I would say less than a thimble full of condensation - see MedicineMan's video on our Big South Fork hang of NOV 2011. I was wearing 100wt fleece at the time. This weekend I was dialing in the radiant double bubble pad in a Deep Jungle. I felt slightly chilled/clammy in a cotton t-shirt at 52 degrees, yet toasty in 100wt fleece at 44 degrees - YMMV. As with any system with weather variables (condensation, temps, wind, etc...) one needs to experiment to find out what works.