UPDATE FROM 3/11/2009. OK, I'm going to try and put this in a way that even I will understand. RBH Designs makes vapor barrier clothing. The VB theory is simple: put an impermeable membrane – some people just use plastic bread bags – between your skanky, poisonous skin and the insulation layer.
Two things happen: first, sweat doesn't get into your insulation layer, so it remains dry and keeps you warm. Second, once the skin covered by the VB gets humid enough it stops sweating, preventing evaporative heat loss. The most popular VB products appear to be socks and sleeping bag liners. People who have tried VB products either swear by them or swear at them.
I finally tried for myself with RBH's VaprThrm insulated sock (he hates vowels!). Much less fitted than a normal sock it has a soft inner lining, a VB membrane and a fleece outer. They seem too thin to work, but after wearing them inside a plastic ski boot in single digit temps they kept my feet plenty warm with no other sock on. The main complaint most people have is that their feet get too wet with all that sweat being held in. I'm a light sweater, and I didn't have that problem: my feet were barely damp, no standing water at all.
After my initial positive experience I gave them a shot on Denali, and that's where I ran into a major problem. They still proved warm and not too damp, but I got some nasty blister lines along the stitches on my shin. A little mole skin solved the problem, but I can't recommend these as a stand-alone sock for serious mountaineering use. RBH also has a bonded VB sock with no vertical seams that would require an outer sock. Those might do the trick, and I'll try to get those reviewed next season.
3 responses to “RBH Designs VaprThrm insulated sock”
Interested to hear how they work for you in mountaineering boots. I have a pair and tried them in Sportiva Trangos boots, and while they kept my feet warm relatively non-sloppy, the stitching across the top arch/bridge became very annoying after a few miles. I had two hot spot lines on each foot after removing them. Seems to me (sorry for pun) that the stitching should be further off to the sides of the foot bridge/top arch…
I used both the insulated and the non-insulated RBH VprTherm Socks on Denali and on some trips in the Swiss Alps. I had no problems with the stitching lines of the insulated socks and I was surprised how comfortable the insulated VprThrm socks were. Funny feeling to step into plastic ski boots with a loose fitting liner and no socks. But especially with the thinner RBH VprThrm Sock I found that after some time of wear and tear in the boots they gradually work less perfect and sweat is working its way through the liner and soaking the outer socks and the liner of the boots. By the way, his happened with any liner I tried so far. So, better go back to the bread bags?
your sweat cannot get through the sock to jeopardize your insulation or your feet. While the seams are not sealed, these advanced vapor barrier socks will keep most of the moisture next to your skin and out of your boots.