Originally Posted by fallkniven
When they said it acts as a vapor barrier, she meant that it won't breathe. Meaning and moisture/vapor that comes off you through the night, will pass through the quilts. Now if they're is a waterproof layer beneath the quilt, the moisture will get trapped in the down, instead of evaporating away,slowly loosing it's warmth. More of a concern the colder it gets.
I might have to test this when I get set up, of course no downy goodness for me as I'm allergic to feathers, but a simple weight test should tell me the effects. I have an odd feeling that if done right this could work well.