Ive given up on tradition bivies because of the condensation issues and comfort level - and i dont live in a humid climate.I use a bivy tent hybrid, NF Asylum Bivy, which is heavy for BPL standards but much more comfortable and more room to move around in. When it comes to traditional bivies,, i have always wanted it to work, but using a down bag is just worrisome in them in random situations. I spent three nights in one in basically the same conditions and on the third night, had major condensation and minor down bag failure. It was only around 37 or so, but i was extrememly cold.
Im not a scientist, but it seems to me that condensation is a vicious circle... Once you get some, it creates more. I am actually quite surprised that my NF bivy is quite usuable in the shade in the evening in low 90 degree temps, as long as i cool down and stop sweating before i get in.
Dont know how hot or humid your area gets, but ive LIVED in a traditional bivy for a while in summer.... Its no fun.
Ive always liked bivies because i do stealth camping at times, and so i like the low profile. I think basically people have to use them in their environments to see if it works for them or not, everyones experiences seem to be different.
Ive never done the AT, but grew up in the Appalachian mountains. I cant imagaine using one during late spring and summer there, ev
With a large head bugnet.
The issue with getting a larger tarp is now you are slightly defeating the purpose of the bivy (perhaps except wind blocking) and could get a 6 oz bug tent instead and be able to move around and throw off your sleeping bag when its too warm. One of the advantages of the bivy is you pick a spot, throw it out, and get in. Now when uou add in the tarp, you need to set it up which defeats the convenience of a bivy, not to mention having to get it in if you have to pit the tarp low.. Adding in putting your pad and DOWN sleeping bag into the bivy which in itself is aggrevating at times.
Not saying it cant be done. Just things to think about.
As a side sleeper and using a down bag, if you ever need to shift the down back up tomthe top,in the middle of the night because of continous baffles that are considered a feature, its not impossible, but just not as easy unless you have a lot of room in there.
If you roll around a lot, you mit need to stake the bivy down and or not be close to anything that can puncture it. Prob not an issue to most, but in stealth camping, sometimes flat hiddeni spots are a premeium and you take what you can get.
Also you must provide full rain protection for your backpack, even with a large tarp IMO. got mice? They love to nibble on those bags in the middle of the night for entertainment sometimes. You can hang it on a tree prob in your area though.
If its very very cold, breathability becomes reduced because of frozen moisture on the inside. If you use an synth overnag for moisture management in extreme cold, good luck with fitting that in with a lot of bivies.
Got bears or mountain lions? Im here to tell you, a tent provides far more psychological safery then a bivy, and although both wouldnt stop either from attack, which i hear is rare for mountain lions, what if you did have to scramble fast? Ive had a mountain lion walk right next to my tent.... I cant imagine the dread being stuck in a coffin , i mean bivy, in that circumstance.
Also, this is totally my opinion... But i just dont think traditional bivies add much warmth. I just dont. My hybrid bivy, which has poles at the head and feet, provides an area for air to be warmed and i think provides far more warmth then a traditional bivy. Not a scientific evaluation but i am quite confident in the assertion.
Im not against traditional bivies. But these are my experiences with them, and for me, after long term use with them, i just got tired of it and basically switched back to a tent style one. Its not perfect either, but i am much more comfortable, breathes well, room for my synth overbag, no condensation issues so far (using in rain with tarp not tested yet), easy entrence in and out, headroom to lay on my pack and watch a movie on ipad mini, eat, drink, etc..., foot vent, so far in the shade is decently comfortable in low 90 degree, low humidity, weather....
I say test it out for yourself. It just seems people have different experiences and comfort levels when it comes down to it.
P.S. yes eric chan.... I use a 2lb bivy. im one of "those" people! Lol... In my defence, its more like a stream lined tent.