Oh I totally agree. I bought a cheap north face 40 degree bag, It's small and lined inside with nylon? I plan to get a better bag but when the temp dipped to 35 I froze all night and when I woke it was clammy as ever inside the bag. Why is that? I might as well have taken a swim and then climed in the bag. I've never experienced that before even when sleeping in the snow in a cheap coleman bag when I was a kid. Of course the bag then was lined with cotton fabric. Learning the hard way is not nesessaryly the best way. My next trip (soon) late summer. I will use a bag liner for now.