I bought a Marmot Chinook in August. The fabric label says "100% polyester", and the weight is around 3.7 oz for men's large.
The Chinook performed well in the Colorado Rockies in August, with very little condensation even when
climbing steep hills. The humidity was low and the temperatures were mild (high 40's and above).
More recently I have used the Chinook to go jogging when conditions were around 30 degrees, with moderate humidity. To my displeasure, the inside of jacket was lined with water droplets
at the end of the jog, especially the middle of the back. In comparison, my nike sweatpants, which are probably made of supplex nylon, were very slightly damp but had no condensation whatsoever.
I was intrigued by the difference in performance between the Chinook at higher and lower temperatures, and by the difference between the Chinook and the nike sweatpants, so I ran a simple
experiment. I placed a water droplet on the inside of the fabric, and measured the time it took to disperse. For the nike sweatpants, the drop rapidly dispersed and was no longer visible after a second or so. For the Chinook sweatshirt,
the water droplet stayed put and did not disperse.
To summarize, I think that the Chinook does a good
job of transmitting water vapor but a poor job of
dispersing liquid water. Hence it has good breathability at high temperatures but poor breathability around freezing. Overall, its breathability is inferior to a cheap nike jogging suit, though it may be slightly more windproof.
If you wear this jacket around 30 degrees, there's a good chance that your base layer will be soaked by the water droplets accumulating on the inner fabric. Given that Marmot specifically advertise the Chinook as a highly breathable garment designed for aerobic activities, I think that they should be excoriated for the poor performance of their fabric.
Does anyone know whether the DWR is applied to both sides of the material, or only to the outside? If it is applied to the inside then it would actually inhibit breathability at lower temperatures, because it would cause water droplets to bead up rather than disperse.