Discussions of active insulation always focus on the key advantage of breathability, which supposedly affords a wider temperature range compared to traditional jackets with tighter shells. How come no one mentions that most traditional down and synthetic puffy jackets come with the ultimate in breathable features, a full-length zipper? (The same principle applies to rain gear, where pit zips are often more important than fabric breathability.) And if unzipping your jacket to dump all your core heat isn’t enough, just take it off. Why would I want an “active insulation” garment that is heavier and bulkier for same warmth? (The only exception would be for sports enthusiasts, like racers or mountain climbers, who may not have time to adjust their jacket.) Am I missing something?
