To keep the oven hot

[eprante]

Re: To keep the oven hot

If the cost of shipping is that high I would go old school and insulate the bottom with Vermicrete. I did that on my oven and (5" thickness) and I get similar heat retention to what Les posted. I think a well insulated door is key. My door is insulated with 2" of the FB blanket and seals very well
Eric

[deejayoh]

Re: To keep the oven hot

The entryway and vent get quite hot near the oven. Especially where the gasses/smoke are coming out of the dome. The reasons you use firebrick in the oven are a) heat retention and b) to prevent bricks spalling (firebrick are more durable in heat/cool cycles than clay brick). The first reason isn't really relevant in the entry arch. It's the builders choice if they want to make the investment in firebrick to reduce the chance of spalling.

My $0.02 is that the entryway takes only a couple dozen bricks. The added cost is so minimal I'd use firebrick. But that is just me.

You don't need a gap between the entryway and the landing. it will just collect ash and dirt, while delivering no benefits in terms of heat retention or cooling.

[DBinnema]

Re: To keep the oven hot

Awesome - I can easily (and now plan to) do that.
I'll leave a 1/4" gap in the floor just in front of where the door will sit. Thinking of switching from the harringbone pattern to just rows of bricks for the entry way. Perhaps I'll leave another 1/4 gap at the very front on the entry way.
So, how hot does the entryway / vent get? (cool enough to allow for the use of regular bricks?)

[Gulf]

Re: To keep the oven hot

"It only takes some spacing between the floor bricks in your oven and the floor bricks in your entry so they do not touch to make a heat break. About 1/8th to 1/4 inch will do. You can place ceramic fiber tape in that divide or just let it fill up with ash " (Gulf)

- Only a space between the floor bricks? Why not the arch?
It would be a lot simpler to just have spacing between the floor bricks...

Yes, on the floor brick, no on the arch brick. Because, the smoke and heat would escape in the space between the arches. Someone else on the forum can attest to that. I am not sure just how much of a problem that would be, but it would at the very least, be un and would probably effect the draw to some point.

[DBinnema]

Re: To keep the oven hot

Yes - it is my location that is to blame.
This oven is costing me roughly three times what it would cost me if I lived somewhere a little more... "beaten". It cost me $400 just to get firebricks sent up here on a barge. I might have thought twice about taking this on had I realized how expensive it would be - but too late now. I suppose there has be SOME downsides to living in paradise.

[deejayoh]

Re: To keep the oven hot

I checked out McGill's Warehouse, and the prices were indeed good , but the shipping was over $300,

Interesting. I just loaded up a cart there with 4 rolls of 1" blanket and 2 pieces of 2" CF Board and the shipping was $122. That seems pretty good to me, doesn't even come close to eating up the savings vs. other suppliers.

Maybe it's because you're in Canada? (and a little off the beaten path)

I see they now also carry diamond saw blades and concrete polishing supplies for good prices. Weird store, but good deals

[DBinnema]

Re: To keep the oven hot

I feel that having decided to add the extra layer of insulation underneath, I can skip the thermal break (unless it is very simple to do) and maybe put some extra effort into having a good door - something that looks to be in my very distant future at this point.

There seem to be mixed opinions about the benefits of a thermal break, but it also seems that regardless of its presence a well-insulated oven can stay hot enough to bake some break on the second day, and even cook something in it on the third. Good enough for me!

[Les]

Re: To keep the oven hot

I'm really not sure how much the heat break offers. I had a post of the temps on the inside and outside of my door and I recall it was a couple hundred degrees delta (can't find the link). I tested this last night, obviously if this were steel my finger would have been toast. Clearly a heat break won't hurt but is it worth the labor?

https://www.youtube.com/edit?video_id=03Pwaf8NlOU&feature=em-upload_owner

[DBinnema]

Re: To keep the oven hot

"It only takes some spacing between the floor bricks in your oven and the floor bricks in your entry so they do not touch to make a heat break. About 1/8th to 1/4 inch will do. You can place ceramic fiber tape in that divide or just let it fill up with ash " (Gulf)

- Only a space between the floor bricks? Why not the arch?
It would be a lot simpler to just have spacing between the floor bricks...

[ncsmoker]

Re: To keep the oven hot

I've always been able to just put the door in and not have an issue, both with the standard door, and the insulated door I built.

Here is a link to gasket material you can use to help, I have it but have yet to put it on. I know there is a mild air leak as some of the embers are still hot the next morning, but never bad enough to cause smoke. Shipping was quite reasonable, I think I paid $7 S/H and I also bought the hi-temp adhesive.

McMaster-Carr

[deejayoh]

Re: To keep the oven hot

I've never had an issue with my oven smoking after the door goes on. There must be an issue with your door seal, where is it leaking from?

between the arch and the top of the door. I don't have a gasket on the door, so the seal is not airtight. Never saw the need for that. Maybe I should if you are saying you can snuff out the fire with no smoke. Seems like the heat would want to expand and push the door out no matter what. Anyway, I live in the city and try to keep the smokey part of the experience as short as possible in consideration of my neighbors/guests.

[ncsmoker]

Re: To keep the oven hot

To have a 950 degree oven, you've got a live fire in there - and once the door goes on it will smoke like crazy. Not really pleasant for guests if the wind is blowing the wrong direction.

I've never had an issue with my oven smoking after the door goes on. There must be an issue with your door seal, where is it leaking from?

[Gulf]

Re: To keep the oven hot

I checked out McGill's Warehouse, and the prices were indeed good , but the shipping was over $300, and I have not yet locating a more local source for calciam silicate board. But, I fiound out I can get Vermiculite at the animal feed store here, "on island", and so decided to pour four inches of vermiclite / concreate, and put the 2" of FB board I have on top of that. Might be nice to get a feel for "vermicrete". It sounds like the extra effort of adding this will be worth it. Thanks for the feedback.

I plan to first build the arch/dome, and put of deciding if and how to do the thermal break transition to the entryway. But, I do need to know if I should put vermicrite and FB board under the entryway area as well as under the oven.

The entryway arch / vent can be built with something other than fire brick, yes?

DBinnema,
Vermicrete will work great for added insulation under the fb board. The entry does not have to be insulated to the same degree as the oven. Though, it does help to insulate under it to the same heighth as that under your oven.

It only takes some spacing between the floor bricks in your oven and the floor bricks in your entry so they do not touch to make a heat break. About 1/8th to 1/4 inch will do. You can place ceramic fiber tape in that divide or just let it fill up with ash .

[GianniFocaccia]

Re: To keep the oven hot

I guess your recent quake was downgraded all the way down from 8.0 to 7.9... Good to hear you weren't evacuated again. We went through a solid week of earthquakes a few months back and sustained minor damage, but the only thing I was worried about was my oven!

If you care to post your oven plans before you really get started (including the base and support stand), please feel free. I wish I had done so in order to gather input on design and construction elements that I would face later on. I admit I went into the construction phase of my oven 'blind', but miraculously came out with a tiny percentage of trade-offs or shortcomings in the final construction.
John

[DBinnema]

Re: To keep the oven hot

Hey John - No impact here from the Little Sitkin earthquake. I hadn't even heard about it before you mentioned it. Too oven focused perhaps. I tend to pay particular attention to quakes since our whole town was evacuated in 2012 after a 7.8 earthquake, and then again a couple months later.

I was hoping that I could get away with an igloo enclosure; I am building the oven under a cover - but it is still exposed to lots of blowing rain.