it really depends on where you live in the USA
and what codes you have to abide by....
and how big a project are you talking about here?
in Indiana, all we got to do is get one 1 1/2 pvc vent stack
with everything tied into it out the roof of almost any normal size
house and basically its ok (almost too easy) If we run two 1 1/2
vents out the roof its considered almost like we have done an extra good job..
So go find out what code you have to live by and take it from there