Insulation Efficiency

[TDVT]

Thanks Jim. Not having seen the product, I was thinking it was maybe less dense than it actually is.
My inclination is to use a box enclosure around the oven. Have you ever used unfaced fiberglass at the point you would use vermiculite fill (after a hi-temp blanket)?
I think it has better insulating properties & is certainly easy to get.

Ted

[CanuckJim]

Ted,

I have no experience with using fiberglass insulation around an oven. What I normally do is use three inches (five at the apex) of insulating blanket, then a further three (and five) of castable refractory insulator. The product I use for this last is called Matrilite 18, although you could use vermiculite/cement at a ratio of 5:1. After that, you could fill with dry vermic, but I really don't think it's necessary, even in my climate.

Jim

[david s]

I used fibreglass insulation on my first oven. It works ok but compresses easily which made it really hard to get the outer spherical form right. I ended up with only half the intended insulation thickness. I would only use vermiculite again. There is a cloud over the safety of ceramic fibre (carcinogen)

[BCiliberto]

1" insulfrax, 2-4" vermiculite then 9" fiberglas seems to be working real well for me-- no temps taken on exterior of insulation, but if I put the oven "to sleep" at 400, it's 300+ in the morning. under hearth slab is 4" of vermiculite concrete (slab per Alan Scott method, pompeii dome oven per Forno). I may add some fiberglas underneath this winter. Seems to me the key is not to have 1,000 degree brick against the inexpensive fiberglas. But fiberglas is sure a great value compared to alternatives.