mrchipster]

Re: Starting my build soon - have some insulation questions.

I also wish I had more insulation in my floor. I believe I lose most of my heat via the floor as I read elevated temps in the top of my storage area under the oven and the flor of the oven inside is often 50 to 100 degrees lower than the dome temp a day or two after a fire up.