When you do your pricing on the duct work, consider the fittings cost first, that's where most of the dollars go. If you wind up with PVC, be sure to get the right stuff.....since it's called by so many names (and Skippy Stockboy usually doesn't know any of them) look for the proper markings on the side: you want ASTM D2729, that's the thinnest, least costly pipe. You can get by with 3034, but it's heavier, costs more, and is beyitch to try and hang from the ceiling by yourself (DAHIKT).