Hi all – What are the R-values for compressed earth block (CEB) and rammed earth, respectively? I'm having a heck of a time finding this info on the websites of manufacturers and suppliers. Sorry if it's been covered in other threads – I'm getting errors every time I try the Search function here. Also, I'm eager to hear your thoughts on these methods for home construction in general. I was surprised that there are no dedicated topics for them here like there are for SIPs and ICF. Thanks.

.125 to .25 per inch

Earth and masonry materials normally are able to hold a lot of heat (or cold), which makes them good for thermal mass, but are not considered insulation, because heat (or cold) travels well within them.  The reason you are having trouble finding a published R value is that no one really thinks of them as insulation.