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Old 05-23-2014, 02:37 AM
Apprentice
 
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Default Heat loss through exposed floor at front problem?

Hi folks,

When pouring my vermiculite layer, I left some room at the front for a facade as I didn't want the vermiculite exposed at the front. I was intending to use firebrick (same bricks as for oven floor), to build a decorative facade in front of the vermiculite layer and below the oven opening... the arch would rest partially on this facade...

Now I'm thinking that this would create a thermal path through the floor and down to the hearth bypassing the vermiculite layer... am I over thinking it, or might this be a significant issue?

Thanks in advance.
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Old 05-23-2014, 02:51 AM
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Default Re: Heat loss through exposed floor at front problem?

A photo might help. If your decorative arch is totally separated by say 10 mm this gap can be filled with vermicrete and provides quite a good insulation. I can hold my hand against the outer decorative arch after the oven has been cranking for an hour and a half. It's certainly better than having it connected where you get good conductive heat transfer. Using fire brick for the decorative arch is not a good choice as any smoke staining will be impossible to remove. Glossy tiles are better and will clean off well with some damp newspaper.

Last edited by david s; 05-23-2014 at 02:55 AM.
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Old 05-23-2014, 03:15 AM
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Default Re: Heat loss through exposed floor at front problem?

Thanks David,

I only have the vermi layer down so far.

I was planning to seperate the dome from the entrance - I was more thinking of the fact that the arch will be connected to the floor thermally and the floor is connected thermally to the base via the bricks below the arch.

I've attached a diagram.

Do you think this is a problem?

Edit: update the attached image
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Heat loss through exposed floor at front problem?-arch_floor.jpg  
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Last edited by di11on; 05-23-2014 at 03:19 AM.
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Old 05-23-2014, 03:36 AM
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Default Re: Heat loss through exposed floor at front problem?

No that looks fine to me. I think you are over worrying. You've isolated the dome and floor pretty well. just be careful about drying the vermicrete layer before covering over it and locking in the moisture. Attached is an experiment I did which demonstrates how important this is. Sun and wind can do a lot of the drying for you but you need to give it some time.
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File Type: zip Vermicrete insulating slab copy.doc 3.zip (73.2 KB, 27 views)
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Old 05-23-2014, 05:26 AM
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Default Re: Heat loss through exposed floor at front problem?

You will be fine....My design is very similar and I have not had a problem.
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Old 05-23-2014, 02:04 PM
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Default Re: Heat loss through exposed floor at front problem?

If you re going through to the trouble of creating a heatbreak between the dome and entryway, you may want to slide a few IFB between the floor bricks and entryway bricks. Since they will be in direct contact, there will be some amount of heat transfer to exposed entryway bricks. How negligible this is, I don't know. I did it to be safe. The cost of IFB to to do this would be about $12-15.
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Old 05-23-2014, 02:40 PM
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Default Re: Heat loss through exposed floor at front problem?

Quote:
Originally Posted by GianniFocaccia View Post
If you re going through to the trouble of creating a heatbreak between the dome and entryway, you may want to slide a few IFB between the floor bricks and entryway bricks. Since they will be in direct contact, there will be some amount of heat transfer to exposed entryway bricks. How negligible this is, I don't know. I did it to be safe. The cost of IFB to to do this would be about $12-15.
Thanks Gianni. What are IFB?

Edit: insulating fire bricks I guess ?
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Last edited by di11on; 05-23-2014 at 03:03 PM.
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Old 05-23-2014, 10:55 PM
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Default Re: Heat loss through exposed floor at front problem?

Quote:
Originally Posted by GianniFocaccia View Post
If you re going through to the trouble of creating a heatbreak between the dome and entryway, you may want to slide a few IFB between the floor bricks and entryway bricks. Since they will be in direct contact, there will be some amount of heat transfer to exposed entryway bricks. How negligible this is, I don't know. I did it to be safe. The cost of IFB to to do this would be about $12-15.
The problem with IFB's is that they abrade really easily if they're anywhere exposed to oven tools etc. Some builders cover them with stainless in the area that gets plenty of wear.
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Old 05-24-2014, 06:23 AM
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Default Re: Heat loss through exposed floor at front problem?

I'm thinking, as a compromise, a 10cm gap between oven floor and entry floor filled with ceramic blanket and covered with a thin layer of refractory mortar? If it degrades over time, I just re-mortar it?
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Old 05-24-2014, 08:10 AM
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Default Re: Heat loss through exposed floor at front problem?

My error. I mistakenly assumed there would be some form of entryway cover, like stainless. David's words ring true - any kind of insulation needs to be kept away from abrading tools and pans, but more importantly, away from food.
Mortar would just crumble, and for that matter is not all that healthy to get into your food.

An option would be to taper the matching sides of the adjoining entryway and floor bricks to leave a 1/8" - 1/4" gap at the bottom. The top surfaces would connect tightly, but the taper would create minimum contact between the two.

Another solution (oft scrutinized) to reduce heat transfer contact between floor and entryway is a length of square stainless tubing.

Last edited by GianniFocaccia; 05-24-2014 at 08:12 AM.
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