While researching (googling ) on type of "cheap" insulation I'm found a straw clay insulation that has R-20 for 30cm wall (12"). That is VERY impressive, and I only need to have a R-10 insulation. But after my research continued I'm found next article: http://www.foxmaple.com/proclay.html, that describe how to create insulation with wood chips, that will as good, as straw clay.
That is VERY VERY interesting, because in my region there are alot of wood processing factories, so wood chips I can get for FREE!!! in any quantities
But!! (always that "but" )
I can't found any actual scientific (or scientific like) research report on this type of insulation. Can somebody share with me some more info on this subject?
Re the insulative value of this type of wall, since there is no scientific data, lets look at what we do know. Hardwoods have an R value of ~.91 per inch; softwoods ~1.25 per inch. Clay wouldn't have enough R value to even mention here. So, assuming a 12" wall was solid softwood, it would only have an R value of 15. But, the walls we're talking about here are not solid wood.... and they have clay mixed in....so they wouldn't even have an R 15 value.
The real R value of a 12" wood chip wall (some call it chip slip) would likely be more comparable to a standard 2x4 wall insulated with fiberglass (R 11).....and perhaps even less....but, it would depend on the amount of clay, how tightly the mix was compacted, size of chips, etc, etc. My 4" thick wood chip walls (chip slip inside 2x4 studs w/ 1/4" earthen plaster inside & out) feel as though they have very little insulative value.
I believe one could get a higher R value with this type of construction using straw rather than wood chips. How much though I have no idea. It may not be enough to justify the extra trouble and expense being that wood chips are readily available to you.