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Yesterday I was shopping for breathable waterproof boots* and this is what the salesperson explained to me. The shoe material does NOT matter. The damp air from the foot goes through the membrane (Gore-Tex) to an intermediate "pocket" between the membrane and the outside shell of the shoe. Once the shoe is removed, the dampness begins flowing back through the membrane and into the air, thus drying the shoe.

Is this correct? Do shoes not breathe through the outer layer at all?

* - I call 'boots' any shoes, that are high enough to support the ankle, but mainly leather ones

  • What material was the outer layer made of? Leather or synthetic? – user2766 Mar 12 '15 at 9:20
  • @Liam, we were comparing leather and textile. The salesperson explained that leather keeps much warmer, but has no effect on breathability or water proof-ness. – Vorac Mar 12 '15 at 9:23
  • He might be right for new boot. After a time (My guess - a couple of weeks of use), I would back quality leather as being more waterproof than goretex + fabric. – user5330 Mar 12 '15 at 22:46
  • But the leathers job isn't to be waterproof in a goretex boot, that's the goretex's job, so the leather is simply a protective covering of the waterproof layer, so I'd choose breathability over waterproofness (of a goretex boot anyway). Or simply a leather boot with no goretex – user2766 Mar 13 '15 at 10:54
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    The sale person seems to be describing how Sorel (and similar pac boots) boots work, except that he left out the part about removing the liner every night to dry. Leather & Goretex boots will most certainly dry during use. – Pepi Mar 13 '15 at 10:59
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The salesperson explained that leather keeps much warmer, but has no effect on breathability or water proof-ness

Well he's not really correct there, so breathability is based no the concept that moisture will pass from a high saturation of moisture (next to your skin) to a low saturation of moisture (the outside). The temperature is also important, the high saturation area needs ot be a higher temperature to the outer (that's what the DWR helps with in a goretex jacket)

The Goretex material facilitates these process with pores that that allow water (in the correct state) out but not in. So if the water is trapped inside to the goretex layer (i.e by the outer fabric) this will obviously lower the ability of the moisture to pass though the goretex layer and therefore make the boot less breathable.

Leather is not as breathable as fabric. Air/moisture, etc. does not pass though leather as well as fabric. It is breathable but not as breathable.

If there was a

"pocket" between the membrane and the outside shell,

which I don't think it does, this is going to become saturated fast, and if it's saturated your boot won't breath. This is what a vapour barrier is but that works totally different to a breathable shoe.

So I would suggest that breathability is going to be better in fabric boots than leather ones. That said, he is correct that leather is warmer, so it's a a balancing act, warmth vs breathability. How much this is effected is debatable but it will have an effect.

He is correct that the outer has little input into the water proofoness of a gore text boot, that's what the goretex layer does. Obviously none goretex boots are different.

TL/DR; he was making it up...

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    Importantly once the outside fabric of the boot is wet through (as opposed to water beading up and running off) , it will not breath. – user5330 Mar 12 '15 at 22:39
  • That's not entirely true, it won't breath as well your correct but it should still breath. The DWR is there to keep the moisture from cooling the goretex layer, not to keep the moisture out of the holes as you might expect. That's because an important part of the breathability is the temperature gradient between the outside and the inside. So the indside needs to be warmer than the outside. This is less of an issue with boots than it is with clothing. So the DWR is less important – user2766 Mar 13 '15 at 9:22
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    "special funnel shaped holes that allow water out but not in." I'm impressed, I didn't know WL Gore got Maxwell's Demon to work for them. – Pepi Mar 13 '15 at 10:46
  • I'm likely simplifying @Pepi :) That's how it's shown on Goretex diagrams. I'm sure it's more complicated than that. I believe it has to do with the temperature of the water and therefore how gaseous it is. – user2766 Mar 13 '15 at 10:51
  • @Liam: Once the DWR is gone - with boots, about a 30 seconds walking though wet grass, the vapor pressure on the outside of the Goretex is so close to the inside the amount of vapor passing through the Goretex is negligible compared to the amount of vapour a foot produces. SO we are both right - yes it does still breath, but not enough to make a difference. – user5330 Mar 14 '15 at 0:28
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Goretex does two things well.

  1. It's a very light completely windproof layer.

  2. Properly cared for it's waterproof.

There are many places it's used where it's completely inappropriate and just adds cost. In my experience boots are one of those places.

Goretex only "breathes" when there is a significant difference in the moisture content on one side of the barrier verse the other. That's why it breathes best in cold dry conditions. If it's 100% humidity (i.e. raining ) it's not going to breathe much if at all, if the DWR fails and the jacket wets out, it doesn't breathe at all.

Goretex in a boot doesn't have much going for it. It's generally put in as a "sock" layer behind the inner lining of the boot. This means the layer behind it is not exposed to the cold dry air, but whatever the outside of the boot is. At best the moisture vapor will just go through the barrier and condense on the inside of the boot. All the Goretex is doing is slowing down the drying time of the boot and acting as a vapor barrier to keep your feet wet longer.

In terms of keeping outside moisture out, by the time it gets to the Goretex layer it's too late. The boot is wet and as it drys out, the moisture vapor can go IN just as well as out.

You can get all of the advantages of Goretex in a boot when it works well by getting Goretex socks. These are vapor barrier socks made with Goretex, you can use them when it makes sense and not use them the 90% of the time when Goretex in a boot makes no sense. Here's one example.

http://www.rei.com/product/875635/showers-pass-crosspoint-waterproof-bike-socks-mens

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    I agree with 90% of this, but if the boot is made well and the outer is made of the correct fabric (leather likely not being that fabric) with the correct areas (such as the tounge) being thin enough to allow moisture to pass though it, the goretex layer should breath. This is the same principle that jackets work on, the outer is a protective layer for the gortex and allows moisture though it. – user2766 Mar 12 '15 at 16:31
  • @Liam - Unlike raincoats, the DWR in boots does not last very long. Once the DWR is gone (and the boot is wet), the fabric saturates and the goretex cannot breath. – user5330 Mar 12 '15 at 22:53
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    Goretex gives a water proof boot that breaths when the boot is dry. When dry, a fabric boot is better, when wet, quality leather is better (after the first few few use - first few weeks the Goretex is more water proof). However, if you want one pair of boots that does everything well enough, they have an advantage. My 'front country' boots are Goretex, but my remote back country boots are leather. – user5330 Mar 12 '15 at 22:58
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    An additional reason for avoiding membranes in boots is durability. I know someone who works in this field and in his view delicate membranes don't hold up well to the battering they get in footwear. Once they are compromised by wear, you get all of the disadvantages and none of the supposed advantages. In my experience membranes in footwear don't work for anything remotely serious. None of the best writers on hiking and trekking recommend them. – Tullochgorum Apr 5 '15 at 12:30

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