Sheeps wool is the best material for insulating a van, it is the most environmentally friendly as well as providing many other benefits. In this DYI series on converting a van into a camper, rv, or adventure mobile I will discuss why I think Sheeps wool is the best option while also discussing other popular materials(3M Thinsulate or sprayfoam).
I live in Europe and I was only able to find two companies that would sell it in the quantity that I needed. I used Isolena wool, produced by a nice family run business in Austria called Lehner. https://www.lehner-wool.com/
Here is a link to their brochure that has tons of helpful information. https://www.lehner-wool.com/materialien/