Ivan Vegvary wrote:
My attic will be insulated on November 30 of this year. They will
blow in 24" of insulation. I have questions about the existing
ductwork. (Ductwork is 10 and 12 inch flexible insulated ducts)
Presently the ducts are laying within the ceiling joist cavity. When
they blow in the insulation, unless they take special care, it is
likely that the bottom quarters of the round ducts might end up with
little or no insulation. In many cases the ducts are 12" nominal and
fill up (because of the extra large outside diameter) most of the
14-1/2" 2"x6" joist cavity. Ergo, the insulation will not be blown
under the duct. However, there will still be a total of 24" of
insulation, approx. 10" of it covering the entire duct.

Question: Air (when not in motion) is a reasonable insulator so I
should leave things alone. Alternatively, it would take very little
work to simply place slats under the ductwork so they sit above the
ceiling joists, allowing them to fill the entire joist cavity.
Obviously, by raising the ducts six inches, I would be getting less
insulation on top of the ducts.

Does any of this matter? Am I wasting my time thinking about this?
BTW, my contractor is very cooperative and will do whatever I ask. He
will even raise the ductwork upon slats at no charge to me.

Opinions greatly appreciated.

Thank you,

Ivan Vegvary
One thing to think about...
I learned by accident that insulation is HEAVY.
IN particular, cellulose insulation looks cost effective, but
is heavier than
fiberglass, BUT as it ages, it absorbs moisture and becomes
MUCH heavier. Depending on the construction of your ceiling
and how well it's attached, this may become an issue.
I was planning a DIY cellulose installation. Glad I didn't.

I'd at least ask the question of your contractor.