I know that goose down is warmer than cattail down. But what are the R-values of each? How much warmer is the same weight/volume of goose down compared to cattail down? Is cattail down better than low-quality goose down?
I had never heard of "cattail Down" but after a quick google, it sound like it is significantly heaver than duck or goose down.
The R-value dose not measure a substances insulation value, rather the finished product [Ie. pink fiberglass insulation may be R12/R20 or R40 depending on the thickness and how it is manufactured].
Vary generally, you can think of downs insulating property's as being proportional to the weight/volume ratio, 1 cubic foot of 700fill down will give the same amount of thermal protection than 1 cubic foot of 800fill, but the 800 will weigh less.
Therefor if cattail is denser [heaver proportional to volume] than goose, it will give a lower R-value if you filled two of same jackets.