That looks close, for ductboard, might be a little noisy for metal. I hope the entire run of trunk isn't going to be all one size?

Not really sure. I don't have a duct sizing program in order to determine the step down size. There is a ten foot run on one side of the plenum, and a 15 foot run on the other, as it is right now. The ductboard is 10x12, I think. It seems ok downstairs, upstairs doesn't seem to be putting out adequate airflow.

This post was edited by Jackfrost069 on Thu, Feb 28, 13 at 17:58

lot of work for a not really sure install.

"I hope the entire run of trunk isn't going to be all one size?"

I wondered about that myself.

why not get advice from a pro in your area who
can visually acess what you have??

what is the reason for removing old trunk line?
is poor air flow upstairs something new?

best of luck.

Thanks for the follow up, guys! No, the airflow problem upstairs has always been a problem. I'm not really comfortable with ductboard, I've heard it can release fiberglass fibers into the air. I'm thinking of having someone come out and take a look at it for me.

when you work with ductboard, cutting into
it, it releases fg particles. once installed
this doesn't happen..unless duct board
is cut into.
if it has been there for a while, is in good
shape, and performs well...why change it??

ductboard plenums have been around
a long time, and are still made on site
in new installs.
it is a good product.

Instead, invest that $$ into solving air flow issues.
sealing ductwork has immediate effect & pays
for itself quickly.

best of luck.

Hey, thanks a bunch for the help! Greatly appreciated!