I currently have a forced hot air system in my home with a small maze
of output & return vents in the basement.
Since the oil heating unit still works (at 80% efficency mind you),
when I go to upgrade it I want to add central air as well as replace
all the metal ducts with a smaller PVC (2" or so) so that I could put
a drop ceiling in the basement. I want to set it up as an
entertainment room/area but cannot do so with a 7 1/2 foot ceiling
with only 6 foot of clearance in some areas because of the ducts.
What are the drawbacks in using the forced PVC system vs. metal ducts?