Originally Posted by breyman
+1 on Andrew's article. It's a great summary:
Based on your brief description, it sounds like the vapor barrier did exactly what it was supposed to do. Keep the moisture in and not let it out to the insulative layers that can then have issues if they collect too much moisture without the opportunity to dry out.
It's tough to give a lot of advice without knowing more about your circumstance (what you were wearing, etc.). Many folks will wear a very light layer between their skin and vapor barrier to keep some of that claminess away. If you were getting cold because of the extra moisture inside, you might need to either get a warmer UQ, place one or two wool layers over you or consider hot water bottle, etc. to help keep you warmer even with the dampness. Oftentimes, folks will wear vapor barrier clothing to help keep that moisture a little closer to the skin, which when layered over can cause fewer warmth issues.
Excellent article, thank you for linking.
I can't argue with your assessment; my UQ was certainly unaffected by the moisture trapped by the space blanket, but I remember the following night I removed it completely and slept much more soundly. There was a small build-up of moisture on the inside (top) of the UQ in the morning, though. For short overnighters I'm sure this will be ok, but gradual degradation of the UQ's insulative properties would be a major problem for longer trips.
Appreciate the heads up, thank you.