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.
If there is mold in the ductwork then I would replace it. Otherwise alot depends on conditions and sizing. That can only be told by looking at the system.
If it was my house and 30 year old duct in crawlspace I would replace it when new system goes in.
I too have a new Trane system ...and I too am having ductwork done.....but not for mold or mildew reasons. My system works great, I have dampers closed to air balance the system throughout the home and all would be good if not for the static pressure. My high static pressure is due to my ducts being undersized for my new trane system. The fan has to overcome the static pressure of the small ducts and uses about twice the electric in the process.
If your system is meeting your comfort needs and you do not smell mold or mildew and your static pressure is not too high what would be the reason to change the duct?
Other than mold, which I haven't pulled anything apart to check, I am looking to improve my efficiency. For a home built in the late 70's I am sure the insulation is minimal and the seams and joints not as good either. It seems a shame to buy an efficient unit and not address the entire system. I have 13 vents in my house and the plan was to increase the size from 6" to 7" in my den which seems to have a dificult time keeping up with the rest of the house. I would assue that the contractor would make sure the sizing of the lines would be adequate for the unit sized for your house.
Don't assume the new duct will be sized correctly ,anymore then assuming the old ducts are sized correctly.
Testing show 70% aren't sized correctly.