UKH

Subjective question.

I have a Montane Pac Plus XT which is great, but as I run (walk? Crawl?) hot, i get a fair bit of condensation inside, even with the long pit zips.

Ultimate Lightweight Gear rate the breathability as RET<6

The ME  Soltaro is also paclite goretex and Ultra Light weight Gear rate that as RET<4

Would that difference in breathability make any appreciable difference?

Even the most breathable fabric in the world will get condensation in it when you are working hard. Nothing can handle the amount of moisture we produce 

Well, it works on different principles, but Paramo does a very good job of getting rid of condensation and in my experience, far better than any of the laminated jackets I've had. But I accept, not everyone likes it, and it's too heavy for summer alps.

The tricky thing is that waterproof-breathable fabrics all depend on a temperature gradient to work properly. Simply put, warm moist air wants to travel from a warm place to a cold place. Your body temperature hovers around 37C. The warmer the temperature outside of your jacket and the higher the moisture saturation, the harder it becomes for the fabric to dump your moist air, even with pit zips (actually pit zips are also a strange concept when you realise your body actually dumps most of its heat around the core).

This is why, in my experience and your mileage may vary, any waterproof-breathable material becomes next to useless when the air temperature goes over 17/18 degrees Celsius, and you're just much better off either walking/running yourself dry as it's warm anyway.

My GTX or other laminates only come out of the closet when there's going to be prolonged rain of more than 2-3mm an hour and/or when the temperature is sufficiently low. Otherwise I'll be much happier in a water-resistant layer. 

Yes I've thought of that.

Two questions:

1. What "water resistant layer" would you recommend and

2. How wet does it have to be to make the change from water resistant to waterproof?

To be honest I'm addicted to softshells so I have a lot of stuff to choose from, from a windjacket like the Mountain Equipment Squall that I use in windy weather with just a few drops of rain all the way to a partly waterproof Lundhags jacket that I use in changeable weather. 

I would skip all 'true' softshell jackets as they have become more cumbersome and clammy compared to the new generation of hardshells and go for a single-layer double weave fabric. Something like the Rab Torque or similar. That gives you protection from the wind and some rain. 

Depends on 1) activity; 2) duration of said activity and most importantly 3) the outside temperature.

For my half-hour bike commute I will happily wear a softshell in 2mm-an-hour rain during spring/summer/fall, but when it's winter I will definitely switch to a hardshell in those conditions. For start-stop activities such as ice climbing or winter climbing that's even more pronounced. For multi-day hikes or wild-camping trips I will often only take a hardshell but that's more to do with conditions and space limits in the pack. For gravelling and road biking and other high-cardio activities rain can be a lot more intense before I start wearing a rain jacket, but then those you don't often do in the rain anyway if you can avoid it. 

As a very general rule of thumb I'd say 2-3mm an hour is the maximum of what I find softshells being able to cope with, with a maximum of half an hour. Anything longer or more intense than that and it's waterproof time. 

Thanks for all that - I do have a RAB Borealis which I'm getting mixed messages about whether it's water resistant or not.....

For completeness, the problems that Victor describes are well known by designers and some attempts have been made to try to find magic alternative that don't have the drawbacks above. Mixed results and greatly varied opinions on them.

Gore Tex and alternatives work with a membrane having a with lots of tiny holes that vapour can pass through but droplets typically don't. Impermeable thin plastic film carefully stretched until millions of micro tears start appearing, then bond that inside a layer of fabric

Paramo works by not being waterproof in the membrane/barrier way but wicking outwards. It has a devout following and can be superior for some use cases but is heavier and not ideal for every use

https://www.paramo-clothing.com/en-gb/performancetechnology/

Then there's the left field approach of just don't bother with waterproofs at all. The Sheffield tactic of don't be such a big mardie and just get out there. So clothing aims to be warm when wet instead

https://www.buffalosystems.co.uk/about/

😂 😂 😂

I've used Buffalo many years ago......