[Cob] Re: insulation

[Will Kernan]

I have been experimenting a little with shredded polystyrene added to cob to make it insinuative. Polystyrene is Styrofoam, It is nontoxic, doesn't off-gas, and is thrown away in massive quantities. I have made some test blocks at 1 to 1 and 2 to 1 ratios of cob to Styrofoam. The blocks are very light,  don't burn, and are durable enough to be a wall surface. They aren't as strong  as regular cob. I think the best use is to make the inside of the wall regular cob and the outside foam-cob. polystyrene has a R value of about 4 per inch. the R value of cob is debated but I assume 1 per inch. So at a 1 to 1 ratio you get an R value of 2.5 per inch. In a 12 inch wide wall with the inside 6 inches regular cob and the outside six inches foam-cob the total R value is 21, which is better than a conventional 2x6 wall. In theory anyway. I haven't found a way to quickly shred the foam, a friend is going to loan me a wood chipper to try. I haven't tried to get large quantities of free
 polystyrene, I know there are places that will gladly give away tons but haven't found one locally. And I don't know how easy it is to make large batches of foam-cob. 

			
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