Join Date: Jan 2001
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I'm not an expert, buy I have a theory.
Any jacket adds warmth and thus more perspiration. Offshore jackets are more durable than others, but tend to be heavier and provide yet more warmth.
I have a really light jacket from Pacific Trail (since acquired by Columbia) that works really great in the summer, but doesn't provide any warmth and aren't very useful when it's colder. For that I have a Gill jacket that's heavier. When I got the light jacket, I also got lightweight bib overalls. The waterproofing wore of of the seat too fast and they began to leak, leaving me with a wet butt. I've since replaced them with a pair of Gill bibs that work much better. They're warmer, so I only put them on when it's really pouring.