Floatius, if you could update your profile to include your location it would make recommendations easier, since there is such a difference in availability of materials throuhgout the world -
For in-wall use, any open celled insulation with a density somewhere between 2 and 3 PCF will work fine, so cost/availability would help decide. The R-rated stuff, if it's the fluffy fiberglass, isn't heavy enough to work as well although it is better than nothing... Steve