It depends, really.
There's fleece, which usually lets the air pass through, and -some- felt is also soft, but have thicker fibers or something, and less breathable. Minky fabric is the ones with the little bumbs, but that's one of the worst fabrics to sew since it's so slick and it keeps moving
Pretty much any fabric with a backing, like fur, or close knit fibers is going to be hot no matter what, and eventually your own body heat will be trapped in almost anything that isn't sportswear. I'd sugest just going to a fabric store, or some general stores sell fabric, and wrap a piece around your arm and see how warm it gets
