freestone wrote:It is not necessary to use a bag liner to protect normal body moisture from the down.
There are two kinds of bag liner - breathable and VBL. Using a VBL above freezing is uncomfortable. Using the other kind of liner (silk, synthetic, etc.) is uncomfortable for me for other reasons.
And yes, sometimes, a VBL is a lifesaver, as it becomes absolutely necessary to protect the down from ALL moisture - if the warmth of your body is no longer sufficient to drive the moisture all the way through and out the breathable outer shell due to subzero temps, you are going to have your down turn into useless frozen chunks. Think Arctic Circle.
I do not qualify as an expert on this. I meant under normal three season use a down bag works well transferring body moisture out of the bag. I have a Versalite and go to the Sierra in October but never experienced ice in the down, it has always been on top of the bag and could be brushed off. I have no experience on long treks in extreme winter cold. The message I tried to convey is that liners add weight and have no multiple uses, its the UL in me. I guess I am unclear on the vapor barrier concept. Body moisture has to dissipate somewhere.
