I need to know if I have to change the duck system on my ac because it is made of sheetrock no tubes or flex

Is this the return air? I have never seen this done with the supply.

No this the supply air, it's a box of sheetrock and the return goes through it

Ok how many supplys come form this? Is it falling apart?

There is 1 supply and 1 return, no it is not falling apart my concern is the sheetrock box, would using flex pipes cool my house better and

Well that depends. Is this one supply really large? Or do you have lots of others in the house? If so what are they connected with?

No there's only one and it looks like to be 12 inches round

Round made of sheet rock? Are you sure it is not metal wraped in asbestos?

Either way, then yes I would recommend getting ride of it and flexing or round hard pipe over to it.

I'm sorry misunderstood your question supply goes into this sheetrock box it is 3 feet by 17 feet

OK, just to make sure I am on the same page as you. The suplly comes off the furnace with 12 round pipe that goes to this big sheet rook box then has just 1 big supply registar upstairs?

My ac is on the roof, in the attic I can see 2 hoses, the cold air goes into the sheetrock box and there are vents to all the rooms from this sheetrock box ,the other hose [return air] goes through the sheetrock box back to the ac on the roof, I can see when I took off one of the vents from inside the room

OK I got you now so this rock duct is in the attic or exsposed? I would say yes it would be much more effanct to be metal duct wrapped with bubble wrap. The sheetrock is probably losing lots of air.

Thanks what about flex tubing

Yes you can use flex duct but you will still need some sort of metal box to take them all out of and to put the tube coming threw the roof to.