Maybe this is a bad idea since nobody else has said it, but here is what I do and I have never had a problem with being cold. I usually have a 15-20 degree bag. Based upon a recommendation from a friend I started throwing a hand warmer pack into the bottom of by bag. I don't wear any extra layers and don't wear socks so that I don't sweat in them. Does a great job. I did just upgrade to a zer degree kelty but i imagine I will keep doing it. It does make it really hard to get out of the bag in the morning because it is so warm but I like it.