Go Back   Forno Bravo Forum: The Wood-Fired Oven Community > Good Background Information > Newbie Forum

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 05-06-2008, 07:06 AM
dvonk's Avatar
Apprentice
 
Join Date: Mar 2008
Location: Moscow
Posts: 101
Default I know this question is stupid - insulation under

I wonder (surfing brick oven sites) why Alan Scott's following (and probably Alan by himself) pour the insulation hearth under the structural but not vice a versa?
What a thermal mass and what a firing it should be (even despite the fact they put a floor bricks in the side!)???

Last edited by dvonk; 05-06-2008 at 07:17 AM.
Reply With Quote
  #2  
Old 05-06-2008, 09:13 AM
gjbingham's Avatar
Il Pizzaiolo
 
Join Date: Sep 2007
Location: Longview, WA
Posts: 2,021
Default Re: I know this question is stupid - insulation under

I assume to increase the heat retention of the bread oven. Good for baking multiple loads of bread. Bad for pizza - it takes way more fuel to get up to pizza temps. I think in the book, The Bread Builders, the plans don't even show insulation under the hearth.
__________________
GJBingham
-----------------------------------
Everyone makes mistakes. The trick is to make mistakes when nobody is looking.

-
Reply With Quote
  #3  
Old 05-06-2008, 10:35 AM
Frances's Avatar
Il Pizzaiolo
 
Join Date: Aug 2007
Location: Allschwil, Switzerland
Posts: 2,186
Default Re: I know this question is stupid - insulation under

The FB plans had the hearth that way round at first - or so I'm told, bit before my time really. The heat loss through the floor proved to be too great though.

I'd think that would be the same for a high mass oven though too, that it'd work better with insulation all round the outside of the heating mass...
Reply With Quote
  #4  
Old 05-06-2008, 09:36 PM
dvonk's Avatar
Apprentice
 
Join Date: Mar 2008
Location: Moscow
Posts: 101
Default Re: I know this question is stupid - insulation under

But most of them are using it for cooking real small batches of pizza and family-size amount of bread - not like pro using it at all. And I've seen many times words like "when oven cooled slightly, we bake blah-blah-blah" - so, after 1.5-2 of firing, floor still transfuse heat to the hearth.
Reply With Quote
  #5  
Old 05-06-2008, 09:37 PM
dvonk's Avatar
Apprentice
 
Join Date: Mar 2008
Location: Moscow
Posts: 101
Default Re: I know this question is stupid - insulation under

Well, it's clear that increasing of thermal mass will be huge, but how good it for home baking?
Reply With Quote
  #6  
Old 05-07-2008, 05:06 AM
Dutchoven's Avatar
Master Builder
 
Join Date: Apr 2007
Location: Mississippi
Posts: 931
Default Re: I know this question is stupid - insulation under

I think sometimes his plans actually have the insulating hearth floating or hanging on the block walls...there is a oven build site brickoventampa or something...his oven did not have a structural layer of concrete under the oven itself.
My oven was done in that way and I can say it rather stinks sometimes!
Dutch

Quote:
Originally Posted by dvonk View Post
I wonder (surfing brick oven sites) why Alan Scott's following (and probably Alan by himself) pour the insulation hearth under the structural but not vice a versa?
What a thermal mass and what a firing it should be (even despite the fact they put a floor bricks in the side!)???
__________________
"Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity. " Charles Mingus
"Build at least two brick ovens...one to make all the mistakes on and the other to be just like you dreamed of!" Dutch
Reply With Quote
  #7  
Old 05-07-2008, 05:15 AM
dvonk's Avatar
Apprentice
 
Join Date: Mar 2008
Location: Moscow
Posts: 101
Default Re: I know this question is stupid - insulation under

Quote:
Originally Posted by Dutchoven View Post
I think sometimes his plans actually have the insulating hearth floating or hanging on the block walls
They do have, indeed!

Woodfiredpizza.org - Pizza Oven Construction
Wood Fired Brick Oven Tampa October 2004
Reply With Quote
  #8  
Old 05-07-2008, 08:54 AM
Peasant
 
Join Date: Apr 2008
Location: Sioux Falls, South Dakota
Posts: 28
Default Re: I know this question is stupid - insulation under

I don't think I understand the practice of insulating the concrete slab on the foundation. The insulation around the oven walls is necessary for heat retention and structural preservation. But does the insulation under the foundation keep the oven level? Or keep the slab from cracking? Any heaving would crack the foundation with the insulation.
My brother-in-law is working with his town government installing fire hydrants. He was saying from this winter the frost line would be closer to 60"-72". With this factored into the equation, what does the insulation do? Does it keep the ground inside the foundation from freezing?
__________________
Orrin Dean

Excuse me. I'm new at this.
Reply With Quote
  #9  
Old 05-07-2008, 09:36 AM
james's Avatar
Brick Oven Merchant
 
Join Date: Mar 2005
Location: Pebble Beach, CA
Posts: 4,648
Default Re: I know this question is stupid - insulation under

Quote:
Originally Posted by dvonk View Post
I wonder (surfing brick oven sites) why Alan Scott's following (and probably Alan by himself) pour the insulation hearth under the structural but not vice a versa?
What a thermal mass and what a firing it should be (even despite the fact they put a floor bricks in the side!)???
The only reason to build up that much mass in the oven floor is for a commercial bread bakery. I've said many times that the Bread Builder's oven is basically a shrunk commercial bread oven -- where the definition of "commercial" means that it is designed to bake 3-4 full batches of bread from a single firing. That is hundreds of loaves of bread from multiple hour firings.

My cooking floor on my Scott oven was about 9" -- 4 1/2" of brick and 4 1/2" of concrete. A residential pizza oven floor is 2"-3" and a commercial pizza oven floor is 4".

The 9" floor is a real no-no for a pizza oven. Hands-on experience taught me that it is pretty much impossible to keep the cooking floor at high temperature -- because the heat of the fire is wicked away from the inside of the oven to the outer edges of the 9" thermal mass. The Scott design is basically a whoops -- don't do this at home.

Here is a graphic of draw a while back that tries to capture this visually.

James
Attached Thumbnails
I know this question is stupid - insulation under-holding_heat.jpg  
__________________

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

Last edited by james; 05-07-2008 at 09:41 AM.
Reply With Quote
  #10  
Old 05-07-2008, 12:19 PM
dmun's Avatar
Moderator
 
Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: I know this question is stupid - insulation under

Quote:
Originally Posted by Orrin Dean View Post
I don't think I understand the practice of insulating the concrete slab on the foundation. The insulation around the oven walls is necessary for heat retention and structural preservation. But does the insulation under the foundation keep the oven level? Or keep the slab from cracking? Any heaving would crack the foundation with the insulation.
My brother-in-law is working with his town government installing fire hydrants. He was saying from this winter the frost line would be closer to 60"-72". With this factored into the equation, what does the insulation do? Does it keep the ground inside the foundation from freezing?
I think we have two different questions going on here. Orrin seems to be asking about a anti-frost foundation using insulation board as shown in this link:

ESB: Frost-Protected Shallow Foundations

It sounds interesting, but I don't think anyone here has tried this technique yet, and can speak from experience. So I think the short answer is, I don't understand it either. I can see where a heated building would use the heat from the building to keep the foundations from freezing, but I don't understand how it works with unheated structures.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Insulation Blanket Question NanyukiTom Newbie Forum 5 12-31-2007 09:45 PM
Stupid floor question? rwiggim Pompeii Oven Construction 5 07-21-2007 10:21 AM
Insulation Question waitingtocook Getting Started 2 02-20-2007 04:01 PM
insulation question? tommy5 Modular Refractory Oven Installation 5 11-21-2006 12:37 AM
Insulation question sonomacast Newbie Forum 2 08-11-2006 11:43 PM


All times are GMT -7. The time now is 03:08 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC