Hung in my backyard last night but had to bail just before sunrise due to a chill on my back that just wouldn't go away, no matter how hard I tried to ignore it.

I was laying in my BB with a regular blue foam pad with extra pieces for my shoulders and thighs. The low was 8.1F. My toes were cold for the first hour or so, but they warmed up. I was snuggly and warm for the next several hours until my back started feeling cool. Tried readjusting the thigh pads to under my back to no avail, and decided to go inside before I started shivering.

My initial suspicion was condensation or sweat, but upon closer review indoors, everything felt dry. I realize it's different for everyone, but what's the minimum temp rating for one layer of CCF?