I am trying to decide if I need to replace my main trunk and duct system or use the existing. I have recieved quotes from 3 different companies and everyone has a differient opinion. The house is 30 years old brick ranch with crawl space. The main trunk is on the ground and has been that way for many years. All is galvanized pipe with wrap which I am sure needs replacing. I have concern that mold and dirt are present in the duct and could never be cleaned completly and with a new Trane system and inproved efficiency unit I should bite the bullet and have all replaced. I would appreciate any advise.