It appears you can nearly double the R-rating of hiking mats or other gear by filling them with eg CO2 which is cheap and readily available instead of eg air or nitrogen. I can see how this can easily be done eg with closed cell foams, but for an inflatable mat you would either need to carry a (heavy) canister or have some way of re-compressing the CO2 into an acceptably small enough space. Still, an interesting idea.
