Winter VBL sleep system

[300winmag]

Instead of using a Vapor Barrier Liner (VBL) bag to keep my winter bag dry I'm using a very light urethane coated and seam sealed rain suit.

The reasoning is that this suit will allow me to wear insulating clothes like my light down jacket over it and keep the insulating clothes dry. Sleeping bags sometimes need the help from a layer of insulating clothes to sleep comfortably through the night if a cold front pushes in unexpectedly.

My (very) heavy -20 F. Mt'n hardwear polarguard bag has a nice feature I see on very few other winter bags, namely a full length side zipper that reveals a 6" wide insulated expansion panel just above the main zipper.
In trying out this combo the -20 bag will easily accomodate my WM Megalite 30 F. down bag if hell ever freezes over.

[leaftye]

Wasn't there just another thread like this?

Anyway, earlier this year I got a silnylon suit from Antigravitygear.

[1azarus]

I agree -- it makes sense to wear vapor barrier clothing so you can wear the balance of your clothing over it. not sure it has any use in keeping your bag dry, though, why would it get wet? -- is that because you're using some kind of bivy, too?

[bigcranky]

Dry from the inside, lazarus. Over long periods in very cold weather, a sleeping bag can get very wet from perspiration.

This will work, but only in weather well below freezing.

[Toolshed]

Ditto on Big & Cranky - In deep winter conditions - Below 10 Degrees F, I use a VBL for trips greater than 2 nights. It can be as simple as a 12 x 2foot section of polyurethane coated nylon folded in half along the long side and sewed down both sides. Then a roll sewn across the top to hold a draw string to cinch it down over your shoulders or chest (depending on comfort level). you now have a 6'x2' VBL envelope.
It creates a micro-environment for your body, that at a certain humidity level, your body will stop perspiring. Some don't like the clammy feeling when you crawl out and hit cold air - It takes some getting used to. Others wear polypro in the VBL as it feels better than sticking to PU coated nylon all night.
I have some silnylon - hadn't thought about using that - maybe I'll giver a twirl