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I was thinking it yout took two contractor grade garbage bags and duct taped them together you might have a light and inprenatable bivy sack.... the concept of vapor seal could work for you are against you or not come into play at all.... the idea I have is that your breathing would be directly outside as not to build up condensation. I am going on a elk hunt in a few weeks and it will have a few overnighters light and spartan...any "tent" I have used in the past ended up being horribly drippy wet and cold on the inside later in the year...
a good bivy sack is water proof on the outside but let's moisture out from the inside. personally I like a one or two man ultralight tent far better than a bivy sack.
x2.....I could it as a "emergency bivy" in a survival kit but I would never choose it as the 1st option to sleep in.
Your bag will be soaked in the AM. Good luck
Your breathing isn’t your only source of moisture .... your body will breath a quart of water overnight . Where do you think that quart will be in the morning?
Stick w a bivy bag
That's what I was thinking just wanted to run it up the flagpole...
This idea would benefit from a backyard test run on a rainy night.
I watch the weather closely and pack accordingly...with all the moisture supposedly shed by out bodies how come our sleeping bags aren't soaked at the end of the night is the moisture really transfering that efficiently through my sleeping bag..??? Serious question....
Yes... moisture leaves the body and a good bag transfers it to the atmosphere. There is a minimal amount that remains and you should “air your bag out” occasionally.
On exceptionally cold mornings I’ve woken to “hairs” of frozen moisture extending from the seams of my bag. Proof the bag is “ breathing “
would Tyvek work? it is supposed to allow water vapor to pass through.
Every time I've used a bivy I wake up in the middle of the night freezing my ass off and soaked. I've used goretex, and some sort of breathable (my ass) treated silicone. You'll be surprised how much moisture just leaves your body when you sleep and in my case it's way more than "breathable" fabric can handle. I'd just use a tarp shelter and skip the bivy. Give it a try at home 1st so you can go inside when you're soaked.
Garage bag is a bad idea..
Used two garbage bags for those raining or heavy dew nights one summer riding my Super Glide around the country back in the 70’s. Stuck my legs in one and stripped the other over my head with a breathing hole . Worked like a charm even in a prairie deluge but getting that Hog out from behind that shelter belt along a muddy corn field was brutal.
Not good for sleeping but a big contractor bag makes a great emergency poncho, clean spot to stack meat, dry place to sit, backpack rain cover, water catcher if stranded, and of course..a good place to put trash. I have carried one in my pack a lot and it always ends up being used for something.
I’ve used contractor bags as ponchos, backpack covers, and meat that was already in a game bag to put in water or hang. They’re invaluable and I always have a couple along.
I’d only sleep in one in an emergency though.
I have a really big contractor bag I used to carry for emergency use. Its tall enough that one will do the trick and would keep you dry (er) in a pinch. I have since replaced it with a SOL escape bivy which is a better option but bulkier and heavier than the garbage bag.
I've used a plastic tube tent for weekend bivys before. Essentially what you are describing, heavy plastic with both ends open. Run a cord through the center tree to tree and some rocks on both ends on each side make a triangular shape tube. Worked well enough for a few nights.
Bad idea. I had a bivy tent that would get condensation on the inside. I thought "I'll slide my sleeping bag into a contractor bag and my feet/legs won't get damp from the condensation on the tent."
Within 15 min I felt damp and clammy. As stated, substantial condensation is coming from your skin/sweat, not only from your breath.
You're idea won't work. Except for perhaps in an emergency.
Look at it this way, if you need a water source in the AM, make sure you move real slow getting out of your contractor bag as to not spill the contents. No filter needed!
I agree with Grubby about the SOL Escape. I have spent some miserable nights wrapped up in those foil space blankets. They may provide some thermal insulation and definitely provide a wind break, but you will get clammy. They tear and are not really reusable either. The SOL Escape breathes, breaks the wind, provides more insulation, and is reusable. I can live with the slight weight increase and bulk. One is always in my pack. Even my daypack.
And it can be used as an expensive game bag in a pinch.