I've been experimenting running with my different layers while running to test breathability and managing my temperature. I've worn both fleeces and softshells while running in around 30 degree temps, and I felt they made me overheat and sweat somewhat during my runs.
So today I wore my Marmot Essence jacket, made of Marmot's proprietary fabric that is supposed to be almost breathable as eVent but is super light (< half pound). It was kinda ...