Originally Posted by monkeykoder
Insulation is primarily there to stop conductive and convective heat transfer. The material will actually re-radiate the heat out and you still end up losing the heat. The reflectix actually reflects that radiation back towards the source which we all know is where we want it in the winter. If your UQ stays warmer you stay warmer.
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.