If the non steel ductwork is the fact that soiled you must just have it changed AND sealed. Also most duct programs are not quite nicely made. Seek out right sizing and don't go inexpensive with one or two intakes (return grills) You would like them by means of-out http://east-irvine51690.blogzag.com/17803666/the-5-second-trick-for-air-duct-cleaning-orange-county