We want to remodel our kitchen, but a large 9" round chimney vent to
our roof connected to our furnace and hot water heater runs through
one of our cabinets, taking up a fair amount of space. In the
remodel, we are putting in a new wall to separate the kitchen area
from the dining area that is next to the existing chimney.

A handy friend of mine said that I could convert the round pipe to a
rectangle (3 x 10) that could run through the drywall. However, the
heating contractors I've spoken with on the phone are saying I can't
do this and I need a new furnace and hot water heater to direct-vent
the air out.

My concern is that these heating contractors are mostly trying to sell
a product rather than really telling me what I could do more
economically. I'm also concerned that if I follow my friend's advice,
I might not be up to code (and could potentially endanger my
family...).

I'm not very handy and would appreciate any advice.