I have a main trunk supply line that is round and 16 inches in diameter. My return line is also that same size. I am thinking about wrapping the ducts with r-13 and using a black or clear plastic from Lowes to wrap on top of the insulation as a vapor barrier. My ductwork is in a crawlspace. I really don't think the kraft paper faced insulation is a good idea due to fire/et c.
I know I can buy special insulation for ductwork, but it is more expensive and does not give as high of an r-value.
Is this advisable/doable? If so would you use clear or black plastic?
Thanks for the help!