When I day hike in winter I carry a light nylon (7.6 ounces) bivvy sack and a very light Mylar bivvy sack (2.5 ounces) for spending the night out in an emergency. My question is this: If I were to sleep out in cold weather should I put the Mylar in the inside like a vapor barrier, or on the outside? Both are waterproof so rain or no rain shouldn't make a difference.
Jim M