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Trying a bivy bag for the first time

Since I am the third wheel on this next trip to Mt Baker I'm going to leave my tent at home, break my own rule (never use a bivy bag) and I'll be using a bivy bag there for the first time in my life. 

The North Face Assault Bivy Bag is on its way to my doorstep as I type and I'm not sure what to expect.  Worst case, I get no sleep at 9,000 feet and shiver a lot for six hours. 

EXPERIENCED BIVY BAG USERS:  What should I expect?  Tips, pointers?  Not overly interested in hearing from people who haven't used one. 

The weather report isn't quite stabilized yet but it will probably be around 30F and I'll be in a 20 degree bag on a fantastic pad.  Rain/snow?  No idea yet?

Well, I’ve spent a LOT of nights (like a couple hundred) in a military MSS Gore-Tex bivy sack, in every type of weather & temperature, and they do work. I have never gotten wet while sleeping in it, but getting in or out is another story. Looking up the TNF Assault Bivy I see they‘ve taken care of the 2 biggest problems with the MSS bivy - the top resting right on your face and no ventilation while still keeping bugs out. 

Given the packed size and weight of the MSS bivy I’m better off bringing my Fly Creek HV UL1 and having a lot more room. Even my 2P Marmot Hammer is a better choice, even though it’s heavier & bigger (not by much.) The Assault Bivy is pretty light, though. How many nights will you be out? For one or 2 nights I could do a Bivy, especially if I’m completely exhausted. Otherwise I’m bringing the tent and missing out on 15 minutes of sleep by pitching and striking it. 

I still use a goretex bivvy I bought about 35 years ago.  it works fine - no condensation or other issues although I sometimes lose some sleep because of the fabulous view o the night sky. 

The bivvy adds about 5-10 degrees to the temp rating of my bag.

Back in the day I tried a couple of bivies - found them to be claustrophobic.  The "roof" is too close for my comfort.  If you side sleep without also rolling the bivy, you end up breathing stale air.  I find trying to roll my sleeping bag troublesome enough, without also wrestling with the bivy and sleeping pad.  Dry entry/exit from a bivy is also a significant issue, particularly in the Cascades and coastal PNW.  Given the fact there are good UL tents with far more room for nearly the same weight, the only reasons I can count for going with a bivy are anticipating camp sites that lack terrain suitable for pitching a tent, and perhaps cost.

Jeff, I find myself more often the odd man on my camping trips, now that me and my companions  have aged.  Therefore I am inclined to believe this will not be the last time you will confront this scenario, that in fact it is likely to occur with regularity.  Considering you get out a fair amount, this may the time to invest in a decent tent that is light enough to carry solo.  The Big Agnes Fly Creek Phil mentioned is a roomy 3 season option.  It is marketed as a 2P, but you need to spoon your tent mate for that to work.  Otherwise it is a nice, wide 1P shelter.  The MSR Hubba is almost as narrow as a bivy, but has has a dry entry, unlike the Fly Creek, and had more headroom and sheds the wind better.  If you sleep in a shelter by practice, versus sleeping cowboy style under the stars, the Fly Creek will feel more accommodating.  But if you only use a tent to keep dry, the Hubba's protection will make up for its shortcomings.


I have also used a military bivy sack.  camo, gore-tex, zips and snaps to about halfway.  It's heavy, over 2 pounds, because the nylon is pretty thick, an entirely different level of weight and durability from what you ordered.  It's not very compact, i roll it up and attach it to the outside of a backpack. it does keep the rain off, has good seam tape, and has plenty of space for a sleeping bag, including a winter bag. it doesn't collect an inordinate amount of condensation. the interior usually feels a little damp in the morning. more durable than any tent short of a 4 season bomb shelter.  

I primarily carry it for extenuating circumstances - eg winds strong enough to flatten my tent.  find a low-lying or shielded spot and use the bag.  i used it in the winter a few times to test it out, but i always had the 'out' of retreating to a tent or partially-contained structure, namely the 3 sided lean-tos in some parts of New Hampshire's Presidentials.  doesn't have some of the bells and whistles, like no mesh to keep mosquitoes and no see ums off your face, and it's only so-so at cinching the face opening.  

at the temperature you anticipate and the gear you're bringing, good bag and pad, i can't imagine you'll be shivering unless you get some unexpectedly cold weather or high wind, and even the wind won't make much of a dent, except on your face.  

Digging the responses, thanks all.

I have used a canvas bedroll a lot with good success on pack and boat trips.  I have used a sil nylon draped over my sl bag and it works good on backpacking trips.  Sleeping under a tree canopy keeps the dew off without a bivvy or tarp.  Bivvies are too claustraphobic and clammy in wet climates. 

August 11, 2020
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