I was brainstorming a colder weather sleeping system for ground camping in winter.

Generally it is cold and wet here (30s and rain) but we do get several weeks of weather that is dry and cold (teens to single digits). I want to do some hiking/camping during this time in our mountains. (I live in SE AK at sea level so I'd be at 2500ft or so max)


I have a synthetic 15 degree bag and several down quilts. It is my understanding that for weather conditions where condensation would be an issue you are supposed to put the down next to you and the synthetic on the outside. Since I have a bag, what would the ramifications be if I layered the down quilt over the bag? Would I want to use a bivy too or would that compress everything and be counter productive.

My winter camping to this point has been limited to hammock camping with an underquilt/pad/sleeping bag arrangement.

Thanks,

Chris

PS. If Santa deems that I have been good, he may bring me a synthetic quilt but I'm not holding my breath!

Edited by ChrisHanson on 12/14/2010 21:33:02 MST.

There was just a thread about this in Gear section. The issue was condensation in the down, if I remember correctly.

and I did - took me a while - but here is the thread.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=39299

Doesn't sound like it is something I would want to try.

Mike

Thanks, I didn't come up with that thread when I searched.

Did some testing with this a few years back when i lived in NE.

Best set up for what you described would be to layer down under synthetic bag in a bivy, providing there is enough room to not overly compress your insulation.

Spoke with Ryan Jordan and Alan Dixon on this one and they both agreed on this set up for sub zero conditions.

Stay warm
Jim

I am interested in this as well. I am planning on trying it out shortly in preperation for another trip. I have a 15* and a 20* bag, both down, and I hope to use one as a quilt over the bag for some -F temps.

I think the dewpoint will ALWAYS be inside a bag unless it is so thin that you are loosing a lot of heat through it???

What would the ramifications be if I layered the down quilt over the bag?

Back to Chris on this.
Heat tends to move upwards and pass through the inner layer just fine, by the time it passes though the second layer it tends to cool and turn into a vapor which starts to accumilate in the outter layer of the sleeping system. With down being the outter layer that would start to compromise/collapse the loft, synthetic insulation tends to handle this moisture build up lessening the chance of loft degradation.

Conditions when testing were camped on a 5' snow base, in a floorless mid with temps dipping to -15-20 below zero, mostly dry air. There was two of us testing different set ups. Down bag inside a synthetic quilt combined with a bivy and foam pads performed flawlessly. Down set up alone that was used had moisture issues on the outter surface by the am.

Jim

Jim, did the down bag have moisture in it, or just on the surface? Was it on the surface close to the sleeper or the outside surface exposed to the air?

Edit, it looks like you are saying on the top surface exposed to air, just making sure I am reading it right.

Edit Edit. Could the moisture have come from the fact that the upper side of the down bag was cold/not warm, so moisture would condense on the outside just like it would on the inside of the tent, rather than moisture coming through the inside?

Edited by Any-Cal on 12/13/2010 12:27:31 MST.

same applies to bags as to clothing ... itll end up in the outer layer

http://www.umanitoba.ca/faculties/physed/research/people/giesbrecht/Cold_Weather_Clothing.pdf

Hi John,
Outer bag's surface did have frost on the top of the bag and also enough moisture within the bag itself to notice a slight loss in loft, we were only out for an overnight trip on this one, any longer and would have needed to use VBL to help retain loft. Have noticed this on winter trips where moisture tends to be the result of warm air passing through insulation and turning into a water vapor as it tries to pass through the outter layer and freezes.

Seems that most breathable fabrics used tend to fail after awhile below certain temperatures with being over welmed by prolonged moisture vapor trying to move through outer surfaces and outside temperatures being cold enough to freeze almost on contact after a certain point.

Hope this helps

Jim

Edited by florigen on 12/13/2010 13:30:31 MST.

Thanks Jim for the additional info, and Eric for the diagrams. They show graphically what I suspected.

It really isn't what I was hoping for, but I guess it is hard to buck physics...:D

Thanks all. I ordered a MLD quilt to pair with my down quilt (early Christmas to myself) and hope to try it out when the weather and my work schedule permits. Thanks to all for the insight and input. This forum is such a wealth of knowledge!

I recently found my old High & Light (c. 1970s) down top which zipped to a nylon covered open cell foam mattress. I unstitched the zippers from the down top and plan to use it as a snap-on top over my WM Megalite 30 F. bag. Four to six sew-on snaps should do the trick. BTW, the mattress section has been discarded. It was an idea that never worked well. High & Light has been long out of business.

When I get condensation in the top I'll merely unsnap it and lay it in the sun to dry. Since I can shake some down from the top to the bottom of the Megalite I can shift it around as needed.

With this combo and an Eddie Bauer down "sweater" and Cabela's down pants I should be able to sleep in temps in the low teens at least if not down to 0 F. Below those temps I'll be forced to carry my monsterous Mt'n. Hardwear -20 Polarguard Delta bag.
Speaking of which, it has the neat extra of a full length zippered gore that is 6" wide. I can open it up, expanding the bag, and have enough room for my Megalite bag inside for truly uncivilized temperatures.

Also I have a very light nylon urethane coated, seam sealed rainsuit to use for a VBL suit if I plan to camp more than 3 days in frigid temps.

here's a possible solution to the problem

http://sectionhiker.com/vapor_barrier_clothing/