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indiebands 08-11-2012 12:18 PM

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.

david s 08-11-2012 03:11 PM

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)

Neil2 08-11-2012 04:54 PM

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.

indiebands 08-12-2012 12:08 AM

Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio
 
Quote:

Originally Posted by Neil2 (Post 136493)
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.

david s 08-12-2012 03:13 AM

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.

indiebands 08-12-2012 06:10 AM

Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio
 
Quote:

Originally Posted by david s (Post 136522)
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...

Neil2 08-12-2012 04:32 PM

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.

david s 08-12-2012 06:46 PM

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.

indiebands 08-13-2012 10:13 AM

Re: Retrofitting under floor insulation - insulation thickness and door/dome ratio
 
Quote:

Originally Posted by david s (Post 136554)
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.

david s 08-13-2012 01:46 PM

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.


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