vapor barrier for new sleeping bag

[hikerfast]

i got this new -40 ems bag. They never are as good as they say, so if its good to -20, its christmas. its made of down, so i have the concern of sweating into it at night. i figure maybe i should get a vapor barrier for inside the bag. anyone have any comments/recommendations? i know nothing about any brands i could buy, or how much they are. all comments welcome

 

[Pete_Hickey]

I use a VBL always when it's cold. Not only that, but I also use a non-breathable bivy sack. The combination lets me take my bag well below its ratings. I did find that I had to seam-seal my VBL. If you don't use a non-breathable cover on the outside, this is probably not necessary.

I love using this combination, and don't mind tha clammy warmth. There are those who cannot stand it.

I have no idea what kind of VBL I have. I got it at Campmor, years ago from their clearance rack. I can't imagine much difference between different brands. they're simply a non-breathable sack.

 

[Chip]

You shouldn't need a VBL unless it's going to REALLY be -40. I carry one as an emergency bivy bag, but I've never used it in the bag. As far as sweating goes, the bags breath so it won't ruin the down. I have an inexpensive nylon bivy shell that I put my pads and the bag in to keep the package together, I've been happy to own that over the years.

 

[Chip]

I use a VBL always when it's cold. Not only that, but I also use a non-breathable bivy sack. The combination lets me take my bag well below its ratings. I did find that I had to seam-seal my VBL. If you don't use a non-breathable cover on the outside, this is probably not necessary.

I love using this combination, and don't mind tha clammy warmth. There are those who cannot stand it.

I have no idea what kind of VBL I have. I got it at Campmor, years ago from their clearance rack. I can't imagine much difference between different brands. they're simply a non-breathable sack.

But you sleep in igloos, drink Coleman fuel and commute in Canada in the winter on a bike, we're mere mortals. I'd have to imagine your bag is rated to 20, or something, and you're taking that VBL combo out to -50, no ?

 

[Pete_Hickey]

But you sleep in igloos, drink Coleman fuel and commute in Canada in the winter on a bike. .... I'd have to imagine your bag is rated to 20, or something, and you're taking that VBL combo out to -50, no ?

Not quite, but not TOO far off. Add/subtrace about 10 at each end and you've got it.

When I sleep in the igloo, I use my +30 bag, with no VBL Igloos are warm. I use the other combination when sleeping outside without a tent. Just on the ground, or in a lean-to. The wind whipping into a lean-to can really cut down on the insulating properties of a bag.

A VBL is also good for multi-day trips, in that it prevents the buildup of moisture inteh bag. Someone else who knows the numbers, will tell of the arctic explorers, and how heavy their bags became after time.

 

[Chip]

This is the Campmor regular length vbl I carry, they have a long also.
I got vbl socks at the same time and carry those as emergency/back-up gear as well.

 

[DougPaul]

For a single night, one need not worry about moisture collecting in the down--it is primarily an issue for multiple nights. However, a VBL will keep you somewhat warmer--hopefully not an issue in the NE with at -40 bag.

Dave.m has a nice bit of info on VBLs: http://home.comcast.net/~pinnah/DirtbagPinner/vb.txt

Doug

 

[hikerfast]

thanks for the responses. my concern wasnt warmth, it was keeping the sweat out of the bag. i was thinking of getting another bag, maybe a -20 with my other coupon. perhaps a vb would keep that warm to -30 or so?

 

[DougPaul]

thanks for the responses. my concern wasnt warmth, it was keeping the sweat out of the bag. i was thinking of getting another bag, maybe a -20 with my other coupon. perhaps a vb would keep that warm to -30 or so?

The difference in published weight between EMS's -40F and -20F bags is 11oz. Similar to the weight of a VBL.

The VBL also adds complexity.

IMO, not worth it for a short trip.

Doug