I thought I would explain how canvas and breathable insulation works in extreme cold. FourDog, Mors and others say, "20*F and below, use breathable footwear and outerwear. 20*F and above, use waterproof footwear and outerwear." Sometimes they use 10*F as the breakpoint. Whatever temperature you use, the concept is intuitively obvious. Still, I wondered, why won't other materials work as well? Why canvas? There have been several threads on the...

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