I have made multiple prior posts explaining that NO synthetic garments that I lab tested, unlike the down garments, were close to their theoretical Iclo specification. I don’t doubt the value of the synthetic insulation’s specified Iclo at the time of manufacture, BUT after being manufactured into a garment and boxed and unboxed during distribution, they test, on average, 51% of their theoretical values. This chart is a portion of one of my many prior posts on this topic from a couple of years ago:
About the same time that I did these tests, BPL was manufacturing synthetic garments for UL backpacking. They were also recommending that synthetic garments and quilts be used during their courses. So, TO BE POLICTIALLY CORRECT, after first posting multiple times that ALL synthetic garments that I tested averaged about ½ of their theoretical Iclo value, I posted all subsequent synthetic garment’s Iclo values based on their theoretical specs. For my personal sustained-wet-weather use, I select garments based on the -51% of Iclo spec. lab test results. I try to not dissuade others from making their decisions based on the manufacturer’s specifications if they choose to do so.