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Old 01-10-13, 01:07 PM
  #14  
shepherdsflock
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Originally Posted by erig007 View Post
This is exactly when things don't go as planned that the vapor barrier jacket shine.
Staying dry is a very good solution. But don't mix being wet with a breathable system and wet with a vapor barrier system as results are not the same.
I used this technique many times in very cold days when i was wearing my wet merino wool base layer and i knew i had to do a short stop at the shopping mall (nearly similar result than a stop due to a chain link broken) the feeling on my way back was so much better than without the vapor barrier layer overheating problems excepted
The vapor barrier jacket isolate your body heat from the environment radiative heat transfers excepted. During your ride your sweat have accumulated sensible heat like batteries accumulate energy when you stop you use this energy to stay warm and as your body is supposedly isolated from the environment and with the inertial heat factor you should generate enough heat to stay warm..
At 20F differences are not so noticeable but at -20F or -30F and a wet base layer you notice differences. If you're perfectly dry then no need to go for the vapor barrier jacket but if you're not in this situation like if you naturally sweat well above average or you pushed too hard or one layer gather sweat or whatever other reason then that's when the vapor barrier jacket shine. Now if for whatever reasons you lose the accumulated heat inside the vapor barrier layer it will be harder to get the heat back as inertial heat act in both ways staying warm but also getting your heat back. In this case you can either temporarily increase your work out to warm it up back or get rid of the cold sweat. This situation never happened to me though.
The "vapor barrier" jacket as erig calls it, does two things for you: it keeps the wind outside from cooling and evaporating your sweat too quickly (causing you to feel cold), and it traps your body heat (keeping you warmer). I use a Cannondale rain shell jacket that I picked up about 6 years ago and it is wonderful for cold weather riding. I just wear my Under Armor insulated shirt under it and I'm good to about 0 degrees F. Down to about 15 degrees F I have to unzip the armpit vents to help eliminate excess body heat. Barrier jackets like these are very effective, but if you go shopping for one, make sure it has ventilation zippers so you can adjust airflow as temperatures increase. Otherwise, on warmer days, you'll be a sweaty mess when you arrive at your destination.
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