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Duct Insulation

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I need to insulate my duct-work.

The individual runs for each room is easy enough but, not really sure how to go about the main "trunk" run. It drips like a spring rain shower in the summer with the cold air running through it! It's butted up against the floor joist making it difficult to completely encapsulate it to prevent the air making contact with it ~ producing the condensation.

I could cover all but the width of each floor joist through the span of the duct. I fear that the insulation would just get wet and create an even worse mess than I began with!

Any suggestions on the type of insulation to use, fiberglass or foam wrap etc, and should I find a way to un-mount it at least enough to be able to fully wrap it?