My concern with Tyvek tape is, would it be a fire hazard?

I know I can put my hand on ducts and not burn myself, but, would you
like to explain to the insurace company that, because you were too
cheap to spend an extra quarter on a roll of tape that is designed for
the purpose of heat ducts vs combustable tape.

I can guarantee that duct tape does dry out and break down.

Mike Holmes on Homes (canadian show) talked about tape too. They were
repairing an issue with the heat not getting to the third floor.

10% of the heat was lost in joints alone!! do the monthly math...
worth the trip to the store and back.

Busting the drywalls reveiled that a pipe was disconnected and was
just blowing in the ceiling and walls.
Since i'm on it, they also added insulation around the ducts, which I
would love to do since my basement is not finished ... yet.
cln