Once the main leaks were all handled, I then took to insulating the air handler on the outside and the supply ducts.
I chose to use 1 inch Polyiso board insulation. I chose 1 inch because I needed some flexibility. I used 5-6 sheets of this and placed it all over both the handler and the supply ducts. I sealed the corners using the same duct tape.
This part of the project took many hours of cutting and measuring. I found over time that using a putty knife blade is the preferred way to cut the stuff as a sheet-rock saw makes a mess. I did not care as it’s all in the attic but it’s much easier and the static electricity will sometimes make the other bits stick to you and your clothes. There is also a disturbing smell when you cut the poly iso and that made me a bit nervous as the the word cyanide in the full chemical name of the insulation.
Anyway, the A/C ductwork was now covered with R-6 insulation. A good start and coupled with the sealing of the leaks, a giant improvement.