"Insulations with high clo values, like down, are very fast acting. A garment with a high clo value, once on, traps your body heat very quickly. In comparison, insulations with high loft, generally have a lower clo for a given weight. The higher loft takes longer to heat the insulation and feel the insulation warm, but there is the potential to trap a lot of heat. Down being the ultimate combination of both clo and loft."
That doesn't make sense to me, but I'm not an expert:
"Insulations with high clo values, like down, are very fast acting"
clo is a unit of insulation, like R value for residences. Any insulation can achieve a specific clo value if you select the right thickness of that insulation.
Some insulations have a higher clo per weight - down is best, Primaloft One is not quite as good, Apex or Primaloft Sport are a little less.
Some insulations have a higher clo per thickness (loft) - Thinsulate is better, other synthetics are less, down is worst.
"A garment with a high clo value, once on, traps your body heat very quickly."
As a possibly ridiculous example, if a garment is twice as thick, it will have twice the clo value, but take longer to warm up.
High clo per weight would tend to warm up faster. To simplify, the heat capacity of an insulation is related to it's weight. Water or metal as an extreme example, is very heavy and takes a long time to heat up. Down has a higher clo per weight so it takes less time to warm it up. Higher loft synthetic like Primaloft One takes longer to heat up that down. Other synthetics take longer than PL1. etc.
Maybe they should just say that down heats up faster and leave it at that.
It just bugs me when they come up with some bogus explanation.
Maybe I shouldn't worry about this - argue about politics or something.