Go Back   Forno Bravo Forum: The Wood-Fired Oven Community > Pizza Oven Design and Installation > Getting Started

Like Tree1Likes

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 08-11-2012, 01:18 PM
Serf
 
Join Date: Mar 2012
Location: Praha, Czech Republic
Posts: 19
Default Retrofitting under floor insulation - insulation thickness and door/dome ratio

Hi All,

I am looking for advice on the thickness of the insulation layer to add under our 4 piece oven floor. Current dimensions are 29cm door height and ~40cm dome height (72.5%). The floor is not insulated at all (the dome of the oven is highly insulated) and I am trying to figure out the optimal thickness of the superisol board to slide in under the floor (within the confines of the dome, which will itself unfortunately sit directly uninsulated on the a 20cm thick concrete slab).

The 40 cm superisol board insulates from 500c to 67c. I would guess that a 50cm (2 inches) board would insulate from 500c to ~50c. If I add in the 5 cm superisol board, my door height would shrink to 24cm and the dome height to 35cm (68.6%). Does that seem like a reasonable approach?

Do I have to leave any expansion room for the superisol board? If not it would seem preferable to jam it in as snugly as possible. The super isol board will have a seam in the middle (dictated by the size of th door opening of the built oven). Thanks in advance.

I would Ike to be able to cook as many pizzas as possible without having to recharge the floor and I'd also like to bake bread at some point.

The backstory:

I went on vacation with my builder building the pizza oven (a modular Zio Ciro 90cm 4 piece round oven kit - http://www.zio-ciro.com/UserFiles/Fi...vesuvio_en.pdf). That was a mistake as it turns out. I had given him both the Rado Hand CD and a pizza oven design book as reference.

In any case, the end result is a built pizza oven with (a) ~6 inches of refractory cement/vermiculite insulation and a ceramic insulating blanket over the *DOME* and (b) the dome and 4 piece oven hearth lying directly on a ~10inch concrete slab. From what I have read, that means that the oven (in its current state) is going to be a beast to fire since the concrete slab will act as a heat sink.

The floor elements can be removed, since they are currently lying directly on the concrete slab. The edges of the floor elements will have to be trimmed to fit back into the dome, but should not be too dramatic. How much space should I leave between the floor pieces edge and the modular dome? Looks like there is nearly 1 cm of space there now.

Appreciate any advice.
Reply With Quote
  #2  
Old 08-11-2012, 04:11 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,878
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

Removing the first floor tile might be quite difficult because as soon as you lift one edge it might lock in on the other edges. You could try drilling three holes in it and insert some masonry anchors so you can keep the tile level while lifting it. Once you have one out the others should be able to be removed easily.You can easily fill the holes in the tile with some refractory mortar (home brew would do)
Reply With Quote
  #3  
Old 08-11-2012, 05:54 PM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

Even though the "edge" of your dome sits directly on the concrete, you will have achieved a pretty high level of insulation.

"If I add in the 5 cm superisol board, my door height would shrink to 24cm and the dome height to 35cm (68.6%)"

You will be getting close to the optimum ratio of 63%. Getting the floor units up and out should be interesting. As David notes, if you tilt them they may jam. Perhaps consider raising the first one up using very long tapered wedges.

Last edited by Neil2; 08-11-2012 at 06:02 PM.
Reply With Quote
  #4  
Old 08-12-2012, 01:08 AM
Serf
 
Join Date: Mar 2012
Location: Praha, Czech Republic
Posts: 19
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

Quote:
Originally Posted by Neil2 View Post
Even though the "edge" of your dome sits directly on the concrete, you will have achieved a pretty high level of insulation.

"If I add in the 5 cm superisol board, my door height would shrink to 24cm and the dome height to 35cm (68.6%)"

You will be getting close to the optimum ratio of 63%. Getting the floor units up and out should be interesting. As David notes, if you tilt them they may jam. Perhaps consider raising the first one up using very long tapered wedges.
Thanks, David & Neil2 for the feedback. I hope the floor tiles will yield to one of those two methods. I'll report on how it goes.

What does the higher percentage ratio mean in terms of oven performance? Thanks.
Reply With Quote
  #5  
Old 08-12-2012, 04:13 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,878
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

What does the higher percentage ratio mean in terms of oven performance? Thanks.[/QUOTE]

If you were able to measure the difference in performance, I doubt whether you'd record any difference. Certainly none that you will notice.Don't worry about it.
Reply With Quote
  #6  
Old 08-12-2012, 07:10 AM
Serf
 
Join Date: Mar 2012
Location: Praha, Czech Republic
Posts: 19
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

Quote:
Originally Posted by david s View Post
If you were able to measure the difference in performance, I doubt whether you'd record any difference. Certainly none that you will notice.Don't worry about it.
Thanks. My door height is 1-2cm too high.

I was able to get the floor tiles out with the help of a crowbar and some long sticks without too much trouble. Now to order the Super Isol board...
Reply With Quote
  #7  
Old 08-12-2012, 05:32 PM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

"What does the higher percentage ratio mean in terms of oven performance?"

The 63% ratio is cited as being optimum for oven efficiency. A slightly higher ratio implies you might use a bit more fuel but will still burn clean. A significantly lower ratio could lead to less complete combustion and possibly a sootier oven.
Reply With Quote
  #8  
Old 08-12-2012, 07:46 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,878
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

If you double the thickness of the insulation ie 100mm you will end up with exactly 63%, still have a good workable door height, a dome that is closer to your pizza and a really well insulated floor.
lwood likes this.
Reply With Quote
  #9  
Old 08-13-2012, 11:13 AM
Serf
 
Join Date: Mar 2012
Location: Praha, Czech Republic
Posts: 19
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

Quote:
Originally Posted by david s View Post
If you double the thickness of the insulation ie 100mm you will end up with exactly 63%, still have a good workable door height, a dome that is closer to your pizza and a really well insulated floor.
Hi David,

Excellent point. What about adding a layer of firebricks under the floor tiles? Seems like 5cm of insulation should be adequate. The floor tiles are only 6cm thick. Adding ~3cm of fire bricks would at least add to the thermal mass for bread and residual heat cooking.

The fire bricks I have seen here are not exactly straight. Can I use sand under the floor tiles for leveling purposes?

Thanks.
Reply With Quote
  #10  
Old 08-13-2012, 02:46 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,878
Default Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio

Yes you could do both those things. Personally I think 60mm is plenty for the floor. 50/50 sand, fire clay is the usual mix for leveling the floor bricks.
Reply With Quote
Reply

Tags
insolation, retrofit insulation, super isol, superisol, under-hearth insulation

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



All times are GMT -7. The time now is 10:49 PM.

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