What's the best solution to my A/C return problem?

My house had a mold issue that has been resolved. However, due to this problem, I now have mold growth inside the return duct of my A/C system. It is a metal duct that is lined with fiberglass insulation. It is visibly contaminated and creates an odor that is being spread throughout the house.





Which is my best option:


1. Replace the insulation with new fiberglass or other duct liner.


2. Remove the insulation and insulate the exterior of the duct.


3. Pull out the whole return duct and replace with one made of fiberglass duct board.


4. A completely separate option that I have not covered since I am not a pro.





I would hire a professional but the cost is through the roof. I can handle this job since I am a pro in other trades. Just another skill to add to the ever growing list. Time is of the essence though because I am not running the unit at all to avoid "the stinkies" and, being in the South, the heat will not hold off much longer. Thanks for any input.

What's the best solution to my A/C return problem?
i dont know what services are offered in your area or the cost, but have you looked into cleaning/mold removal? i am goining to assume that you have, i have some experience in hvac systems and my recommendation is to replace the duct work with metal duct work and insulate it from the outside. it is easily cleaned if your mold returns. also did you hire someone to remove the mold? if so why didn't they take care of the the mold in the ducts?? anyway hope this helps. if you need more feel free to ask me
Reply:Remove all contaminated ductwork, replace with regular galv. duct, and insulate the exterior if you want. (it's a return, why insulate?)
Reply:Initially, the knee-jerk reaction would be to answer with option 2. However, to remove the lining would require you to tear-out the line anyway. And if you have to do this, you need to go back with new stuff. ductboard is the most cost-effective material. And it's easier to work with (you can hide mistakes, which is impossible with rigid sheet-metal!). I have learned through mold removal courses that the only sure-fire way to rid the home after contamination is a new system. Even though you say you have solved the problem, in reality you're circulationg mold spores around every minute your fan runs.
Reply:Either option #3 OR haave a HVAC company make you a new insulated return in their shop and you can install it.
Reply:you need to install an ultraviolet light in the return system.
Reply:I would replace the duct and use external insulation if any since it is only a return and not a supply. Experience with ductboard and I wouldn't recommend that, it's difficult to mess with and you get a lot of insulation all over you, also easy to break the board if your not careful.


When I moved into my house I went through and replaced all the supply ducts in my house with round sheetmetal externally insulated for the 2 main lines and insulated flex off the main to the registars. My return is nothing more than 3 10x36 grills that lead directly to a void under the A/C unit itself.
Reply:Have you been able to tell exactly how for the mold spread is? If it is some place where it is accessable there are a couple things you can try. Try to keep the humidity in your house under 45%, ultraviolet light also kills mold, and the last thing I can think of is keeping the temperature under 75 degrees, if you can't seem to halt the growth with that, you might want to remove the insulation, and wrap the outside of the box.