Originally Posted by NoRacer
IMHO, if you are going to decrease layers, I'd get rid of the cotton first, because it's nothing but a moisture sponge--soaks it up and holds it.
For an unlined windbreaker, you could try placing some re-enforced tape (like a shipping tape) on the inside shoulder blade areas and then use a razor blade to cut .5 to 1 inch slits within the taped area. You'll still be guarded by the wind, but you will provide a way for excess moisture to escape.
This is a good idea and I might try it with an old windbreaker. I've been a little frustrated because it's been cold enough in the mornings that I've wanted frontal wind blockage, but then I get too hot on my back. I saw some specially design gear at the shop addressing this problem, but didn't want to part with that much cash.
I ended up dispensing with the jacket and sticking with poly underlayer + wool, works a-ok for now so long as I have my wind-proof mittens. Love those. They're convertible so if they get too warm, I just pull back the top part of the mitten and thumb.