Water repellency rises with garment weight (waterproof-breathable)

Now that you mention it that matches my experience – heavier fabrics are more waterproof.  For example, the Neoshell jacket I made is better than the RSBTR WPB fabric.

Water beads up on the Neoshell where it eventually wets out the RSBTR fabric.  It seems like it’s a surface thing though, but maybe there’s something about the thickness of the fabric.

Now I’m going to have to look for where I can get Pertex Shield Air

I like both the Neoshell (from Discovery Fabrics) – good for steady rain.  and the RSBTR – no or light rain, longer hikes where I want to minimize weight.

My experience tracks with this too. My OR Helium (the newest variant) wets out pretty quick in heavy rain vs my Arcteryx Beta LT hybrid can go multiple days of sustained rain with no hint of failure.

Very interesting. That would explain why some people like their (heavy) GoreTex Pro, and why I’ve never seen DWR last more than half an hour in moderate to heavy rain (because all of my tests have been on light fabrics).

It isn’t intuitive, but it does clarify some of the wide variety of field reports.

I have a very heavy WPB jacket from REI that’s decades old.  Full lining.  It’s pretty waterproof even in steady rain.

Makes sense. I had a OR Helium that wetted out once when it was pretty new. My much older and more abused heavier GoreTex jacket seems more waterproof.

I think this makes sense but would add a caveat. Heavy jackets tend to be stiffer. They probably shed water better because they aren’t plastered to you and even if they wet through a bit it’s less noticeable.

But I still think a heavier fabric should resist wet through more all other things equal. You can make a 9-12 oz jacket with heavy fabric if you keep it simple. Light enough for me.

“Heavy jackets tend to be stiffer. They probably shed water better because they aren’t plastered to you and even if they wet through a bit it’s less noticeable.”

Yeah, that makes sense

Also, stiffer means it’s less likely to catch on a limb that you brush against

“You can make a 9-12 oz jacket with heavy fabric if you keep it simple.”

Yeah.  My Neoshell is 13 ounces but it’s long, big around, has a lining for hood and shoulders so it’s a little heavier than the simplest you could do

I think DWR works with surface tension. Heavier fabrics are more waterproof because they’re thicker and/or denser. My heavier eVent coat can get wetter than a Pertex Shield one I have, but I may feel wet inside the Pertex, even if I’m not. I’d say the thinner Pertex relies a little more on the DWR. I think it will wear equally on both. It’s what’s on the outside that counts.

.. heavier fabrics .. thicker

Thanks for all your responses.  I did a search for backpackers who seek out the rain .. couldn’t find any (lol) but, among others, did find some advice from Outdoor Research about hiking in the rain (probably the old 3 layer system .. long sleeve base, fleece, shell and traditional accessories).  In there was this tidbit about DWR ..

On long trips with constant rain, the outer layer on your hard shells will inevitably wet out. This drastically lowers the fabric’s breathability. But pit zips will never fail

Implies the inner layers (2.5 or 3 layer construction) stay [relatively] dry assuming venting. OR Webpage on this:

https://www.outdoorresearch.com/blogs/stories/10-tips-for-making-rainy-backpacking-way-better

(both links on my posts today work as of 10/1/2023)

I’ve worn my Neoshell for a few hours in constant rain and it never wetted out

I dunno about wearing so much underneath, like an extra fleece layer.  I’ll get sweaty and then wet.  Just base layer and jacket is better.  If it get’s below freezing then maybe I’ll get cold and need a mid layer, but then it’s not raining.

This is a contentious subject, but I think of pit zips as a marketing ploy.  I have one jacket with pit zips and never found that to produce enough ventilation to make much difference.  Opening the front zip provides ventilation if rain isn’t blowing at me from the front.  Or taking my arms out of the sleeves and sort of use it like a poncho.

But, a lot of people find pit zips useful, so it’s something to try.

The current DWR treatments (“C6”) do not work as well as the old ones (“C8”). I think the old ones stopped being used due to environmental concerns. The newer DWR compound, wet-out more quickly than the old C8 stuff. So, it’s not just fabric thickness, it’s also which DWR was used.

I agree with Jerry about the relative uselessness of pit zips. Maybe being on the west coast matters here? Less RH in the mountains? Anyway, by far my most useful rain jacket has been a 3 ply event smock by Rab. This smock has a deep half zip in front but no pit zips and has never wetted out, even in some gnarly conditions.

My pitzips work great… when I don’t have a pack on and the garment can flop around front and back and allow air to circulate.  Pack on…. half of it is pressed against my clothing and I get soaked from either the inside or blowing in from the outside.  If I could just figure out how to hike for a week with a fanny pack.

Pit zips will help regulate body heat. I had pocket zips put on mine. They help ventilate and allow me to reach into my hoodie pockets if I’m wearing one.

A coat that’s adequate walking flat or downhill may be too heavy walking uphill. That’s when ventilation helps.

I’m not arguing that pit zips aren’t good, just identifying factors that would affect sweating and ventilation.  Anyone should try them to see if it works for them.

The cross sectional area of the opening of a pit zip is small.  The fabric gets pushed together so the actual opening is even smaller.  Not very much air flows out.  There isn’t very much ventilation.

If you have a full zipper on the front then you get some ventilation.  You can easily lose half your body heat/vapor.  But rain can blow in and get you wet so this doesn’t always work.

Reducing sweating is the biggest factor.  Reduce insulation until you’re a bit cold.  Slow down so you don’t produce so much body heat which will make you sweat.