python01

I wonder why there is always space left between duct and joists in the basement?
Would it be ok to mount duct right against the joists if it is being replaced? Or is it due to vibration from the furnace or some other reason?

paul52446m

You are right, it is because of vibration. People walking across the floor will make the ducts rattle , so never put the ducts up to the joist. Paul

joecaption

And any vibration in the blower system in the air exchanger will be applified like a speaker box.