Field Testing Air Permeable Waterproof-Breathable Fabric Technologies – Part 2: Are There Detectable Differences Under Real World Backpacking Conditions?

[James holden]

im absolutely amazed that no one has commended that the stoic vaporshell tested to the top of the pack … there was quite a bit of controversy on the forums when it came out about its breathability … looks like it might be quite breathable … sure it weights 14 oz …

but they are $90 on sale right now if yr sized large and above … i need a medium unfortunately

when yr paying $90 (or $129 regular price) vs. the same or better performance vs some of these $300+ shells … you have to really ask yourself what are you really getting … ive hear backcountry has a great warranty so it cant be that … hmmm

i think its quite eye opening at what price a good WPB shell with the same performance of "top brands" can sell for once you take out a lot of the marketing and "brand premium"

[Dale Wambaugh]

"It was on sale for next to nothing but I could only get an extra large. I usually wear a medium."

That may be the "bellows effect." I can see how a larger jacket might move some air in and out as the user moves their arms and bends, but I've never seen it tested. That should be simple enough to test: just wear the same jacket in various sizes. If that is a factor, then I wonder how trekking pole use would effect the mix. I would really like to see size tested on non-breathable jackets. Ponchos and windshirt/umbrella mixes should be tested too.

[Stuart R]

Mike said "Everything you are wearing is wet. Continuous rain, even as you pitch your tent/shelter/tarp. You set up your tent, and crawl inside. Your sleeping bag/quilt is dry, because you have used a drybag inside a packliner. You cook your meal inside your shelter. You can't cook outside, as the rain and 50mph wind would cause a slight inconvenience. The steam from your cooking adds to the 100% humidity. All your wet clothing adds to the moist mix in your tent."

That's in summer. In winter it's much the same, but a few degrees either side of freezing.
I always keep a dry set of Helly thermals for wearing in my sleeping bag. In the morning I take them off and put all my wet clothes back on again. They're cold but you soon warm up when you get going. Fleece is great, even if it gets soaking most of the water can be wrung out and then it provides good insulation.

[Andy Davison]

Jeffrey wrote "I feel that the bagginess resulted in less sweating out from inside."

I too have noticed that oversized garments are more comfortable.
I read a PhD thesis (carried out at Leeds University) testing all sorts of shells around a walking route and measuring the temperature and humidity inside, much like the test done here. The author's conclusion was that the spare volume inside the jacket makes a big difference, probably because it creates a reservoir for humidity which takes time to pass through the fabric. This may be more relevant to undulating walks where the humidity created in the short uphill sections is dissipated in the easy sections. It seems to me that baggy garments are likely to allow humidity generated in sweaty areas to move to areas with less humidity and maybe fabric movement pumps air around, too.
I'm curious to know if the XL Montane jacket used in the tests had more volume than the others as this may help explain its excellent performance on the undulating walk?

[Sam Farrington]

About the discussion over WPBs when the DWR fails: I don't know if failure of the outer DWR treatment will allow leakage; but using detergent is not the way to find out. Detergents and many other substances will 'contaminate' the WPB membrane and allow water to come through. I once did this by spraying a silicone spray on an early edition of Danner GTX fabric boots – they leaked so badly just from high, wet grass, it seemed like they were not just failing, but actually attracting the water. This subject was discussed in Alan Dixon's article here:

http://www.backpackinglight.com/cgi-bin/backpackinglight/00316.html

I do know, as several of the above posts point out, that failure of the DWR treatment, and the resulting 'wetting out' of the garment will prevent water vapor from passing through it, and eventually cause the wearer to be soaked with moisture from perspiration in many conditions.

Usually such conditions also carry the greater threat of hypothermia, so being soaked from inside can also be dangerous; in that when you are soaked, heat rapidly disperses. Soaking from outside is probably worse, though, because colder water is continually moving from outside, into and through the garment. That's where I agree with David Ure 100%.

I have had several close calls with hypothermia, the worst being in kayaks on large lakes during very cold rains in the fall. While a GTX pull-over, along with a spray skirt, did keep me from being totally sopped after many hours of paddling in the rain, I eventually reached the point where I knew I was in serious trouble and had to get off the water. The second worst situations occurred when hiking for long periods during such rains on open, unprotected ground. Maybe they were not quite so bad, because the hiking kept me warmer than the paddling did. These experiences led me to the following conclusions:

> To become familiar with and aware of signs of seriously developing hypothermia.

> To get out of the rain and into a dry place immediately when these signs occur, even if this totally bollixes up the trekking/tripping schedule.

> To carry enough well-protected dry clothing and sleeping gear to get into and warm me up in the dry place, even though this means carrying more weight than I would like.

> To consume hot food with lots of carbs as soon as possible.

The above are far more important to me than how good a rain shell is. Please give them your serious consideration. Thanks.

[Roger Caffin]

> I read a PhD thesis (carried out at Leeds University) testing all sorts of shells
> around a walking route and measuring the temperature and humidity inside, much like
> the test done here. The author's conclusion was that the spare volume inside the
> jacket makes a big difference, probably because it creates a reservoir for humidity

In a PhD thesis???? What was the School – Home Economics????
That (the reservoir idea) has got to be among the most stupid suggestions that I have heard. The physics just isn't there.
What a 'spare volume' does is flap! And that pumps a lot of the humid air out. As Dale rightly said.

Cheers

[Mary D]

I've found that a baggy jacket has more ventilation. In addition, I want my rain jacket big enough to wear over my puffy insulating jacket at rest stops and in camp. Life gets very difficult (and can be threatened) if you can't keep your insulation dry!

I still can't determine enough difference between a "breathable" jacket and a non-breathable jacket to warrant spending the big bucks for the former! And I've had too much expensive Goretex fail where the shoulder straps rub it. If temps are warm, both types of jacket get equally wet inside. I just leave the rain gear off when it's warm and get wet; my baselayer top and hiking pants will dry on my body in 20 minutes. If it's cold, it doesn't seem to matter either.

I do find that pit zips help a little. Leaving the front zipper part-way open helps a lot more. Of course if the rain is coming horizontally from the front, I have to close the front zipper, but usually under those conditions I don't get hot inside!

Thanks for the article, Will! It has confirmed my own experience (or, if you prefer, prejudice) that there is little difference, or at least not enough to be worth the extra money for those "miracle" fabrics.

[Andy Davison]

Quite right, flapping has got to be a big factor, but how much moisture is moved out depends how well the garment is sealed and how much movement there is. I imagine a sack would seal the body of the Montane jacket pretty well, or does the neck closure create a large chimney?
As far as I'm aware the tests I mentioned included Paramo and Buffalo, both of which trap air between the layers and may be less effected by flapping…the PhD (actually it could have been a Masters) was in outdoor clothing or sports clothing, I'm not quite sure of the title.

[James holden]

gore i believe requires their active shell be quite form fitting … the reasoning was that the less dead air the higher the "breathability"

[Andy Davison]

Thanks Eric, I wasn't aware of that. As far as I understand it the rate of breathability will increase when the difference between the inside and outside vapour pressures is greater, so high humidity on the inside should increase the rate of exchange. Also, if the shell is closer to the body it should be warmer, reducing the chances of condensation for a given humidity. But maybe the other reason is just to save weight in the garment?!
Despite all the above, evaporating 100ml of sweat into 1 litre of dry air is going to generate twice the humidity of putting it into 2 litres (though the moisture vapour transfer rate may be higher in the latter case).

[Jason Elsworth]

A light (8.5 oz) tight fitting fleece is usually in my 3 season kit here in NZ. If I don't need it when walking (and I usually don't) then it is great to take off a wet base layer and put it on. I don't like being too reliant on walking at a brisk pace to keep warm, as difficult terrain, tough descents and navigational challenges can often make this impractical. It may go against UL dogma, but it's my insurance.

I would really like to try the Paramo system, but it is expensive, so I will probably stick with an eVent set up that can be used year round. I am also considering moving away from merino base layers to something a bit quicker drying. Recently a combination of light softshell trousers and eVnet over trousers worked really well for my legs. It made me wonder how well a light sofshell jacket (like the RAB alpine) would do under a hardshell in cold, wet weather.

[Manuel Espejo]

I usually hike in the Paramo ecosystems near my home in Villamaria, normally don't rain a lot up there, but is high and is the tropic, sometimes the humidity can be 90% or higher, so is imposible to stay dry. I use a lot of systems from windshirt + umbrella system, WPB Jackets, Silnylon ponchos and Paramo waterproofs. with all the systems I become wet in serious rain or with high humidity (a lot of fog. so I prefer the Paramo systems. Yes, at the end I become wet but warm and the garments take little time to dry and is easy to bushwack because there is not a lot of trails here. the only drawback of Paramo clothing is "too warm" for most of the conditions.

P.D: the new formula of Nikwax DWR is more durable.

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