Sealing duct boots – GreenBuildingAdvisor

I’m working on an HVAC update now, and planning on doing both. I’ve asked my HVAC contractor to seal that can-to-drywall connection when he installs the actual ducts, and he says he will use mastic tape to create the best seal possible from the attic side. I also plan on finishing that connection with metal tape of my own from the interior. It will all be hidden by the register cover, ultimately, but it’s another piece of mind to keep the attic in the attic.

It’s worth nothing that working overhead on a ceiling is always a fiasco, and if you have access via the attic — and it’s not hot — that is probably the simpler way. Working “down” is much more comfortably, physically.