Gortex and other breathable fabrics breath, let water vapor out, when the vapor pressure of the water vapor inside the gortex is more than the water vapor pressure outside the gortex. The energy to evaporate sweat and push it across the gortex membrane is about 600 Calories per Liter of sweat. Paddling at a moderate rate we will sweat about 1 liter per hour. Some of that sweat is sensible, as wet insulation inside the dry suit, but we also lose moisture through our breath and exposed skin. As long as we are working hard enough that the heat loss is less than or equal to our heat production we will feel comfortable or warm. When we stop paddling, heat production is reduced and heat loss remains high or possibly increases with increased exposure. While at rest, once the excess sweat is evaporated and if the insulation layers on the body are sufficient we will stop cooling and maybe even warm up. I think the coldest air I have been paddling in was around -5 F (-20C) Under those conditions when I stopped paddling I was very cold until I got additional insulation on my core. Although I have never paddled in a non-breathable drysuit I would expect that the laws of physics would still apply and that temperature reduction due to radiant, convective and evaporative heat losses along with reduced heat output would result in my feeling cold unless I put on additional layers while I was resting. I would also expect that insulation under gortex would dry out at low to moderate exertion levels while insulation under a sealed drysuit would remain damp. The dry insulation under the gortex should with time, be a better insulator than the insulation under the sealed drysuit. Dana Dickson *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:33:28 PDT