I am finishing my basement and there are large ducts down the middle of the room. I am wondering if there is technology (other than replacing with mini-ducts with high pressure system) or mechanism I can use to reduce the size of the ducts. Can the air go through the joists? Are there special ducts for doing this? It appears the intake runes through the wall and joists at some points. Can this be done for heated/cooled air?

Thanks.

I've seen some house before where there wasn't any space for duct, where they uses foam duct board and lined the joist and the upper floor and closed in the bottom. So that you won't have any leaks and prevent the woodon joist from sweating
And eventually rotting

Nailing tin sheets to the bottom of the joists has long been a common technique for the return side. If the supply ducts are aren't already up between the joists, I see no problem moving them there, again commonly done where the duct runs along the joists. Where the ducts must run crossways to the joists, I don't see a good solution. You can't cut big holes in the joists. You could go to smaller ducts, but it could require much higher pressure to move the air. I think air works the same way as water and a 1'2/ pipe has 16-32 times as much pressure drop for the same flow as a 1'' pipe. This site is not about going to a professional for help, but reducing the duct sizes is nothing I can help with.