[Cob] Exterior insulation

[raduazo at cox.net]

Jesse,  Ianto is now using a system where he adds two strings to a two string bale, then chainsaws the bales apart to form two thin bales which he uses as a support surface for building cob. I have pictures, but I am no home so I can't send them.
            I am planning on trying a paper/clay system this summer or as soon as the weather gets a little warmer. I will start by soaking bundles of newspaper in a pit for a week or two and then rototilling them into pulp and adding a little clay with my cheap front tine tiller. I will then attempt to build up a 4 inch thick layer of paper/clay on an existing cob wall, possibly using dead-man strips imbedded in the paper/clay.
             The paper/clay will then be given a color finish of some sort perhaps lime putty or a colored paper/clay. I am very fond of a red clay from a friends farm in VA.
Ed
---- Leslie Moyer <Unschooler at atlasok.com> wrote: 
> 
> 
> jwellman at jwgeo.com wrote:
> >    
> >    On a different note, what ideas have people considered for
> >    exterior-to-COB insulation?
> >   
> 
> 
> Jesse,
> 
> I've proposed rockwool (a.k.a. mineral wool), but I know of no one who 
> has used it and I haven't tried it yet.  Rockwool is made of mineral 
> slag (a waste product of the coal-burning power plant industry) and 
> sometimes some added basalt, depending upon the composition of the slag. 
> It is vapor permeable. You can get a high R-value in a fairly thin 
> thickness and my thought is that it could be applied to a cob wall and 
> then plastered over.  I can imagine dipping it in slip, covering both 
> sides, and then "sticking" it to the exterior, finishing with a final 
> plaster on the exterior.  But that's all speculation--I haven't even 
> seen any actual rockwool yet! 
> 
> There are various forms of it....I'm wondering about a semi-rigid sheet. 
> There is a form that comes in fiberglass-like batts, but breathing 
> particles can be dangerous and I can't imagine a way to adhere the batts 
> (they're too flimsy).  I don't know how flexible the sheets are....I've 
> read that they can conform to curves, but I don't know how tight a curve 
> they could handle.  Some brands of rockwool contain formaldehyde, but 
> others don't and are completely inert.
> 
> I've encountered some snobbery about using a manmade material with cob, 
> but it hasn't squelched my interest in it.  In many temperate & colder 
> climates (including most of the US) the embodied energy in insulation 
> can very rapidly offset the energy used to heat or cool a building--and 
> will continue to provide benefit over the life of the building.  And 
> rockwool is mostly (if not totally) a waste product.
> 
> Many different things can be added to a wall cavity to increase 
> insulation--basically building a double-wall--but it sounds like so much 
> extra work & time. 
> 
> Volcanic pumice can be added as an additive to cob, but for much of the 
> world (including where I live) this wouldn't be locally available. 
> 
> I've read about rice hulls in cavity insulation, but does anyone know if 
> it can be used as an additive?  Rice hulls aren't locally available to 
> most places either, but I think I can find a source within a couple 
> hours from here.
> 
> --Leslie
> 
> 
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