On Tue, 30 Oct 2007 11:41:37 -0400, "Nancy Young"
wrote:

Do you think there is any reason why the vent pipe can't be a
rectangular shape rather than round?

Is there a good reason why vent pipes usuallly are round?

Nancy, Your stove fan vent pipe can be any shape you want. But they
are often traditionally round to make cleaning more effective. That
may sound strange since most home owners never clean their vent
ducting.

caveat: In today's litigious world you may want to check your local
building codes, just to be on the safe side.

And yes getting to the outside world with ducting can be a real
hassle. People often add soffits just to hide the vent ducting. But
I've also seen people put the round spiral ducts out in the open and
paint them as a decoration.

Joshua