crazy idea for timberframe insulation

[Thomas-in-Kentucky]

I've used SIPs (walls) and I've used PolyIso sheets (roof and infill walls) to insulate my timberframe house.  I've also used (blue) EPS around the basement walls.

but now I'm starting on the fireplace "structure" which includes, among other things, a wood-fired bread/pizza oven.  To make the pizza oven more efficient, I started looking at adding more insulation around it.  What I found is that some people (building bread ovens) use a mixture of 1 part portland cement to 6 parts perlite in order to create a castable insulation.  So I ran out and bought some perlite, which isn't very expensive, and is sometimes used to fill the cores of cinder blocks to insulate block buildings (like McDonalds' etc.)    Perlite is stable to 1600 degrees F.  Which got me to wondering...  could this "castable mixture" be the basis for a good (fireproof) timberframe infill material?  Stucco would surely bond to it, and depending on the amount of portland cement, it might be strong enough to hold itself (and windows?) in place after curing.  I doubt the forms required to pour it would need to be very strong.

Thoughts?

-Thomas

[Jesse Frank]

I was thinking about using the same thing for my shop, but using sawdust instead of perlite or vermiculite. I was out building a wood fired oven with it today

I've used a similar setup with portland, sand, fireclay and pine straw to make a couple iron smelters that we fired at about 3000f that held up pretty well until the slag ate away at it

I haven't used it to build with, but I think it's a great idea.

[moose]

Lightweight concrete using perlite has been around for some time.  We've used it along with sand as block fill in music practice rooms it deadens sound well.
The perlite folks have done a lot of mixture testing on the performance of various mixtures, check out www.perlite.org.  Here is a link to some of their insulating tests:
http://www.perlite.org/perlite_info/guides/lightweight_insulating_concrete/general/perlite_concrete.pdf

I suspect that developing a structural solution will require a separate integral structural assembly within the wall, the perlite mix won't support much load.
regards

[Griffon]

Theres another product out there which may be similar; expanded (exploded) clay balls. Anyone have a comparison?

[slowzuki]

The problem is its a good insulation compared to concrete, but no where near xps or batts etc.  My boilers refractory is insulated by the stuff.

[Thomas-in-Kentucky]

Thanks for links/advice/experiences!

From the perlite site (.pdf), it looks like you can achieve maybe R-1 or R-2 per inch for a lightweight mixture?  I'm having a hard time interpreting/converting some of their missing units.

-Thomas

[slowzuki]

Straight perlite can achieve those R values if my memory is right but not when mixed into perlite concrete.  So you would have to build a cavity to pour it into because when not in concrete form it won't hold its shape.

[sawdust]

There used to be a product called Duall (sp?) They were sawdust/cement building blocks they were prone to erosion and though they had a decent fire rating were actually poor insulation is thats what you were after. They were used in schools for awhile, absorbed lots of noise unfortunately they were not very student resistant. I am going to try the perlite mix in my foundry, true castable refractory is kink of pricey.

sawdust

[Raider Bill]

Good show on History Channel's Modern Marvels this week about Isulation. They started right out with ICF's. Pretty much went through everything.
The section they did on spray foam, Icyene? was very interesting.
I'm wondering about the cost to do it yourself.