[gregzoll]

What size are your joists? Keep in mind, changing the ducts, can change the aspect of how efficient your unit is. Change the size of the duct work, you can open up a huge can of worms. With that, you could find that the upstairs no longer heats or cools as it should, or could cause short cycling.

 

[ctote]

Sounds like something I should hire a professional for. The ductwork is non-existent currently in the basement - the unit supports zoning, so the basement would be on its own zone.

 

[gregzoll]

I would, especially with zoning involved.