too much sweating in homemade electric jacket

To battle the cold in the barn where I spend most of my time, I made an
electric coat this year. While the electronic mechanism is working
great, I am having second thoughts about the material I used and would
appreciate some advice. I had two poly/ fleece jackets that I picked up
fairly cheaply at Walmart. I took the "base" jacket and sewed the wire
onto the outside of it. Then, the final jacket is put on. The final
jacket is also poly-fleece and serves to help retain the heat generated
by the wiring.
The problem I'm having is sweating. It's not much, but very annoying.
I have to turn everything off and then up cold from the small amount of
sweat that was produced. I have enough wire left over to line another
jacket. Instead of fleece this time, what might I use that would be
better? I already don't like the tightness of the fleece and would
prefer something more lose fitting. Something that wouldn't promote as
much sweating and, if it does, dries quickly. I have very thin coaches
jackets in the closet that are mostly nylon or poly outside with a very
thin white cotton lining. I might use one of those as the next
candidate, but welcome any advice. Thank you in advance.