By the Numbers: the Search for a High-MVTR Waterproof Breathable Shell Jacket

[Stephen Seeber]

Ben: Obviously, it is pretty difficult to figure out what happened since the jacket is gone. On the other hand, you are a very experienced backpacker and would have a good sense of when a piece of gear is failing.  Unless the wind was blowing pretty hard, even with a wetted out jacket, water should not have come through if the membrane performed at >10000 mmwc.  Maybe it did leak.  How much use did that jacket have?  Was your base layer soaked or were you just cold.  The wetted out jacket would increase your rate of heat loss.  You didn’t say how wet your base layer was, but would you say you were working hard enough to wet out your base layer with sweat?  My Neoshell jacket has only seen winter use, so no time spent in the rain.  My Neoshell pants would let water through if I went sliding on the snow.  Getting water through my Neoshell pants was an ongoing issue and I eventually retired them, maybe 4  years ago.  I still have them.  So, I just went to where they are stored, took them out and inspected them by holding them up to a light.  I found decent size areas where a lot of light was coming through.  I placed one of those areas on the HH tester and started pumping it up and immediately a large amount of water ran through the area.  I checked another area that had no obvious failure.  At 1687 mmwc there were numerous bubbles coming through the surface.  I think it is safe to say this Neoshell has failed.  Those pants had a fair amount of winter use for hiking and snowshoeing and clearly were worn by the use.  By comparison, the Gore-tex pants I replaced them with have many more hiking and snowshoeing miles and several seasons of ski runs on them and have never leaked.  So, if no wind was blowing and you weren’t working hard enough to wet things out, I have to wonder if 1) the jacket was worn due to use or 2) the membrane was defective.  Perhaps other people can weigh in with their experience with the durability and water resistance of Ascentshell, Neoshell and Future Light.

[Jerry Adams]

from the restoring silnylon thread

https://www.versaperm.com/materials/Silicone%20and%20vapour%20permeability.php

“It is an excellent barrier against liquids, but many vapours – such as oxygen, water vapour and hydrogen can pass through most types of silicone almost as if it was not there.”

of course that’s qualitative, but, you’d think maybe silnylon would be good as a WPB jacket

except, in my limited experience I have heavy condensation with silnylon

I wonder what it’s MVTR would be

[Stephen Seeber]

Hi Jerry: I am happy to find out.  Do you have anything lying around you think could be a good test case?  If so, PM me and I can give you an address and dimensions that I need.

[Jerry Adams]

sure, I’ll send you a piece.  I just got some from RSBTR recently.  I think its MTN silnylon, but I just weighed it and it was 0.86 oz/yd2.  Their current version is 1.5 oz/yd2.  Must be a previous version?

I’ll see if I have a silpoly too.

[Brett Peugh]

Hello Stephen,

 

Thank you for this article and all the work you do.

You had said you had tested previous AscentShell jackets.  Is it possible if you could provide models and MVTR?  I know the Interstellar had a 20D while the Guardian had a 50D so I suspect the Interstellar had a lower MTVR.

I tried out an OR Motive but the lack of full cuff closure and a really wonky hood did not did it for me.  Nor does it have any pit zips or other ways to vent other than the front zip.  The inside fabric is nice to the touch though.

I did find an original OR Guardian with AcentShell which has a 50d face fabric so maybe that will have similar MTVR as the Motive as that has a 50d also.  It is only slightly more in weight but has pit zips and vented pockets.  I have always thought direct venting options are of a great benefit and Ryan Jordan’s article reinforced that for me.

I have not had a great chance to full check out the jacket in long and heavy rain yet but it worries me that there are quite a few reviews out there for the AscentShell fabric where it did wet out fast and did leak.  I did read a number or articles about the Marmot Eco Precip that were also similar. I will try to get a Eco Precip also and see if there is much difference between the two.

 

As I am a XXL or XLT I am quite limited in the choices I have available to me so it is nice to see that I have a few options in the upper tier.

 

 

[Tim Hawthorne]

Great testing and article.  I have a question about the Arcteryx Norvan  SL.  I love mine.  If carrying a heavy pack or bushwhacking, I wear a Houdini wind jacket over the Norvan for extra protection.  I assume that the outer wind jacket may increase the MVTR?

I also did not see any test for eVent.  I use eVent glove shells that don’t make my hands feel damp.

[Bryan Bihlmaier]

I’ll add my vote to the request for a test of MVTR for dry vs wetted-out fabric, @stephen. You don’t need a very old jacket to be able to wet out the face fabric – just spray the faucet or shower head on it for more than a minute, in my experience. I would say I take better care of my WPB garments than most people, including futilely to restore / reapply the DWR, but never to any effect. Yes, a drop of water placed on the surface might bead, but poke it with your finger, let it sit for 5 mins, or use a faucet, and there will be no contact angle between the droplet and the fabric – on its way to being absorbed.

[Scott Emmens]

Hi again Stephen, I did listen to the podcast, twice at the weekend but I still don’t understand why a microporous membrane can have a significantly higher MVTR than a tightly woven, or even loosely woven wind shirt fabric. Aren’t the holes much bigger than a microporous holes in a membrane? Why is the MVTR of Shakedry 3360 and the MVTR of the Patagonia Houdini 2250? Is it something to do with the difference between vapour pressure and air pressure?

I now understand about the air permeability and lack of air movement through fabric when it is being worn, that was an interesting revelation which had been hiding in plain sight the whole time.

Thanks, Scott

[Stephen Seeber]

Hi Brett: Here are the 2019 MVTR results you requested: TNF Futurelight Flight-2780; Neoshell fabric-2940, Mountain Equip Arclight (2015)-3060; OR Skyward II-3060.  After Ben Kilbourne’s post, above, I share your and his concern about the performance of Ascentshell.  I hope there are others out there who can respond with any experience they have with that fabric.  I just retested my Mountain Equip Arclight.  It has two more ski seasons on it.  Visual inspection shows a couple of small holes in the fabric.  Another spot tested similarly to the value posted above.  A 3rd area  had a persistent drop that appeared at around 2800 mmwc and another area where numerous small drops appeared at 5243 mmwc.  I actually retired that jacket at the end of ski season last year.  That jacket has seven years of heavy winter use.  I will be testing 4 different Neoshell fabrics shortly but that will not get to the issue of durability for these fabrics.

[Stephen Seeber]

Hi Scott:

Here is a photomicrograph of a Houdini.

Here is a Houdini Air:

You can readily see the additional gaps in the weave that render the Air more air permeable.

I think you need to wonder how much open space, comparatively, a water vapor molecule would encounter from a microporous membrane vs a woven fabric. I suspect that to a water vapor molecule that is much smaller than the holes in the microporous membrane that the water vapor molecule actually sees more open space than in the woven fabric.

The Houdini Air MVTR is  3120, so not that far from Shakedry.  My studies demonstrate that there is a correlation between Air Permeability and MVTR in that as Air Permeability increases, so does MVTR.  You can see it in these two fabrics.  But, let’s not confuse the difference in the ability of MVTR vs Air Permeability to remove moisture.  My studies have clearly shown that MVTR is more important at hiking speeds than Air Permeability.

So, I don’t think I have provided the authoritative answer to your question, but I hope I have a presented a way to think about the mechanisms involved.

[Scott Emmens]

Thanks Stephen, so if I am understanding what you are saying correctly, there are more microporous holes in a membrane for the vapour to escape through than there are in the above fabrics? So even though it appears that the holes are bigger in the woven fabric, the sheer number of microporous holes in a membrane are the reason that some membranes have a higher MVTR?

 

I do feel that I have my head around the difference between air permeability and MVTR and that higher air permeability doesn’t equate to removing more moisture, I too have experienced this over the past year of experimenting with garments.

Cheers, Scott

[Adventure Muffin]

Jerry, I dont have access to the full article, but curious if you tested Frog Toggs?  Material claims a waterproof rating of 8000MM and an breathability rating of 3,000 MVTR.   At 20-25 bucks for a pair of rain pants, will last about one season, and have been happy with its lightweight (0.4 lbs) and waterproof/windproof performance

[Indrit S]

Hi Stephen,

just wanted to understand what a 10k mmwc really means (I’m referring to the ascentshell in the table ), how that translates to the real world usage? Should be expected to leak? Under which conditions exactly?

Btw, I have collected the following data from your previous tests (maybe a couple of years ago) where AscentShell is reported to be around 16k mmwc, does this mean that they control the impermeability of the membrane in base of the jacket/product? Or is this due to recalibration or something ?

AscentShell  MVTR is 3060, HH 16170

Futurelight MVTR 2780, HH 16416

Gore Pro: MVTR 2869,  HH of >30000

Thank you very much for the eye opening article.

[Stephen Seeber]

Easy answer first.  The HH instrument that I have used over the years was claimed by its manufacturer to meet the requirements of the relevant test standards.  It turned out that the reservoir and clamp diameter were undersized.  This resulted in elevated HH readings.  Towards the end of 2020 I had a machine shop produce new, properly sized components.  Now, all readings will be lower than produced on the original device.  Unfortunately, the variance is very much fabric specific so there is no way to correct the older readings.

My personal experience is that 10000 mmwc should be adequate for most activities.  I have found for high pressure uses, such as kneeling in a puddle, water might come through.  I have experienced leaks sliding on snow numerous times with Neoshell.  Also, very high winds will increase the pressure on the membrane and could require higher HH to remain water proof.  Normally, I run the test to 16000mm.  In the case of the Ascentshell jacket, I stopped the test at their claimed performance because I did not want to risk damaging a garment that I intended to return.  Readers who have used electrospun WPB jackets are encouraged to post their experience with this technology.

[Stumphges]

Jerry, if you send samples of silnylon to Steve, you might want to take care that they have 100% silicone coating. All but one of the sil-coated fabrics at RBTR currently actually have blended sil/PU coatings. The exception is 30d MTN silnylon, which they advertise as having 100% silicone coating.

[Tim Hawthorne]

Hi Stephen.  Have you ever or could you test a layer of say Houdini fabric over a Norvan SL.  Opinions exist amongst engineers that I backpack with whether an outer layer would improve the MVTR or reduce it?

[Stephen Seeber]

Hi Tim:  Everything you put between any  layer and the environment adds more resistance to MVTR.  What you want to do would reduce it.  For a better feel for this, see table 4 in this article.

[Tim Hawthorne]

Thanks Stephen:  I was impressed by all of your testing including Table 4.  And that reinforces my thinking a few years ago.  I have some materials science and engineering friends who believe that a wicking porous material outside the membrane could possibly enhance the evaporation rates.  The increased surface area of a highly porous material could act as a catalyst.  Thus air has a larger contact area with the moisture.

You might relate it to wind blowing across a lake and causing evaporation.  If you make the lake bigger given the same wind, the evaporation increases.   I have noticed over the years that my rain gear feels less clammy when it is windy, kind of like a tent stays dryer inside on windy nights.  Does your test equipment account for wind evaporation?

In addition, we have discussed that different materials can affect the surface tension of water droplets passing through the fibers.  Water clings to some fibers more than others.  So if the outer materials create a lower surface tension they will release moisture at a faster rate.  You could relate this to climbing on a wet muddy surface versus a dry knobby surface. You can hold on to one surface less than the other.  Things people talk about around the campfire?

[Roger Caffin]

a wicking porous material outside the membrane could possibly enhance the evaporation rates.
While adding a couple of kilos weight in the rain.

Cheers

[Tim Hawthorne]

Hi Roger: these guys who work for major companies in this business are thinking very thin layers of material that absorb very small amounts of water.  They mostly wick but absorb little.

[Stephen Seeber]

Putting a fragile fabric layer on the outside of  a hard shell would present durability issues and, ditto Roger’s point.   If there is enough wind to make such a thing work, the MVTR of the outer layer would go up due to the reduced MVTR of the air layer outside the jacket. So, the fabric probably would not add anything.   In any case, what is coming out of the shell would be vapor and would go right through a wicking layer.  If the wicking layer were below dew point, than ditto Roger’s point.

[Roger Caffin]

If the layer is that thin, it won’t be very effective at wicking.
A new brilliant breakthrough every couple of years.
But none of them so far have ever worked in the field.

Yeah, so I am old and cynical. And experienced.

Cheers

[Tim Hawthorne]

Stephen: Have you tested a layer of Houdini over the Shakedry?  I have used that combination for bushwhacking for about three years with good success.  The Houdini has held up well unless we encounter cats claw, devils club, cactus or sharp rocks.  I have not noted the clamminess in this combination like on my other Goretex?

I was also suggesting a wind across the surface test to determine what that effect might have.

Of note Polyester absorbs about 0.04% moisture and is very wicking.  I have designed wicking drains to dry up swamps, wetlands and mine tailing deposits with great success.  We used polyester fibers for wicking and blew air into the holes to enhance evaporation rates

I may not be as old, cynical and experienced as Caffin.  I am just a retired engineer backpacker in my  mid 70s with a couple of  questions.

[Jay Lawrence]

Why does the Gore-Tex website say that their Infinium membrane (previously Windstopper) is NOT WATERPROOF??

https://www.gore-tex.com/technology/infinium

This article tested an Infinium jacket and showed that it IS waterproof.

I’d like to buy the Montbell Rain Trekker, which uses Infinium, and is highly rated by this Greenbelly article:

https://www.greenbelly.co/pages/best-lightweight-rain-jackets

Does anyone here have experience with the Montbell Rain Trekker?

 

[Stephen Seeber]

Only Gore can answer that.  For years they did not permit seam sealing with Windstopper, which meant that it could leak.  The Montbell Versalite has sealed seams.  It is waterproof.  I have tested HH to be greater than 20000mmwc.  I have also tested other Windstopper garments.  The fabric is waterproof.  I have not tested the Rain Trekker, but it should perform like the Visp.

[Author]

Posts