bivy vs tent in high winds

I think it depends on what you expect. If you just want warmth for sleeping, a bivy will shed the wind effectively to give you that; and it’s pretty easy with a bivy to pick a spot that has just a bit of shelter from the wind, as in behind a low rock or bush, where a tent would not get that benefit  due to being taller. But if you want a refuge from the wind, where you are protected while doing something other than sleeping, then a bivy will not cut it.

tents can be knocked down by wind.  I don’t care what tent you have.  Tents that will stay up better are heavy.

a bivy is already “knocked down”.  My bivy has tent stake loops on 4 corners which helps.

One thing I don’t like is dirt and stuff will get blown into the bivy.  And my stuff can get blown away.  A tent offers better protection.

If I parsed your post correctely, you expect there will be times when you are carrying the 2 pound plus pyramid, but need to just bivvy overnight a (one pound?) bivy.

If you have not purchased this kit yet, there is a class of sub-3 pound, low-profile tents that you might want to look at, some of them marketed as four season: Black Diamond First Light, SlingFIn, Big Sky, and others.

I’ve used many a bivy over the years (you can search back to 2006 on these forums to see that) and no matter what I did and no matter what fabric used, I consistently had condensation.  To the point where it was dangerous (just below freezing – no way to dry out my sleeping bag).

If you want extremely good wind performance but in a shelter that you can move around a bit in and avoid condensation (as much as possible), something like the MLD Trailstar would work well unless you were expecting a ton of snow.  In that case, that Silvertip looks to be an amazing shelter.

I haven’t purchased the bivy yet, but was planning on carrying both at the same time. I really like the shaped tarp for its vestibule area, along with being able to dig snow out of the bottom floor for more space. I wanted to get a bivy for those lazy days where I don’t feel like staking stuff out and for unexpected weather conditions. Probably just going to get a XL Sol emergency bivy to use as a safety measure and call it a day. The condensation issue seems like more trouble than its worth.

don’t breath into your bivy and you won’t have condensation.  Leave the door open so you breath directly to the outside.

I would do a MLD Duo Mid and my Borah Gear snowy side Event bivy..

I have not had any condensation issue using that bivy or my bristlecone bivy in the past when I used to use them.. Before I started hanging.

Like David, I’ve had too many bad experiences with condensation in bivies.

When I bring up these terrible experiences, I am constantly reassured that with the right combination of site selection, meteorology, dew-point reference charts, barometric consultations, prayers, crystal balls, and a touch of sorcery, they work great.

But as they say…

Ain’t nobody got time for that.

I wanted to love the bivy, I really did…and I really tried.  But I now opt for wind-worthy shelters that don’t require a bivy to be warm or dry.  And I cowboy camp more often than I use shelters.  Wind or not, I rarely encounter conditions that an appropriately warm bag alone can’t handle.

“When I bring up these terrible experiences, I am constantly reassured that with the right combination of site selection, meteorology, dew-point reference charts, barometric consultations, prayers, crystal balls, and a touch of sorcery, they work great.”

That never seemed like a good explanation to me, good response : )

But like everything, different solutions work for different people.

I think the way bivies are intended is to have your head inside, in which case you breath inside the bivy and condensation will happen.  If you can open up the bivy and have your head outside, then you can avoid this.

finding some random image on the internets, this one would work:

I dunno if I could live in a bivy. In wet weather or snow it’s impossible.

I see my solo TT Moment DW as a “tent/ bivy”. It’s small, aerodynamically shaped but large enough to sit up inside, change clothes, store gear in the vestibules and cook in a vestibule if necessary. In other words  I ain’t living in anything smaller!

With the guy points on the newer Moment DW fly you can withstand very high winds. This includes the fly hem stake loops that are necessary to totally nail it down in high winds.

A fully enclosed tent will almost always be warmer than a bivy in high winds, because wind compresses dead air space in the bivy, and a bellows effect results in a bit of heat loss. In a tent you are surrounded by (generally) motionless air and it’s a lot more pleasant.

Condensation: with no wind all bets are off, and condensation is a risk with any shelter and especially with a bivy at temps less than 35 deg F.

With wind, you have low water vapor pressure at the outside surface of the bivy and so, a good VP gradient to drive moisture out.

It all depends on the terrain, and on the usual weather where hiking.  That affects cooking, eating, peeing, excretion, condensation, and whether you can survive the night in a bivy under microbursts, sleet, flooding and other things you could trek for years without imagining possible, but then get demo’d by.

So one year my hiking companion and I decided to try bivying with tarps.  We camped just around treeline in a clearing in low brush.  The rain was like a hail of bullets, the clearing was flooded, the wind was unbearable and howling, one tarp blew away, and neither of us slept a wink.  Everything was completely drenched and soaked.  We got up early and hiked several hours to a lean-to that was boarded up with a sign that said closed due to insurance cancellation.  We pulled off enough boards to get in, strung a clothesline, the sun came out, and we unpacked and hung everything up to dry.  We took the rest of the day off, and continued on the next day, staying in shelters for the rest of the trip.  The bivies worked OK in the shelters, though.

” In that case, that Silvertip looks to be an amazing shelter.”

I think it is funny that with the high technology of today, the best tent design we have was created by native Americans long ago.

Would a non-closed bivy, such as MLD’s event soul, still suffer from condensation if the bag remained unzipped throughout the head?

I think that would work, unzip enough to have head totally outside the bivy – no condensation

I would argue that eVent is overkill.  That is waterproof enough it can withstand rain, but if it’s raining I want a tarp or tent.

Something with a good DWR like Momentum 50 is lighter weight and more breathable.

But eVent should work if that’s what’s available.

I suspect this opinion is a bit in the minority, but it’s what works for me.

I’ve tested Momentum 50 – put puddles of water on it overnight.  The puddles are still there 24 hours later.  With some DWR the puddle will stay on top for a while, but will penetrate after a while.  It finds a way through the fabric at which point it quickly drains through.  But even that DWR would probably be good enough, that test might be overkill.

It isn’t just breath that causes the condensation.  The average human loses about 200 ml per 8 hours of sleep between breathing and evaporation through your skin.  It is that latter piece that sometimes is forgotten. Imagine if you are in a really warm sleeping bag and sweat.  That adds even more to the moisture that is emitted.  So between evaporation through your skin (insensible perspiration) and through sweat from being too hot, you can easily wet the inside of a bivy as the moisture moves through your sleeping bag only to cling to the fabric on inside of the bivy.

yeah, but the amount of water from breath is a lot more than insensible perspiration.  Any reasonable material like eVent or a DWR should allow that to pass through.  Just based on data posted here on other threads and my experience.

If you’re so warm that you’re sweating, reduce your insulation.  You could open up the bivy more and move your quilt out of the way, unzip sleeping bag, remove any clothing,…

Of course each person is different and should try different things and do what works for them.

“Would a non-closed bivy, such as MLD’s event soul, still suffer from condensation if the bag remained unzipped throughout the head?”

Even if unzipped, there are certainly circumstances where condensation will occur on or in between surfaces no matter what (due primarily to temperature difference, RH difference, dew point, air velocity, altitude, etc… ) The best thing one can do have a way to manage the condensation when it shows up.

Some bivys (Todd/TegralTex) have the ability to “manage” condensation through their moisture wicking inner lining. But that’ll come at a weight penalty. I’ve been using an ID Salathe bivy since the 90’s with great success. But at 29 ounces I use it for very special circumstances (short trips where sleep space is small, setup time/stealth are critical, weight isn’t a big concern, and when I know the weather is an issue.)

I guess the real question now is would Event/Momentum 50 be breathable enough to address the small stuff like perspiration, humidity(low), altitude, etc. I believe I read somewhere that our breath accounts for 80-90% of that 200ml per 8 hours listed above. If true, that would take a large chunk out of the condensation as a whole if my head/breath was outside of the bag. Interested to see if anyone has experience with the suggested fabrics without there head being inside of the bivy…..

With a snow trench, one should be able to use a bivy without the overhead protection in a problematic situation, which is why I’m curious.

“Of course each person is different and should try different things and do what works for them.”

Indeed.  I tried for years but couldn’t make it work as well as I would have hoped.

“With a snow trench, one should be able to use a bivy without the overhead protection in a problematic situation, which is why I’m curious.”

That’s how I view bivvying now – emergency to 1-2 nights maybe.  I mean, you won’t die using a bivy but for extended trips you ‘may’ have an issue at or below freezing.  But you may not.

I say give it a shot and post your experience!

“I believe I read somewhere that our breath accounts for 80-90% of that 200ml per 8 hours listed above.”

yeah, exactly.

I don’t think outside RH would be much of a factor – nearby lakes or whatever.

Inside my bivy will be humid because of insensible perspiration.  Then, if there’s a temperature difference between inside and outside, humidity will be driven out.  Even if the outside RH is high.  It’s the temperature difference from inside to outside that’s important.

Outside RH would cause condensation on the outside of the bivy.

The biggest thing I’ve noticed is that if it’s clear and the night sky is visible to the outside of my bivy, first the air temperature will go down, because of radiative cooling, until the RH goes up to 100%.  Then the outside of the bivy will further cool from radiative cooling, and then all the outside humidity will condense on the outside of the bivy.  Also, any gear I have next to my like my glasses, flashlight,…

Sometimes, it’s worth it, I like to look at the stars.  Then you have to dry everything off the next day.

Other times I’ll put up my mid and leave the door open so I can see and hear.  There’ll be condensation on the inside of the mid, but not on my bivy or gear next to me.  The tent walls protect me from the radiative cooling.  Or sleeping in an area with tree cover so very little night sky is visible will way reduce condensation.

If the RH is low or if it’s cloudy then there won’t be much if any condensation on the outside of the bivy.

I have never had any condensation inside my bivy even when the outside was wet, because I don’t breath into it.

The medium MLD superlight solo would be pretty good – 7.5 ounces.  Unzip the top so the bivy covers your shoulders and around your neck, but your head is totally outside the bivy.  Wear a hat or balaclava for warmth.

A problem with quilts is it comes up on the edges and cold air gets in.  People talk about getting a wider quilt so it can be tucked in, or straps or whatever, those don’t seem as good a solution as a bivy.  The bivy prevents any drafts around the edges of the quilt.  You could use a small quilt instead of a large one and the weight savings will almost pay for the weight of the bivy.

Again, your mileage may vary…

I used the OR Advanced Bivy and it had the “gator mouth” opening where it could remain open to a certain extent with or without bug net. Condensation really depended on where it was sited, but on the few times it got it bad, I just turned it inside out to dry it.  Climbers use these things.

The big deal is not being able to easily change clothes if all wet and it’s still raining outside.  Thinking an all synthetic system …  with maybe a synthetic puffy jacket/hoody and MYOG warm synthetic elephants foot-quilt could work out.

Also it was a “cozy” set up but cozy is great when it’s colder, not so great when warmer..

Bivy sacks are silly, at best.  Pretty much always another, better, usually lighter solution.

If your Silvertip struggles in wind you either have terrible ground for staking, or the storm is strong enough you’re in for a rough night in anything short of a well built cabin.

I haven’t got a bivy to work well in the rain.  Getting in or out of the bivy while it’s raining is a problem.  And you have to close up the bivy to keep the rain off your face so then you’re breathing into the bivy so you’ll get condensation.

If it’s raining I want a tent, like a mid, so I can sit up and do stuff while it’s raining without getting wet.