Insulation materials Pros cons types and thicknesses

[Wineman73]

I have been reading tons of information on insulating materials on this website and others. Refractory insulated firebrick, ceramic fiber blankets, boards, Vermicrete. I still don't know what performs better than others. The advantages and disadvantages of each material, and what performs better at a lesser thickness. I believe that at some point to much insulation is worthless, over kill, and not beneficent. Would be nice if there is a thermal engineer who can throw some light onto this. I mean I don't want to spend tons of money to insulated my oven with 5 inches of material if i can get away with using 2" of the same material. I believe that there has to be a breaking point.I am also going to try to contact some thermal engineers and discuss these issues further.
thanks

[Paul_H]

Re: Insulation materials Pros cons types and thicknesses

It's important to realize that there really are two distinct parts of a WFO. The firebrick is not an insulating layer, it is a thermal mass. The fire heats up that mass and it is a combination of the hot firebricks and the fire that cooks the food. The insulating layer(s) allow the fire to get the firebricks hot enough to cook a pizza, and also allow the bricks to retain heat for cooking bread, roasts etc when the fire is out.

The ceramic fiber blankets, boards, vermicrete etc all work as insulators that can handle the high heat of the oven without breaking down or combusting. All of them when used in the proper specified thickness will work fine. The reason various materials are and have been used comes down to what materials are available in your location, how easy or difficult they are to use, their cost and what the final structure you plan to build over the oven consists of. Fiber blankets have the advantage of allowing some expansion of the fire brick dome vs. using vermicrete which will almost assuredly crack.

It's a lot of labor to build an oven so you should stick with materials that will give you the performance you are after. Thinking that the standard designs are over insulated and using less insulation than specified many result in an oven that won't get hot enough for your use, or which will cool down too quickly for your use.

Personally I plan on building a vermiculate slab as the base, firebrick floor and dome and toppig it with 4" of fiber blanket.

[Greenman]

Re: Insulation materials Pros cons types and thicknesses

The bottom line is that the better insulated/isolated the hearth and dome are the better it will hold the heat. I built the hearth on 4" of vermicrete and insulated it with 2" of ceramic fibre with a further 2" of vermicrete on top of that. That was then rendered. Vermicrete is cheaper than ceramic fibre or boards but you need to use more of it to get the same result.

I am happy with the performance of mine and it is cooking casserole this afternoon on the retained heat from last nights pizza and it will still be warm tomorrow.

The one piece of wisdom that keeps on being passed on here is that there is no such thing as too much insulation.

I guess it depends on what and how you intend to use your oven but given the amount of work in building one it makes good sense to have it end up as versatile as possible first time around.

Good luck with sorting through the information and I am sure that you will end up with a very satisfactory oven with the benefit of it.

[stonecutter]

Re: Insulation materials Pros cons types and thicknesses

Use what you can get and/or afford, and use plenty of it.