ceramic fiber materials

[rwiegand]

Can any of you experts suggest which of the materials offered by this supplier is appropriate and/or similar to the FB products? The cross-country shipping rates are such that a local source would really be appreciated. I don't understand the different chemistries of these materials, nor the industry jargon to interpret what I am seeing.

(I didn't see a rule against posting about other suppliers here, please forgive me if I missed it)

[UtahBeehiver]

There are a lot of different high tech board and blanket out there, basically two types, calcium silica and aluminum silica, you will have to compare the following items to get an apple to apple comparison, Thermal transfer value know as "K" values at a specific temperature, IE Thermogold 12 is a CaSi board with a K value of 0.60 BTU-in/(hr-ft3-F)at 700 F. The second critical item for Ceramic board in compressibility, again Thermogold 12 is 100 psi with 5% compression. I also used FoamGlas(expanded glass foam)as my first layer of insulation since it will not absorb water like CaSi will.

[rwiegand]

Thanks! I ended up with a board called Superwool 607

The thermal conductivity is given as 0.62 BTU•in./hr•ft2•°F at 1000 deg F, compressive strength is 15-25 psi @5% deformation. Since the dome will exert about 1 lb PSI around the rim that should be plenty of margin.

[UtahBeehiver]

I think superwool 607 is a blanket which is good for the dome insulation. IMHO, 15-25 compressive strength is not sufficient for floor insulation, although I showed you Thermogold compressive strength at 100 PSI, FB's AlSi board has a compressive strenght of abt 75 psi.

[rwiegand]

I grabbed the wrong number. The compressive strength for the board (they make both a board and blanket from this material) is actually 55 psi, within a factor of two of the Thermogold. The load of the rim of the fully built dome will be right around 1 psi, a little higher at the bases of the arch. I wouldn't have thought there would be significant danger of crushing it even at the lower value, am I wrong? I don't have experience with this material, only with 10 psi foam loaded to about 5 psi without any significant deformation--but that's a totally different material and the analogy may not work. Is the issue actual deformation potentially leading to a crack, or loss of insulating value due to compression? The latter I could tolerate, since I'm doubling what many people have been successful with, the former not so much.

It's not yet too late for me to take this back and get something else if it has potential for disaster.

[UtahBeehiver]

I can't say whether 55 psi is sufficient or not since I did not use board with this spec. Maybe there are others on the Forum who installed CaSi or AlSi with this compression rating and can comment on if there were any issues. What are the cost differentials between this board and one with a higher compression spec?

[rwiegand]

About $400 less,based on what I've been able to find locally or mail ordering the FB board from California, so a non-trivial difference.