VBL question

[Edward Jursek]

Anyone have an educated opinion or source or thread that estimates how many degrees a Vapor Barrier Liner will boost the temperature rating of a down bag? In my case the vbl is a Zpacks .34 cuben one.

[Anonymous]

Haven't ever seen exact numbers/hard research for this. An uneducated guess would be somewhere in the 5 to 7 degree range, and potentially more for a heat sheet if you have some space between you and same.

[Hiking Malto]

The big disadvantage to a liner is the inability to wear insulting layers so your clothing in Essenes is not multiuse. With clothing such as a cuben fiber rain suit, you can wear clothing as needed over the suit. As to how many degrees, I can answer that exactly for clothes but I have yet to be cold in VBL and I have had it down to about zero when used with my Golite Ul20 quilt and bivy. I believe the biggest bang for the buck is booties. Those will be the first to be used even I don't completely suit up.

[Anonymous]

Agree with Hiking Malto, VBL clothes are more versatile and pragmatic. Just made myself some silnylon VBL booties and top funny enough.

Regular Cuben is great for tarps and tents, but i really don't see the point with smaller items when silnylon is so cheap, durable, and there isn't much weight difference between smaller items like booties, tops, etc

Cuben's abrasion resistance sucks big time, unless you go up to the 1 oz/yd2 stuff which weighs almost as much as silnylon, which will still be more durable long term. Thinner cuben develops pin holes, which while it may not leak water, will likely leak moisture vapor no problem and then your VBL is not really a VBL anymore.

[Jerry Adams]

I made VBL pants and shirt from "fuzzy stuff" from Stephenson Warmlite. Didn't really notice any temperature reduction compared to non VBL. Probably Justin's 5 to 7 degree F is right – that would be hard to notice.

I think the case where VBL is good, is if you're doing many nights at really cold, like an Arctic expedition. Stephenson Warmlite talks about this. Gradually your sleeping bag will absorb moisture, get incredibley heavy, and lose insulation effectiveness,

[John Almond]

I only use VBLs for my feet (repurposed veggie bags from the supermarket) and occasionally my head ($0.10 shower cap).

I've found that my feet get between 10 and 15 degrees of warmth, but my feet sweat BAD.

My head has only been on nights where I was right at the edge of my insulation's rating, but I'd buy 5 degrees of warmth. Somewhere in that range, anyway.

Hope it helps!

[BlackHatGuy]

Not sure it answers that specific question, but this is the best primer I've found on VBL use:

http://andrewskurka.com/2011/vapor-barrier-liners-theory-application/

[Jerry Adams]

I tried using plastic bags on my feet and the skin turned into prunes. The skin was much softer and liable to damage, I thought, so I took them off after one day.

Maybe I should have put the bags over thin liner socks.

[John Almond]

Yep. Used my hiking socks as liners (I use thin running socks), since they were damp anyway. And when I did my head, I used my thin polyester balaclava as a liner.

Hope it helps!

[Steve M]

Edward if you have a low perspiration rate (?) a sleeping bag VBL liner may work well for you. Last night I finally got to view the Geminid Meteor shower and used an older 40F down bag at about 29F. I used this as the VBL inside my bag:

http://www.amazon.com/Adventure-Medical-Kits-Emergency-Bivvy/dp/B000WXX0JS/ref=sr_1_1?ie=UTF8&qid=1418581523&sr=8-1&keywords=heat+sheet+bivy

I also added an extra fleece hat and the combination worked well.

[James holden]

You can easily use your down jacket as extra insulation with a VBL liner

Simply put it between the liner and the sleeping bag, use it like a blanket

;)

[michael levi]

A good happy medium is for example, a loosley draped half yard (18 inches x 52 inches) of .51 cuben fiber draped over your cold feet and torso. This will not trap every btu of body heat but it will hold some of that valuable heat in. It will most importantly allow moisture to escape reducing chance of wetness.

A half yard of .51 cuben only weighs .255 ounces! I would probably say that for the weight this is the warmest item you could have. a plain peice of cuben is also good for blocking rain when tarping.

[JP]

I was stupid and used a pair of Stephensons VBL socks the first time for a trip into the BWCA over new years last winter that was suppose to last 8 days. After one night I ended up calling it a trip due to the VBL socks blistering up my feet after only 4 miles skiing across a lake with a pulk. Not a place I wanted to be dealing with limited mobility and up against the 8 ball, and no easy way to get them dried out in sub zero temps.
My foot wear system for that trip was Cabelas Cool Max liner socks, Stephanson VBL socks, Smartwool or Darntough wool mid calf socks, and Steger Mukluks for boots.
These photos were taken the first night out, minutes after setting up camp, so the blisters weren't quit developed yet. When I got home they were silver dollar size on each foot.

I went back up to the BWCA 1.5 months later in February and had the trip of my lifetime without the use of VBL clothing. I had a few people question wether my Mukluks were tight enough in the foot, and all I can say is with the few hundred miles I have on them, the only time I received a blister was with the VBL's.

May work for some but I have read enough stories that have had the same outcome as mine did.

I did buy a VBL bag liner from RBH for the second trip, but I didn't like how narrow it was compared to my WM Puma and Kodiak sleeping bags and ended up returning it before the trip. I don't plan on using a VBL in the future. Our bodies are not made to be clammy. This only leads to problems, at least for my skin.

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