I’d like to bump this thread back up as I just re-read it and it’s very insightful into the basics of insulation physics. If uts new to you, its worth a read imo.
In addition to richard’s insight, I also enjoy Stephen seeber’s work on this topic recently.
My takeaway is We’re really spoiled with UL insulation now days. So many more choices compared to just 10 or 20 years ago