I may very well be misinterpreting your hypothesis. From your math I am inferring that clo multiplied by weight per S.Y. gives a number equivalent to thickness of down. I call this your hypothesis because you included ??? after your calculation.
As I am about to embark on a synthetic quilt project, I have been contemplating all this clo business and following these forums, especially between you Bill and Richard Nisley. This has certainly been a mysterious subject, loaded with smoke and mirrors.
I took your math one step further to test the “reasonableness” of this clo times weight approach. Taking your measured 2.41 oz/SY times the .77 clo does give the answer of 1.848. Now, if this is an equivalent thickness of down, we can calculate how much the down would weigh to provide that same degree of insulation.
Let’s take a square yard of down that is 1.848 inches thick. That volume is 36”x36”x1.848”=2395 cubic inches. Now, let’s figure out how much down it will take to fill this volume; and we will use the “good stuff,” 800 fill power! (1 oz. of down will fill 800 cubic inches of space). Divide 2395 cubic inches by 800 cubic inches/oz. We get 2.994 oz.!
I believe that would mean that 2.994 oz/SY of 800 down, would be equivalent to 2.41 oz/SY of Climashield XP. In other words, Climashield is lighter than down providing the same degree of insulation! If we do the same calculation with Polarguard Delta, although the numbers are different, we get the same result the Polarguard Delta is more effective than down.
After studying the above figures, my gut feeling is that clo times weight isn’t directly comparable to an equivalent thickness of down. Of course I haven’t tested this out on that Brass Monkey … or is it a Copper Mannequin, they have over there in Europe to test such things.
Caution: this is nowhere near an expert opinion, just musings by someone who has been staying up too late at night, trying to figure out what to make my quilt out of.