I was recently reading about vapour barriers (Andrew Skurka’s site and Section hiker). It sounded impressive. The gear is not very expensive from Stevenson’s Warmlite (possibly the only R-rated outdoor gear catalogue in the world), so I ordered a shirt, gloves and socks. I’m nominally an XL, but L would probably fit better.
It wasn’t that cold over the weekend with temperatures into the low thirties, but I gave it a try. What seems to work is a wicking shirt like a polypro top, followed by a vapour barrier layer and then insulation. It was surprisingly warm with even a thin outer layer. Stevenson’s says it adds 15 degrees F when sealed up, and this seems realistic.
This got me thinking about cheaper ways to test out vapour barriers – I could have just worn my frogg toggs underneath and seen how that worked. But then what would I have done for rain (if it rained?). I’m tempted to try using a bivy sack inside of a sleeping bag (well sleeping quilt) to see if that works before finding a real vapor barrier liner.