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Just Tom
01-10-2017, 10:28
I have not had the greatest luck using a MLD superlight bivy in various scenarios. I know condensation is an issue with bivies, but as a non-waterproof model I had hoped it would breathe well enough. But I used it this past weekend and when I awoke in the wee hours of the morning to heed nature's call, I unzipped and pulled back the top to discover a lot of moisture. It was pretty cold (15 degrees) so i expected moisture to condense, but I thought it would happen after the vapor passed through the top material. That is kind of the point of why I was using it (that and the fact I was in a floorless shelter). Do I need more heat (say, hot water bottles) to drive the vapor fully out? Or maybe something to catch my breath so that moisture doesn't contribute to the problem? Something else? I'd really like to make this piece of gear work, so any tips or advice is welcome.

MuddyWaters
01-10-2017, 10:49
Put a 1-2 ft wide mesh panel down the top
Problem will be mostly solved..on top.

Seriously, several bloggers have done this. Im surprised ron doesnt offer it as standard option.

Youre discovering why bivys suck in humid environments.

And why i use only a bug bivy, mesh top.

Just Tom
01-10-2017, 10:56
I've given up using it in the summer for splash protection, but the air doesn't really have much humidity at 14 degrees, I don't think? I kind of assumed I was the source of the moisture.

I have a bug bivy, but it doesn't protect the footbox of my sleeping bag from rubbing against the shelter wall. Maybe I just need to make a small cover mini bivy just for the foot end and skip the rest?

MuddyWaters
01-10-2017, 11:01
I've given up using it in the summer for splash protection, but the air doesn't really have much humidity at 14 degrees, I don't think? I kind of assumed I was the source of the moisture.

I have a bug bivy, but it doesn't protect the footbox of my sleeping bag from rubbing against the shelter wall. Maybe I just need to make a small cover mini bivy just for the foot end and skip the rest?

All it takes is moisture in warmer bivy air, and fabric below dewpoint...which you got. The moisture comes from your skins respiration. You could use vapor barrier, then youll be damp instead of bag and bivy

English Stu
01-10-2017, 11:21
With the Superlight if I notice dampness is happening, or may happen, or it will be too warm with it I unzip as much as possible and use it just to keep the foot of the bag from picking up moisture from the tent side. I have a TT Notch. I like the Superlight as a piece of kit; it gives you the option of cowboy camping if it is fine.

Slo-go'en
01-10-2017, 14:41
If most of the wetness was near the head, its your breath which is the problem. If you pull the shell up over your head, that will do it. You need to keep your head outside the bivy, which is easier said then done with most designs.

Tinker
01-10-2017, 16:47
I had the same bivy - same problem. Tried other bivies - same problem. Bought a Hilleberg Akto - no problem. Moisture was still there, but at least it was on the inside of the tent. Getting in and out of the tent dry was another issue, entirely! For me, a bivy is a piece of emergency equipment, when I don't expect to spend a night out. I've even experienced heavy condensation on the underside of a tarp in a hammock in winter weather!

Slo-go'en
01-11-2017, 03:13
I have an OR "Advanced" Bivy (2008 model) which I typically use in the fall when I know it's probably not going to rain, but I want some protection and extra warmth. It actually weights more then my tent, but is easier to set up on tent platforms and in small spaces. It has a Gortex top, hoops to keep the front off the head and netting. I've not had excessive moisture build up with it, even when I have to button it up pretty tight. It got covered in frost the last time I used it, but inside stayed dry. My head area which was exposed did get a little wet due to the frost and my breath. No big deal since it was just an overnighter.

Slo-go'en
01-11-2017, 03:28
Okay, I looked at the bivy and can see why it can have condensation problems. If you don't have the full head net option, it would be real easy to breath into the sack when it's cold, especially if your a side/stomach sleeper so your mouth isn't aligned with the ventilation hole. Try not to seal yourself into it if you don't have to.

saltysack
01-11-2017, 09:05
I've given up using it in the summer for splash protection, but the air doesn't really have much humidity at 14 degrees, I don't think? I kind of assumed I was the source of the moisture.

I have a bug bivy, but it doesn't protect the footbox of my sleeping bag from rubbing against the shelter wall. Maybe I just need to make a small cover mini bivy just for the foot end and skip the rest?

I've had good luck using my zipped up rain shell over the foot box of my quilt to keep it dry, and also used my compactor bag that I line my pack with as wanted to wear rain jacket.Don't think the compactor bag would be good in east coast as doesn't breathe...


Sent from my iPhone using Tapatalk

Just Tom
01-11-2017, 10:29
Okay, I looked at the bivy and can see why it can have condensation problems. If you don't have the full head net option, it would be real easy to breath into the sack when it's cold, especially if your a side/stomach sleeper so your mouth isn't aligned with the ventilation hole. Try not to seal yourself into it if you don't have to.

Actually I do have the net hood version. But still, the condensation from me breath has to go somewhere, and I think it is getting sopped up by my sleeping bag (well, quilt really, but that doesn't matter). I had hoped it would condense on the outside of the bivy, but I think in reality it is immediately hitting the bag since it isn't like I've got the edge of the bivy top material tucked under my chin.

That all being said, the moisture was not 6 inches at the head end, but maybe the whole torso. So the moisture is either wicking from the head via capilary action between bag and bivy, or the moisture is getting evaporated from my body heat and then trapped in the torso area maybe?

Thanks for the feedback!

Just Tom
01-11-2017, 10:31
I've had good luck using my zipped up rain shell over the foot box of my quilt to keep it dry, and also used my compactor bag that I line my pack with as wanted to wear rain jacket.Don't think the compactor bag would be good in east coast as doesn't breathe...


Sent from my iPhone using Tapatalk

Hmm, I like that idea of using the rail jacket in cases where I'm not needing the bivy for any other reason. (In this case, I was hoping for some extra warmth, but many times that is not the case).

Slo-go'en
01-11-2017, 13:21
That all being said, the moisture was not 6 inches at the head end, but maybe the whole torso. So the moisture is either wicking from the head via capilary action between bag and bivy, or the moisture is getting evaporated from my body heat and then trapped in the torso area maybe?

Thanks for the feedback!

The only way to know for sure would be to try again in similar conditions with the top of the bivy rolled back below your head so there is no chance of breathing into it. Unless your so warm your sweating like crazy inside the bag, I doubt you loose enough water via the torso, which then has to make it's way through your bag, to have significant condensation inside the bivy.