Originally Posted by
MassiveD
The only downside is a that they can make you sweat too much if you are doing something with spikes of effort. So sleep is ideal for them, high altitude climbing with a consistent slog rate is another possibility. Gear with lots of ventilation potential, like under arm zips is good.
Then I probably wouldn't take specific VBL clothing on a bike trip because it sounds like a terrible thing to wear while riding. But if you want something with some
VB qualities just put on your rain shell, not perfect, but I imagine it would reduce the water vapor getting to the bag, even if it is made from one of the "breathable" fabrics, although it doesn't sound as if it's really a problem. So maybe don't bother with a VBL sleep sack, just put on your rain jacket and pants.