i’m not sure thickness of insulation by itself is a good measure of insulation power. not sure about anybody else, but somehow i feel warmer in half an inch of fleece than half of inch of down.
i think it’s because not all dead space* is created equal. it’d be neat to run those sleeping bag tests on a down bag, a fleece bag and a synthetic bag, all of the same design, all of the same thickness.
http://www.backpackinglight.com/cgi-bin/backpackinglight/sleeping_bag_rating_commentary.html
anyway, it’d be neat to have another metric besides thickness to judge warmth. that could then be considered with respect to weight. don’t get me wrong, i still think down would win, but i’ve a feeling not by as much.
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*a space small enough that a convection cell doesn’t develop.
