What kind of wall gives the higer R value.
Before I get a building permit (France) a report has to be made about insulation and ventilation, the man who is doing the report never did any on a light clay house. In his mind the R value is way lower than straw bale. I googled but did not get an clear comparison I could send him.
Any one an idea where to look?
Light straw is going to have a lower r value at r-18 or r 1.5 per inch. This is because a LSC wall should not be greater than 12" thick or else it may rot.
http://www.greenhomebuilding.com/QandA/cob/strawclay.htm "Depending on how much clay you add and how much you compress it, you could expect an R-value of around 1.5 to 2 per inch of thickness for a light straw clay wall. That compares to almost R-4 per inch of thickness for fiberglass. So you will need twice the thickness of straw-clay as you would fiberglass to reach the same nominal R-value. In fact, however, the straw-clay wall will perform better than would be predicted from this equation, both because of the added thermal mass effect and because the straw-clay fills the cavity more completely than fiberglass batting."
These links and quotes are from Michael Smith's Q/A on greenhomebuilding.com.