I will get the 1/2" foil faced insulation. Glad you mentioned installing it with the foil facing OUTWARD as I thought it might be best to place the foil against it to keep the heat/cool in the duct and maybe installing another layer the opposite way so that foil would be against the duct as well as toward the outside. I'll stick with the one layer and put the foil on the outside rather than against the duct.
Thank you for reminding people about the foil tape rather than duct tape. I have that conversation with many people who wonder why they call it duct tape then. I just tell them that things get names and other things that are better sometimes come along but the old name sticks in people's minds. Foil tape was my plan.