I made a quilt with 2 layers of 2.5 Climashield XP, and got down to around 28 - 30F I think (if I remember correctly). You'd have to be wearing some very warm clothing to get down to 20F, imho.
"Civilization is the limitless multiplication of unnecessary necessities." - Mark Twain
“I go to nature to be soothed and healed, and to have my senses put in order.” - John Burroughs