Best way to seal/insulate square ductwork?

[CraigT]

My furnace is in a 12' X 20' storage room in my basement. Another room in the basement that is a little larger is my Home Theater set up and my computer desk. I have no vents open in my basement, yet the leakage from the ductwork is enough to heat it in the winter and in the summer makes the basement like an icebox. I have often thought that the furnace would be more efficient if I could seal and/or insulate the square and round ductwork in the basement. I have seen the air bubble foil wrap, but wonder if this would be a good solution for the square ductwork? Also, how would this best be accomplished yet still allow for duct cleaning every few years?

[alvinamorey]

They sell foil covered fiberglass insulation in rolls just for that use. You DO NOT want to use anything that is not made for this purpose as a fire could start, at least nearest the furnace. You apply this stuff with a special aluminum duct tape.

To make for easy cleaning, leave a few gaps where you open the ducts. Maybe cover them with something easy to remove. A piece of this same insul. held in place with steel wire would be one way.