Waterproof Breathable Fabric – Explained

OK, wear your vinyl coateed K Mart parka on a moderately paced 1 hour hike first.

Then, after you've dried off after removing the parka and hiking back to the trailhead do the same hike in an eVent or Gore-Tex Pro Shell parka and notice the difference.

Convinced now??

The real problem with these fabrics is that no one lists the hydro static head or a breathability number. They just say waterproof / breathable. So when they go to the store they cannot compare the performance of the fabrics. Some people will therefore sellect the brand they trust or have heard good things about(frequently this means gortex). Others would base there desicion on price and therefor may select a material that is cheeep not very breathable.

The result of this is that people that buy the cheaper stuff are more likely to complain about breathability while people that buy Gortex or Event are more likely to praise the breathability of the fabric.

if manufactures just agreed on one standard test for breath ability and waterproofness and put the numbers on the label the debate would be over very quickly and half of the WPB fabric vendors would be out of business.

How can we have a debate involving Neoshell? it's barely been on the market for 6 months and very few peole have used it enough to know how it compares with other fabrics.

A good read that complements the "Field Testing Air Permeable Waterproof-Breathable Fabric Technologies" series here and addresses lots of questions that come up on the forums a lot, like:
-Does DWR decrease breathability?
-Is the fabric still WP or B once it wets out?

Good pictures of test fixtures too, and explanations of the different technologies.

I've started perusing UKC and signed up for their emails a few months back. They've got some great content.

"The real problem with these fabrics is that no one lists the hydro static head or a breathability number. They just say waterproof / breathable."

The real problem is that the WP and B ratings of a fabric change based on what standard they're tested to (as the article explains), and companies will just list the biggest number they get from a legitimate test. GoreTex is the only brand that seems to hide the numbers and just say "Guaranteed" instead (could be wrong here).

Also, each garment is going to have different fabric (even if the same membrane is used), which affects those numbers. And lastly the construction, fit, and features of the garment play such a large role as well.

Finally read that, thanks eric

couple main points:

"Long gone are the days of bad fabrics and good fabrics. The differences between them are now small, both in the lab and in real use. More important is design, fit, price and environmental impact."

and:

"To get the best possible performance from your waterproof gear there are some basic steps you can take:

• Only wear your waterproofs when it's raining hard. If it's windy then a decent windproof will do the job. Don't wear a hardshell when you're above the cloud line.

• Open the zips! Mountain Hardwear put out a bizarre video about a year ago that claimed that opening pit zips makes you sweatier. That's clearly not true. The argument was that fabrics breathe better when there is a high level of moisture vapour inside the jacket, and that opening zips inhibits this. That is all true. However, if the openings in the jacket are effectively getting rid of the moisture vapour, then you remain comfortable and the fabric doesn't have to work so hard.

• Check your other layers. It's so easy to worry about your waterproof one, yet the crucial ones are the ones next to your skin. That's where comfort matters, not on the inside of your shell.

• If you feel like you're too hot then take some clothing off. It is obvious, but a shell can add a lot to your insulation. Mark Twight outlines his approach in his book Extreme Alpinism and it's simple: wear little under your shell so you're cool when you stop. If you're cold while moving then climb faster! Don't leave the car park wearing four layers so that in ten minutes you melt and have to stop to take some off.

• Look after your clothing: wash it when it needs it and don't leave it to rot in the bottom of a pack. Don't wear it every day of the week then expect it to last ten years; instead save your best kit for when you need it most."

I disagree with their first point – no seperate waterproof and windproof garments – extra weight, not U.L. – not needed

You're most likely in the minority on that last point Jerry.

Many companies do list MVT and HH numbers. Unless you're talking about very thin PU coatings the later always rate far higher than is necessary for rain wear, and it is far from clear if the former generalizes to field usage in any predictable manner.