I think I practiced what I preach today, the air felt damp, there was a litle bit of very light drizzle at the start, it was overcast and I thought it was rather cold. There was no air movement at all. I decided to wear my cheap (£14.99 when I bought it) single skin Decathlon wind jacket, it's not waterproof but its really effective at what it's designed for. In running terms it's my most used article of clothing.
I wore my Brynge 'string vest' and my long-sleeved bamboo base layer underneath. Within a mile, I knew that my wind jacket was building up its usual perspiration wetness on the inside so I did a full unzip and ran another mile but I could feel the wetness inside my sleeves, the inside of my jacket had dried but not inside my sleeves.
Sometimes I just take the jacket off and tuck it under my belt for the whole of my run but today, without stopping I just took it off, turned it inside out, put it on again and kept running. That did the trick, the whole jacket and the sleeves dried in about a minute. About a mile later, I just turned it inside out again, put it back on and carried on. I soon came to a steepish hill, so I just took the jacket off (I knew how hot and sweaty I would be) and slowly and deliberately plodded on to the top and by then I knew I would keep the jacket off for the rest of my run, I was steaming!
I'd rather do these easy procedures 2 - 3 times on a 4-5 mile run than spend out lots of money on a so-called 'breathable' jacket, for me, it's just not worth it. The ones that testers claim are 'breathable' (I don't believe it!) seem to be over £100 but to me, £50 would be too much to pay as well.
I would go far to suggest that when hiking and I am hot and sweaty the inside wetness is often more of a problem to me than the wetness on the outside, that was definitely the case when I used to use my Paramo Alta 2.
