This weekend I'm going to spend some time in my crawl space tuning up my duct system (flex duct). By tuning up I plan to ensure runs are adequately supported and well connected to junction boxes. I also plan to check for any leaks and repair as necessary. I also want to insulate the plenum from my downdraft AH that goes from garage into crawlspace.
I see that Nashua has a duct tape that's code approved for flex duct called 557. How does it hold up over time? I am generally not a fan of duct tape for ducts but will this stuff actually work?? I also bought some king size tie wraps to reinforce joint connections.
Also what's the best insulation for T junction boxes and plenums. I see rolls of 12" self adhesive insulation but R value is only 3 or so. Would a couple cans of Great Stuff be better at encasing metal connectors with insulation?
P.S. Unfortunately I've had previous problems with flex duct seperations due to a lazy contractor who failed to use good tape, failed to use tie wraps, and failed to adequtely support the flex runs.