Thanks in advance for your input. We are in Phoenix. Our attic has the sheet metal type of ducting. It has blown in insulation over the ducting. We have the ducting exposed right now (blown in insulation moved to the side) and there is also no foil tape or mastic on the seams. The unit is a roof top HVAC, 2 ton. There is probably about 20 feet of duct and you can only get to the top and sides of it.
What is the best stuff to wrap the ducting with? Foil tape and mastic on the seams? Anyone use foam board cut to size? Home depot sells R6 duct insulation but not sure if that is enough of an R value.
I can tell you what worked for me... I am in tempe so it should work for you.
I covered mine with two layers of r13 24 inch wide bats. Then I covered all that with a radiant barrier. I also added some insulation in side of the package unit on the roof.. doing all that really helped!!!!