ID and MLD no longer seem to offer full-eVent bivvies.

Online searches don't turn any up either - the closest are eVent-topped.

Anyone know why?

Thanks!

-mox

My guess is durability and weight. Do you really benefit from a heavier, less durable breathable floor. Or are you better off with a lighter, more durable floor that isn't breathable.

RAB and Wild Things used to offer full eVent bivies. Perhaps you can check with them to see if they're still offered.

Mox,

I have a MLD eVent Soul Side Zip top/foot box Bivy from 2008.

As far as I know, MLD never made a "full" eVent bivy with an eVent floor.

I love my bivy, but I don't see how making the floor with eVent would make it better.

I would think that it would be a bad thing because in extremely wet conditions your body weight might create enough pressure to press water through the eVent fabric and into your bivy.

If moisture/water vapor from a body rises then you would want the eVent only at the top portion of the bivy to allow that moisture to pass through the eVent and out of the bivy.

Having the eVent on the floor of the bivy would quickly get dirty from dirt, mud, pine needles, etc....which probably would result in reducing the breathability of the eVent floor and negating any possible benefits from the eVent fabric.

Lastly, given what might be the limited benefits of having an eVent floor, the cost of having a full/all eVent bivy would make the product extremely expensive for little to no benefit in performance.

Anyway, just some thoughts and observations...if I am missing a possible benefit to having an eVent floor, please share your thoughts.

-Tony

Tony,

Great point on the cost of eVent fabric and the potential for loss of breathability due to it getting dirty.

As far as body weight causing enough pressure to allow water seapage through the eVent fabric, I am under the impression that the eVent, despite it's breathability, is actually more waterproof, i.e. higher pressure, than many of the other fabrics used - silnylon being the likely candidate in your bivy and cuben in mine. I may be off on this point though.

Edited by 7sport on 03/23/2012 11:18:58 MDT.

Nathan,

My understanding is that what makes eVent special is that it is waterproof, but more importantly, has good breathability within a certain temperature range.

If memory serves me correctly, freezing temperatures are an issue for eVent.

Again, this is probably all relative....maybe a better statement is that eVent has a better combination of being waterproof and breathable vs. GoreTex?

I have a pair of the 1st generation 2 ply eVent MLD Rain Mitts, which I have used in the rain while using hiking poles.

I can tell you that the pressure/force of my hands gripping my poles forced water through my mitts and my hands were soaked. (Wearing latex gloves inside the mitts really worked well for me).

However, I have since purchased the newer 3 ply eVent that uses different materials for the palm. (Have not had a chance to seam seal them and use them in the rain).

That is the only experience that I have had with eVent "failing", but my usage of the poles makes for an unrealistic expectation for the eVent to work.

If I did not have hiking poles, it is likely that my hands would have remained dry.

As for Cuben, I don't have any experience with Cuben in the rain.

I recently purchased the MLD Cuben Solo/Mini tarp for my setup, but rarely have encountered rain in the Sierras, so I have not had a chance to see its performance in the rain.

How do you like the Cuben floor in your bivy?

I have the old green silnylon 2.0 fabric, which MLD no longer uses, but mine is bomber strong and has never wetted out from use in the rain. (13 hrs of rain at a base camp just below the top of Mt. Whitney with MLD Ponch Tarp and MLD Bivy with crazy strong wind that destroyed other traditional tents. Sold on build quality of MLD).

-Tony

I really like my WT full eVent bivy. Havent noticed any issues w/ it being full eVent. Overall I think its one of the best bivys on the market.

Tony wrote: "How do you like the Cuben floor in your bivy?"

Haven't had this version out in the "field" yet to try the cuben floor, but I can offer a couple of observations:

It feels more durable/substantial than the silnylon version, particularly with respect to punctures.

It also appears to be less packable than the silnylon version. The cuben is just a stiffer material.

Also there are pros and cons of the "slipperiness" of silnylon when it comes to packing. Makes it real easy to slide into a stuff sack, but sometimes is a little difficult to control while rolling or folding.

Wish I could offer more. I'll be getting out there with it soon enough though. Already a couple of trips in the works in the next few months.

I spoke to Evan Jones once @ ID and he told me that the all eVent bivy / overbag was far more breathable than the Micro Bivy with eVent top. I have the overbag and have never had condensation issues with it.

Regarding not working below freezing, it is Epic that doesn't work well as ice forms in the pores. EVent works really well below freezing and would be much preferable to Gortex.

We offer the all 3 Layer eVent Soul Bivy as a custom option. Same price as the stock cuben bottom version!

Ron
MLD

Ron,

Thanks for chiming in on the coversation.

Given your expertise, is there a compelling reason to have an eVent floor in a bivy?

-Tony

Yes, my experience and that of Evan Jones is suspect. ; )

What about that of Ryan Jordan?

http://www.backpackinglight.com/cgi-bin/backpackinglight/integral_designs_event_overbag_micro_bivy.html

The floor of the bivy is sitting against dirt and there will be little air flow under the fabric. Above the floor of the bivy the sleeping bag and pad will be against the fabric and block airflow from above. With no air flow above or below very little water vapor reaches the fabric floor of the bivy and very little of it travels through the fabric floor. furthermore warm moist air will rise to the top of the bivy which keeps it away from the floor. In short making the bottom of the bivy out of event fabric will do little to reduce the humidity inside. The top of bivy the in contrast has maximum air flow on the outside and inside and therefore most of the water vapor will reach to top of the bivy and vent through the top fabric.

Since Event floor cost more and offers no significant breathability or durability benifit over standard waterproof nylon floor, most companies don't use Event, Gortex, or any other high performance breathable fabrics on the floor.

I've got a zpacks groundsheet which uses 1.0oz cuben so MLD's 1.2oz floor should be very strong.

I'm just currently tossing up between this 340g MLD soul eVent bivy VS 600g Rab ascent bivy currently on special at campsaver for $225

For alpine climbing, I feel the extra $100 to shave several hundred grams would be well worth it. Does anyone have more photos or reviews of the MLD bivy?

I would love to hear of experiences of it being used in the rain or pics of it folded up.

"In short making the bottom of the bivy out of event fabric will do little to reduce the humidity inside."

Theory doesn't always make it to reality and you are incorrect. The moisture from your body will condense on non-breathable fabric. In this case, the floor. Using eVent prevents the accumulation of moisture. Even on the floor. And it is significant, especially on snow.

"I found that condensation accumulated on the sidewalls of the 70d nylon floor of the Micro Bivy in very cold and wet conditions. In similar conditions, much less condensation formed on the inside of the Overbag/Bivy."

Edited by FamilyGuy on 03/23/2012 23:47:57 MDT.

Having spent time in a variety of bivys in varying conditions my full eVent ID overbag was the most effective in condensation/moisture management. At least with the ID bivy the full underside is not pressed against the ground. You can also turn the bivy upside down an use it.

Richard, you say its the most effective, but does your bivy still end up slightly damp by the morning?

Another ID eVent overbag fan here.
I've used many bivvy bags over the years made from goretex and always had some condensation, sometimes a lot, on the unbreathable floor.
I've only ever had a touch of dampness inside the all eVent bag.
The drawstring closure isn't a problem, as i use it with a small tarp over the head/torso area.

Maybe the slightest amount of perceptible moisture, but that would be in situations where other bivys would have had visable condensation.