My current ductwork consists of a main trunk for supply that is rigid, with flex off of it (ranging from 4 to 6") to the supply registers. All of the returns are flex.
I have read on these pages that each usually has a different optimal air velcoity.
Since I am redoing my main trunk as part of finishing the basement should I just go ahead an get rigid ductwork throughout? So far the bids have included reusing the flex and just reworking the main trunk to get some more headroom.
I dont want to go cheap on reuse of flex if mixing them is a bad idea.