polyisocyanurate (rigid foam) insulation

[defed]

anyone use this (foil both sides) in their oven?

from what i can tell, it is at least rated to 300F, and has the highest rating of any of the other rigid foam types.

i went to ask my uncle (has a welding shop) how much sheet metal was, and he happens to have a pile of lighter gauge material i can have for nothing. he also has a pile of 2" foil faced foam i can have.

but wondering if it will hold up to 450F. for free, i guess i can test it!

the cost of my oven just dropped w/ these freebies.

[Popeye]

Most foam insulation is combustible and shrinks like crazy when heated.

[defed]

i emailed the mfg to see what they say. i know that the stuff melts/burns under direct flame, just wasnt sure about indirect heat. the 'iso' foam can withstand more heat than the regular polystyrene, but still probably only 300F max.

since the sheets are only 1.5" thickness, and i have 3.5" wall, worse case i will put some 2" high heat insulation on the 'heat' side, and the foam on the outside. i really doubt that 2" mineral wool will be anywhere near 300F on the outside.

[Popeye]

Yep, it's flammable too. It would be interesting to hear what they say about the combustion temperature.. no flame required

[defed]

here is the response from the mfg:

>>>
The working service temperature of Celotex is -15 to + 100 degrees.

If used consistently outside these parameters, the board would start to
degrade.
>>>

i presume it is in degrees C since it is a UK company....which is not even the 300F i had read.

either way, with 2" of mineral wool between it and the heat, it should work as an additional layer of insulation.