Help with Bivy Analysis Paralysis

You should have less condensation with the eVent.

I am sure you have found my piece on bivy’s here

I’ll share my experience. I use a silponcho (approx 5×8) and a large borah bivy in m90. I use this setup when no or light rain is expected and it worked ok. No condensation and no problem with the rain. I’m not big, but the large bivy felt great with a wm badger and a  neoair xlite. I will now use it with a EE quilt.

I never had condensation problem with toddtex or goretex bivies, but never used them with the hood. I changed for the borah when I understood that I will never use a bivy under heavy rain, or without a tarp under any kind of rain.

for 3 season use in the coastal PNW … theres a decent chance with condensation with any bivy regardless of type, well maybe not the bug bivys

since its the perfect test season with the week or so of constant rain … do a simple test if you have some nylon fabric laying around

setup a tarp, yr neoair, etc outside … wrap your sleeping bag like it was a bivy … and sleep overnight in it … the bugs arent out in full force yet so you should be fine

you can even use yr windshirt on one part and yr rain jacket with the other part (use some light tape to hold them down) so simulate both fabrics

do this for at least 2-3 days to simulate a multiday shoulder season trip … make sure to leave the gear outside and sleep outside all those days (dont bring it in)

if your test was anything like the one i did years ago, youll find out that in high humidity situations youll get condensation inside the bivy, and because theres little air gap (unlike a tent) the condensation may soak back through where the fabric touches the bag

i own an event bivy sack and it wouldnt be my first choice with down in constant humidity … for fast 1-2 days hikes and climbs in good condition its fine … in snow its not too bad as the condensation turns to frost and you can whack it out … but above freezing in the rain, with down?

im working on a way to keep down dry even in multiday PNW no sun all day rain situations … the tent test was succesful, next up is to test it in a bivy in multiday rain the next week or two … but itll add weight

to be blunt … in PNW coastal rainy season use a larger tarp (perhaps with a bug bivy/net) or a double walled tent would be my recommendation

;)

Perhaps bivies are obsolete.

With large super light shelters (especially Cuben), you can get a large tarp (8′ X 10′) or a mid for what a bivy weighs. Years ago, on of the lightest setups was a Poncho/Tarp with a bivy to handle the coverage problem of a smallish shelter. I haven’t used a bivy since I bought my first Cuben shelter. The larger, although light, shelter solved all the bivy-induced problems.

nick …

bivies are still useful for snow caves, climbing (small ledges), emergencies, sleeping under the stars, etc …

but i think yr correct that it doesnt save too much weight on the fancy UL shelters … it does save quite a bit of MONEY however over a cuben tent, borah gear sells a bivy and tarp for ~120 yankee dollahz at ~16 oz

heres a good link for the OP … note its for dryer conditions … not the PNW shoulder seasons

https://40yearsofwalking.wordpress.com/2011/07/04/the-bivy-condensation-conundrum/

;)

For what it’s worth, I used a Borah Gear Cuben bottom/50 top side zip under a YMG Cirraform exclusively of r a couple of years.  I use a NeoAir and EE quilts either 30 or 0 depending on the weather expectations.  I have been fortunate enough to not have condensation challenges, but I spend my time in the Sierra and although cold, humidity is typically not a challenge I did spend a couple of really wet nights with high storms rolling over the top and I still was good under the Cirrraform/Borah combo.

bivies are still useful for snow caves, climbing (small ledges), emergencies, sleeping under the stars, etc …

True, but most of us here don’t sleep in snow caves and we don’t climb. I normally sleep under the stars sans bivy.

In crappy weather, using a small tarp and bivy, it is difficult to cook, sort gear, or do other end of the day chores, and with most setups you can’t sit upright.

Then there is the issue of condensation. Usually a bivy compounds it. About a year ago I was sleeping under the stars and woke up in the middle of the night needing to take a leak. The top of my bag was covered with condensation. When I woke up in the morning it was completely dry… wouldn’t have had the same results with a bivy.

Yes, there are some situations where a bivy would be helpful.

For the OP, there are many variables you need to take into consideration; there is the plus of a bivy under a minimal shelter in bug season. Bottom line: there is no perfect solution nor any right way. Weigh (literally and figuratively) your options and adopt the one that makes the most sense to you and the environment you will normally be operating in.

I use an M50 bivy in PNW.  Very little condensation but I don’t breath into it.  Down.

I use it by itself if it’s not raining.  Protection from dew, wind, blowing dirt or sand.

If it is raining, it protects from rain splash, wind, condensation knocked off of bottom side of tarp, blowing dirt or sand.

I don’t think eVent breaths as much and is heavier.  That would be good if you wanted to sleep in rain without tarp.

When I lived in the PNW, I found a larger cuben tarp worked better for me and weighed approximately the same, if not less, than a smaller tarp combined with a lightweight bivy. I tried a TiGoat Ptarmigan and MLD SL Bivy, both with full head nets, and found them both somewhat prone to condensation. Therefore when bugs were and issue, I used either a headnet or bugbivy underneath the larger tarp.

Thanks for the suggestions / thoughts.  My primary goal is to reduce weight when I’m not with my family.  It seems like a shaped tarp like the SMD Deschutes might be a better fit.  I was looking at it before bivys caught my eye…

it all depends how serious the rain yr expecting is …

if its multiday non-stop without any sun then what may happen is the inside of your shaped tarp may get condensation from yourself and the ground … and as the rain hits the tarp it knocks loose some drops resulting on some spray on the inside

heres some spray on the inner of my TN tent from that issue … i also use the outer fly as a “tarp” …

you can see how without some kind of protection things might get damp over time … at the very least the DWR on you bag/quilt should be kept refreashed

a bug bivy or net would reduce the issue

im also working on a way that may prevent the issue with common items i guarantee everyone here has in their house … it should also preserve the down loft in humid PNW rainy conditions …

ill post up about it when im finished testing

on a side note if i was to design a “better tarp bivy” i would have 2 or 3 points that could raise the bag high enough to have more ventilation and not touch the sleeping bag as much … then i would add a strip of mesh lower down towards the feet

but then i have no idea how to sew

;)

” if i was to design a “better tarp bivy” i would have 2 or 3 points that could raise the bag high enough to have more ventilation and not touch the sleeping bag as much”

On my TiGoat Bug Net Bivy I had them add an extra pull-loop around knee level in addition to the one up at the head/neck region which allows the net to be lifted off from you. I’ve found this setup works well with the MLD Grace Solo or Duo as it has hooks on the underside of the ridgeline to connect the line.