Looking at buying a WM Hot Sac

http://www.moosejaw.com/moosejaw/shop/product_Western-Mountaineering-Hot-Sac-VBL_10016934_10208_10000001_-1_?cm_mmc=Affiliate-_-AvantLink-_-na-_-3816_0_ale_0&ad_id=Avant&avad=3816_0_ale_0

Then I was remembering a friend of mine who would take two Hefty Lawn bags, cut the bottom off one, duct tape them together and use it as his bivy. It occurred to me this could be a vbl in my bag if I could gather it up around my neck.

Having limited experience with a vbl, does anyone know why this Hefty bag contraption would not work as a vbl in my sleeping bag (ie. serve as a poor man's WM Hot Sac)?

Thanks in advance for any thoughts....

The hefty bag option would function as a vapor barrier. This is the equiv is using latex gloves as VB gloves or sandwich bags as VB socks. With all three options the primary issue is durability and maybe getting a comfortable fit.

--mark

First, what Mark said. Will definitely work, but durability and comfort (particularly w/Hefty sleeping bag liner). If you haven't used VBL before, it'd be a cheap way to try it out. I own a Hotsac and love it. One additional benefit of the Hotsac is the aluminized material preventing reflective heat loss. The material also feels nice, "layers" easily, and is generally quite easy to work with. I even carry the Hotsac as an emergency bivy on some day trips, and it's a great way to take my 30*F bag down to 15 or 20*F. Go for it!

I think this subject has been discussed before, but I'd like to hear some new advice/experiences. I'm expanding my BP season to include colder temps. Are VBs as effective/necessary as some suggest for below dew point temps?

Brad:

Thanks for your reply. A couple of questions/comments:

1) I've used a buddy's VBL - he thought it was an Integral Designs but it looked like a military issue item. I about burned alive in it with my 0 degree bag in 20 degree weather. I slept with my clothes on. I really wonder if it was just a simple military bivy - what I do know is that it didnt' breath

2) Your last statement helped me a great deal - I have been trying to ascertain how much it would boost my WM Highlite. Thanks.

3) What do you wear when you're in your Hot Sac? When I used my buddy's he told me to strip down but I just didn't want to do that - I ended up sweating through my underclothes. Just curious what you wear.

4) Basically I'm down to a) should I buy a hot sac to boost my bag rating to a winter rating OR b) should I buy a MB Alpine Parka and wear it in my bag to boost the rating (and have it as a "around camp" insulating item).

Any thoughts on these appreciated. Thanks to all for the posts so far.....

Edited by VanGo on 12/05/2008 11:35:15 MST.

I always use VBL gear in the winter when it's well below 32F/0C. However, I have a slightly different approach - I use VBL clothing rather than a VBL sleeping bag liner. Since I may have to sleep in my insulated clothing to extend the range of my bag (and for general comfort reasons getting up in the middle of the night) I use VBL pants and jacket over my long underwear and under everything else. This way, anything I'm wearing stays dry, as well as my bag. Plus, I put it on as soon as I hit camp, so I'm using it for much longer than when I'm sleeping.

Take a look at this company for VBL clothing:

http://www.rbhdesigns.com/

Don, have you or anyone else here used Gore N2S as your VBL layers? I saw them in MEC recently and was thinking of them vs. a silinylon suit.

I would *assume* that a Gore product is breathable, which would mean it *wouldn't* be a good VBL. Stephenson's WarmLight still makes VBL clothing, as does RBH, but not many others do.

Hey-
I wear a thin layer of merino wool--prefer Patagonia wool 2, but the 150-190 weight Icebreaker is good, too. I've noticed no difference in speed of drying between thin wool vs. synthetic layers when I keep either of them on.

As far as Hotsac vs MB parka, not quite a "fair" comparison. Remember, one significant advantage of the VBL is preventing evaporative heat loss--and in so doing, keeping your bag dry. The number one way of getting a bag wet is sweating in it... So for boosting your temp rating and overall "bag maintenance," I'd go with the VBL. Now, you'd still want a poofy down parka for around camp, and you could layer that blanket-style between the Hotsac and sleeping bag if needed. VBL clothing does have the mentioned advantage of being able to layer over w/worn clothing...

Oh, and to second the "when to use" comment, I bring the VBL on any trip expected to be freezing or lower, FWIW.

Brad:

Thanks for your comments. Looks like buying both is best. I have a parka but it's getting some years on it and weighs a whopping 2lbs - warm though.

Thanks.

I have found that a vapor barrier adds significant warmth when used in the west, but adds little or no warmth when used in the east. I guess you don't lose much heat to evaporation in the damp east.
It is valuable in preventing the moisture that your body naturally gives off during the night from being absorbed by your bag. It also results in less moisture within your tent.

The reflective coating on the Western Mountaineering vapor barrier doesn't add any warmth when it is used inside a sleeping bag, but does add warmth when the vapor barrier is used alone as an emergency shelter (which still leaves you cold).
I find a vapor barrier comfortable even above freezing. Even if I wear warm clothes under the vapor barrier the only moisture I find is a thin layer on my skin.

Putting on vapor barrier clothes under all but your bottom layer when you reach camp is a great idea, long ago suggested by the founder of warmlite, which I will try, probably in barrier clothes from rbhdesigns.

Sleeping in something thick and warm like a down parka only adds warmth if it has room to remain think within your sleeping bag. It only really works well under a quilt.

Hadn't thought much of the vbl and the humid east coast. I figured I got drenched during my last use b/c of too high a bag, too many clothes, and too warm a climate. Humidity in the east is a secondary presumption. It's always there but I haven't given it much thought.

Thanks for your input.

I'm looking at using VB as clothing as well rather than the WM hotsac so I can wear my insulation over it. Since I'm carrying the insulation belay & pants anway, seems a shame not to be able to wear it.

However, I find the warmlite & RBH stuff too expensive and too heavy for something I will only use occassionally in deep winter & end up carrying in my pack during the day when brought.

So I'm looking at silnylon stuff for the weight & cost savings. The Brawny raingear sold here at BPL looks like it has drawstrings to tighten around, so one could ostensibly get a smaller size & use is solely as VBL clothing. At 6oz and lower price feels like a better solution.

Anyone tried this or have any similar suggestions along these lines?

Tx...

Praveen - good question... I've been wonder the same thing. Hopefully someone here has experience with these as a VB.

Stephenson's 'fuzzy stuff' is wonderful VBL and rainproof fabric. At 2.2oz per yard it is twice as heavy as silnylon, but WAY more comfortable...

Would a GoLite Windshirt as as a semi-vbl? I dunno - new to this stuff for the most part.....

The Warmlite (Stephenson) VB shirt is $25, the pants are $39; shipping to MN cost me about $4.. If I had to do it again, I would have bought only the shirt and would have sewn the pants out of sil-nylon. Their pants designs is very simple and not as nicely cut as the shirt is.

Pricing: http://warmlite.com/prices.htm

Btw, my VBL shirt weighs 8.47oz, my pants are 4.69oz.

I found the previous thread from 2006 & 7. There is some info there and on this new thread too. I'd really like to hear more from BPers with experience that can give us more nuts 'n bolts of using VBs. Are Misters Caffin and Nisely out there with some wisdom and data?

>Would a GoLite Windshirt as as a semi-vbl?

Probably not. Depends on what you mean by 'semi'.

>BPers with experience that can give us more nuts 'n bolts of using VBs

I don't have any hard data on how much 'warmth' a VB will add, though the type of VB will make a difference. For instance, Fuzzy Stuff is clearly warmer than plain silnylon or hefty bags.

Aside from that, a VBL combined with a good bivy bag is your best protection against losing loft due to damp insulation. So it not only directly adds warmth but indirectly via loft protection. Of course, if you are only planning an overnight trip this may not be so important.