Breathability Of Waterproof Membranes - An Observation

PhaedrusMC

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I rode for four hours in rain last Friday. It was poxy.

I was wearing a wicking base layer, a shitty polyester work shirt, my Dainese D-Stormer jacket (waterproof liner in, thermal liner out), and my Oxford Rain Seal waterproof over-jacket.

When I de-robed, I was bone dry inside - no damp spots anywhere from rain leaking in. Nor was I damp from any sweating.

There was condensation on the inside of the Oxford jacket.

This tells me that:

  • My (Lidl) wicking base layer does actually wick.
  • The proprietary D-Dry waterproof membrane does actually breathe & wick.
  • The outer shell of my D-Stormer jacket does actually breathe & wick.
  • The heat/sweat vapour had clearly only been halted in its path by the non-breathable Oxford over-jacket.
I'm pretty happy with that. :thumb2

I still want a well-vented laminated shell jacket.
 
I've always found D-Dry to be a very good membrane.

Have had a pair of Dainese D-Dry trousers for over 12 years and only recently did the membrane start to fail in a couple of spots.

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Something I've always thought about a wet through breathable jacket - how can the vapour escape if the jacket is covered in water!
 
Something I've always thought about a wet through breathable jacket - how can the vapour escape if the jacket is covered in water!

It cant. The humidity needs to be higher on the inside, than the outside.
 
Waterproof breathable membranes are a daft idea on motorbikes.
 
Goretex outdoor clothing used to be advertised "Waterproof at 60mph on a motorbike"............
 
It cant. The humidity needs to be higher on the inside, than the outside.

It can. The temperature needs to be higher on the inside than the outside. The moisture passing through membrane is then absorbed by the moisture on the outside.
 
I think his point might have been that when the outer fabric is saturated/wetted-out, its ability to pass vapour is then diminished or absent altogether because the pores/holes are now waterlogged, regardless of temp inside the jacket vs outside. Which makes sense to me.

But you reckon the vapour from inside still does pass through the waterlogged pores/holes, to the saturated outside, and is literally absorbed by the water that's soaked into the outer face of the fabric?
 
It does happen but to a negligible extent and can be ignored for all intents and purposes.
 


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