VBL allow you to lower bag rating so to speak

I tried that with temps around 0 F. Had insulated pants and a huge down baffled parka.
Couldn't zip up the bag around the parka and shivered all night. Too much wind getting in around the edges. Survived tho,and had fun during the days. Good skiing. If you don't
mind suffering or can build a snow shelter you can do it.

I would borrow an extra bag from someone to use over yours.Take a two pads too. A VBL
helps on multi day trips to prevent down from getting wet over time.

mark

the danger there is that youre pushing the insulation to its limits …

– a drop in temps beyond the expected
– poor nutrition or hydration
– reduction of insulation from moisture
– a long exhausting day

etc … can all possibly cause issues

in winter its usually to have a bit of a safety margin, especially if youve never done it before

the flash only has 3 oz of down i believe … most winter puffies have 6+ oz

Mark, if it is a winter camping class in snow country, then I assume that there will be plenty of snow. If so, then dig yourself a snow cave. A proper snow cave with one or two warm bodies in it will stay right around freezing point, plus or minus a couple of degrees F. That ought to be survivable in a 20 F bag without any VB.

–B.G.–

Mark,

Try out your bag/clothes combo at home in the backyard and see if:

1. the extra clothes do not compress the bag's insulation too much
2. a VBL actually works for you. (I recommend a SUIT of VBL clothes, like a very light rainsuit, v.s. a VBL bag)
3. a good sleeping balaclava that can cover your nose works for you. A cold nose is not comfortable at night – at least for me.

Also before the class be sure to buy "Allen & Mike's Really Cool Backcountry Ski Book" It's THE best little book on winter camping I've ever seen. The carton-like drawings have 1/2 the info.

I was afraid you guys were going to say that.

The snow cave is scheduled for day two I think, so will have to spend the first night caveless.

Not sure what I am going to do now, all my gear is so much heavier in winter not to mention wearing the heavier boots and then adding the snow shoes on top of that….I may die of exhaustion after 10 miles (only halfway kidding)

Probably making more of it than it is, but it has my head spinning with thoughts about moisture management and all.

I mean skiing all day is one thing, but I come home to a warm house, and change clothes, never had to stay out in whatever I was wearing in whatever condition it was in.

Thought about just taking another bag and using it as a quilt over my bag, but jeezus that gets heavy when you include the heavier tent, the shovel, the ice axe, the extra bag, and all the extra clothes (heavier stove etc).

I am taking Ned's class from mountain education up at echo summit.

I think the first night we hike from the snow parking lot to tammarac lake, then set up came, next day go to aloha lake and back, then 3rd day hike out. Not a ton of miles by any means and only about 1500-1700 feet of climb if I remember correctly (I did this hike one day this summer).

Should be interesting mid february.

Winter Camping:
Rule #1 Do your best to stay 100% dry. That means dry from snow, from rain, from sweat, or anything else.

Rule #2-99 Don't matter.

–B.G.–

Rule #2
No matter what you do when winter backpacking you will get wet from snow and persperation so know how deal with it and staying warm and keeping your lofted insulation dry.

Mark, I'm in almost the same situation as you. To this point, all my winter overnights have been to nice, warm, backcountry huts. This year I was planning to take a winter camping class but have decided to schedule my neck surgery in early February so I'll be good to go in time for backpacking this year. I also have a WM Alpinlite and am reluctant to spend a lot of money on a dedicated winter bag until I know I like winter camping. I do have a few weekends free before the surgery to try it out.

I'm going on a short, test overnight this weekend. The current forecast is for a low of 8F. I'm not too worried about weight since I won't be going far and will be pulling my pulk. Since the Alpinlite is a wide bag, I'm planning on taking an REI 20 degree synthetic bag that I have and putting that inside the Alpinlite. I've been plenty warm enough in the Alpenlite at 20F so I'm hoping that will be more than warm enough. The 2 bags combined are just under 4 lbs. That's about 19 oz more than the WM Kodiak I've been eyeing so that's not too bad for now. I had thought that insulated ski pants and a down jacket would do the job as well but I'll test that another time. I'll post back how this works out.

they show up periodically for sale used. and while they aren't listed on their web site any more, they will make you one if you ask nice. the auk makes a great, light 40* bag on its own. or for less money there are several big agnes bags that will work as over-bags for less than $100.

http://www.bigagnes.com/Products/Overbags

also, with this being a guided instructional situation the leaders may object to you using a bag that's not warm enough and making up the difference by wearing the equivalent of a belay jacket. that's more of an advanced fast and light technique and has a bit of a learning curve. have you contacted the instructor to see if they had a suggestion. you may also be able to rent a bag.

I'm surprised noone has mentioned the standard UL solution: wear down pants and top to bed. For the OP this ought work, as the Alpinlite is roomy bag. That's in fact why I bought one: when it's not too cold, the slight roominess probably costs warmth, but it adds comfort. If it gets super cold, it provides the space to wear some down extras that can loft properly to get the bag down to expedition levels. I have been toasty warm in the alpinlite plus montbell pants and top (and socks and merino balaclava) down to -22C

David people have mentioned adding insulated clothing to the OP's sleep system. Heck even the OP stated that he uses puffy insulation in his current system. Regardless the OP was asking about how much warmth he gain by adding vapor barrier clothing to his sleep system.

I use a vapor barrier when it's below freezing. I don't think it really makes me any warmer. On the bivy condensation thread here, there are more details on this. However, the VBL does keep the moisture from my body from condensing and freezing inside the outer shell of my sleeping bag. In other words, the VBL keeps my sleeping bag insulation more effective by keeping my body moisture out of it.

Really important, though–please don't wear any of your insulating clothing inside the vapor barrier, or your insulation will be very wet in the morning! From skin out: (1) light base layer (2) vapor barrier (3) insulation. If you're wearing an insulating jacket and pants to bed, the vapor barrier (maybe a cheap plastic rain jacket and pants?) must be worn under the insulating jacket and pants. Please keep that insulation dry!

I'd also suggest a really warm sleeping pad or combination of pads, maybe a total R value of at least 6.

My bad, I was skimming too quickly…

But in part I was responding to the worry some posters have of there not being enough room in the bag, and assuring people that this particular bag has enough room to let the extra puffy stuff loft.

I use the Adventure medical kits bivy sacks as a vapor barrier. The heat reflective material adds more warmth for me than a traditional vapor barrier; you get the benefit of both a vapor barrier and the heat reflection.

The tough part is that you can't take your insulation inside the bivy sack with you. My system typically looks like this: base layers, the AMK bivy sack, then all my puffy layers draped ON TOP of the bivy sack. Finally, I pull my sleeping bag or quilt over all of this.

This takes some fidgeting to get everything dialed in, but the puffy layers stay in place better than you would guess. You'll wake up a bit damp from the VBL but also sleep super warm! Getting out of the bag in the morning is chilly but you'll warm up soon enough with all your nice dry puffy layers.

The AMK thermolite 2 bivy weighs in at 6.8 ounces and costs $29. The "emergency" bivy is 3.7 ounces and costs $16. The thermolite 2 is clearly the more durable material and has better venting options with a foot vent and side opening. I'm yet to tear my emergency bivy though and usually take that along instead for the weight savings.

I have used my emergency bivy with a 20 degree down quilt, base layers, r1 hoody clone, with a WM flash jacket and generic puffy pants laid out on top down to near zero degree temps in snowy weather. This was probably the bottom margin for that setup but I still slept very warm. Those heat reflective bivys add a lot of heat!

This system definitely takes more technique than a traditional setup, but is also much lighter. Good luck!

i do the exact same as stephan with the 4oz emergency bivy …. not to the degree he does … i find it adds about 5-10F