Adding Hearth Insulation

[Xabia Jim]

I found that my hearth could use additional insulation. ....something that may be difficult after installation.

I was able to use clay building tiles (flat ones) to put a shelf under my hearth and then stuff insulation into that opening, This gave me an extra 6 inches or so of insulation and me thinks it makes a big diference keeping the hearth hot.

So, fyi it can be done.

[arevalo53anos]

Re: Adding Hearth Insulation

XJ:

A simples layer of 2+ inches of vermiculite/cement or, even better, a couple of sheets of ceramic blankets will do the work without the need of the tiles.
Both the blanket and the vermiculite can be maintained in place just using a thin wooden table (higher temperatures over there will be below the 50?C)

Luis

[gjbingham]

Re: Adding Hearth Insulation

XJ,
Do you have any pics of that fix? I think I understand, maybe. I've got to check under my hearth slab next time I cook. I'm still not happy with the way the floor of the oven is retaining heat.
George

[CanuckJim]

Re: Adding Hearth Insulation

XJ,

On my to do list in warmer weather is to attach SuperIsol panels underneath my oven. Glue won't hold them there, so I'm thinking a few pieces of steel studding and tapcons will work.

Jim

[Xabia Jim]

Re: Adding Hearth Insulation

George I don't have any useful pictures. Basically the tiles formed a shelf in the opening under my oven, then I rammed in insulation so it packed tightly. Cemented in the front and that completed the fix.

The tile shelf still get's warm which tells me that the insulation layer is holding more heat and the hearth should be warmer and hold it longer.

[Xabia Jim]

Re: Adding Hearth Insulation

And, I'd definately agree that putting a high tech material under there and holding it in place somehow would probably be more efficient. I think I did my fix for less than $10 though. (my labor is free)

[gjbingham]

Re: Adding Hearth Insulation

XJ,
You work for wine - not free, unless you make it yourself.

Thanks for the explaination. I'll check mine tomorrow when I fire the oven up again.
G.

[gjbingham]

Re: Adding Hearth Insulation

BTW, I'm starting to think that 6 inches of vermiculite under the dome is probably a better number to shoot for, huh? It seems to me that if you're loosing heat into the hearth, you're basically trying to heat the entire hearth slab. Would insulation under the slab help the situation?

[Frances]

Re: Adding Hearth Insulation

Good question George, that's what I was wondering, too.

On a similar quest I was wondering whether adding another layer of bricks to the bottom of the oven might be worth trying. My baking is going well, but it does strike me that it could be better with more floor heat. Any advice for this??

[gjbingham]

Re: Adding Hearth Insulation

Bricks underneath would certainly increase the mass, and might make you use more firewood to get the oven hot if your insulation is a bit thin. Good question! Whether or not it will prolong the heat of the oven....I guess it's conceivable. My gut is still telling me that without sufficient insulation under the oven floor, you're basically trying to heat the entire hearth slab, which is going to continue to suck heat away from the oven floor.

Frances, have you felt under your hearth for warmth?

[Xabia Jim]

Re: Adding Hearth Insulation

If memory serves me well, insulation is better than thermal mass, particularly for the pizza oven. I think it's good to have some thermal mass to hold heat, particularly for the baker. But certainly it seems you can have too much mass to heat up and thus the insulation layers. A careful balancing act.

Francis, are you talking about putting bricks on top of your hearth? You could probably do a test by just loose fitting in as many bricks as possible then. I've got to believe that heating up another layer of bricks will increase your thermal mass for baking. And how long does the fire burn to season your oven before baking?

6" of vermiculite under the dome... it seems you can't have too much insulation....how much would be too much?

[Frances]

Re: Adding Hearth Insulation

Too much? I dunno, so the oven is too high to cook in maybe Like the princess and the pea, you'd have to use a ladder to get up to the entrance...

I think I've got about 6" of vermiculite under the dome, and the roof of the wood storage area doesn't get warm, or if so only slightly.

Baking for me is usually after making Pizzas, so heat up time (including the pizza bake) is around two hours, close the door, and put in the bread another two hours later - give of take an hour or so, and depending on when the dough has risen. Its never a very exact science for me, I'm afraid...

And as I say, its working very well, we have lots of fresh bread that everyone in the family likes to eat (and thats a seven day wonder all in itself!)

Bit I think I'll try putting some bricks on the floor sometime to see what happens. I'll let you know what happens. Afterall I can always take them out again...

[Xabia Jim]

Re: Adding Hearth Insulation

You could just use high heels princess.

[gjbingham]

Re: Adding Hearth Insulation

George reporting: I cooked pizza's (poorly) tonight. Ambient temperature was around 60 degrees. I checked the underside of the slab's temp: 62 degrees F. Outside the stucco: 59 degrees. Conclusion: Four inches of vermiculite is or may be enough, or at least the heat the heat from the oven is not making it all the way to the bottom of the slab enough to pursue insulation underneath.

On the down side, I stoked the fire big time tonight and put a crack right through the top of my decorative arch. I hardly gave it a second thought.

[Frances]

Re: Adding Hearth Insulation

Hey, watch out or we'll get to where we brag about the size of our cracks...

"Mine's bigger than yours!"