Originally Posted by
Doug64
Something I have learned about breathable fabrics as a ski patroller, mountaineer, and bike tourist in the rainy Northwest is the condition of the outer fabric layer is very important. Breathable fabrics depend on the difference in vapor pressure inside the garment and the outside to "breathe". If the outer fabric does not bead up the water, and lets it soak into the outer fabric, it can't breathe. the water layer on the outer fabric acts as a pretty substantial barrier. Keeping the outside of the garment clean and treated with a water repellent product such as "ReviveX" keeps it working as designed-well almost.
Exactly my understanding as well. The earlier statement about breathable fabrics working better in cold weather reflects this, too. Colder air means lower relative humidity, so the moisture moves out better. The fabric can also "wet out" from the inside from perspiration, sealing up the pores and turning it into a plastic bag. In extreme cold, this interior moisture can freeze and then you've really got a mess.
I only use a breathable coat in dry (and clean) conditions, when I'm not working too hard, and brief showers may be expected, like most of the time in the Rockies. Otherwise, I save my money and use cheap non-breathable garments. That's what I'll be carrying on my X-C tour this summer. The comments about staying warm and wet are spot-on for me, too.